A few upgrades for my '78

The engine builder provided a dyno graph for the engine that I suspect came out of desktop dyno. Since that's all I have to go off of right now, I'm going to assume that it's good enough to ballpark from and run with it. At 1500rpm, the engine should produce better than 350 ft. lbs of torque which means that it should cruise just fine at 1500 rpm and I should try to get my cruising rpm between 1500 – 2000 rpm for the 60 – 80 mph range.

I made a little excel spreadsheet to put all of this in table form but it doesn't keep the formatting when I copy and paste. So here's the info in paragraph form..

So.. As it currently stands with the stock Saginaw transmission and 3.36:1 rear end…
From what I read, the Saginaw used in the Vettes had 2.85, 2.02, 1.35, and 1.00 ratios. Assuming a 27 inch tire, the 60 mph cruising rpm would be 2508 rpm and 80 mph would be 3345 rpm. The first gear final drive ratio is 9.58:1, which is close to the goal of a 10:1 first.

If it had an M21 with the 3.36:1 rear end…
The trans would have 2.20, 1.64, 1.27, and 1.0 ratios. Assuming a 27 inch tire, the 60 mph cruising rpm would also be 2508 rpm (1:1 4th) and the 80 mph rpm would be 3345. The first gear final drive ratio is 7.39:1, which is a good bit below the 10:1 goal.

A T56 with the 3:36 rear end…
Trans gearing for all but a few T56's is 2.66, 1.78, 1.30, 1.0, .74, .50. The 60mph cruising rpm would be 1254 and 80 mph would be 1672. The first gear final drive ratio is 8.94:1, which is better than the Muncie but still not the desired 10:1.

A T56 with 3.73 rear end would have the same gearing as above. The 60 mph cruising rpm is 1392 and 80 mph is 1857. The first gear final drive ratio is 9.92:1.

A T56 with 3.90 rear end would have the same gearing as above. The 60 mph cruising rpm is 1456 and 80 mph is 1941. The first gear final drive ratio is 10.37:1.

Comparatively, a Richmond ROD as sold by Jegs has 3.28, 2.13, 1.57, 1.23, 1.00, and .76 gear ratios. With a 3.36:1 rear end, the 60 mph rpm would be 1907 and 80 mph would be 2542. The first gear final drive ratio is 11.02.

A Richmond ROD with the ratios above and a 3.08:1 rear end would run at 1748 rpm at 60 mph and 2330 at 80 mph. The first gear final drive ratio is 10.10:1.

The Richmond has the advantage that you can call them and basically order it with what ever ratios you want. The downside is that it is expensive.
 
Last edited:
excellent work on calculating ratios and optimal ratios - it really pays off when you have a car that seems to always be in its "sweet spot"

I also understand they're expensive - like twice as much as a ST-10; but it's twice the transmission... seriously. After the 6 speed in my GTO, I wouldn't own another t-56 (willingly)

as for LS gas mileage. They are an awesome motor, great power, incredible strength. they are not, however, good on gas. I have an 06 GTO with a 6 speed and it gets 15 city, 18 highway.... the Corvette gets a bit better because of aero and gearing. That said I can take the Corvette's lunch in stoplight wars because I have 3.42 gears vs. the Corvette's 3.23 or .08 (similar year Corvette)... and don't talk to me if you have a Camaro - they're ssssllllloooooowwwwwww (compared to the GTO which is 600 lbs lighter)

which is why I'm going to get a v8 H3 hummer (again) - for the better fuel economy (yep, I said it, I'm going to a Hummer to get better mileage) :3rd:
 
I just had a thought based off of another post on here.. A 3.90 or 4.11 rear end ratio is not desirable since that means pinion speed is way up... and heat. So that's just another plus for the Richmond ROD since it is geared lower and doesn't necessitate the numerically higher rear end ratio.

Also, the calcs show that I'd have to change the ring and pinion to get the desired final drive so the extra cost of the ROD is negated. Well, I still should rebuild my diff with new bearings but I think the ratios with the ROD and the 3:36 rear end make a decent combo.
 
Last edited:
LSx gas mileage ??? I've put almost 100000 miles on my LS1 ('99 Z28) and got 25 mpg on the highway, now with my C6 and the LS2 (6spd) I get 20 mpg average, 26mpg highway ....computer says 30-32mpg when doing 65mph steady ..... I think its really great mpg considering its a 400 hp V8
 
I was really bored.. had some extra rum.. so I wrote up this short code for calculating speed @ different RPM's based on the different final drives and transmissions.. though I conveniently left out the 5 speeds. I'll eventually turn this into PHP so it can be hosted. But.. if you're so inclined.. copy and paste it into a txt file with the extension .xml and your web browser will run it.

I wish I did this all the time.. I'm not very good at it.

HTML: 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
	  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>

    <title>Gearing, RPM, and Vehicle Speed Calculator</title>
		<script>
    	function calculate()
				{
				 	var first = parseFloat(document.getElementById("firstgear").value);
					var second = parseFloat(document.getElementById("secondgear").value);
					var third = parseFloat(document.getElementById("thirdgear").value);
					var fourth = parseFloat(document.getElementById("fourthgear").value);
					var fifth = parseFloat(document.getElementById("fifthgear").value);
					var sixth = parseFloat(document.getElementById("sixthgear").value);
					var wheel = parseInt(document.getElementById("wheeldiameter").value);
					var rpm = parseInt(document.getElementById("maxrpm").value);
					var diffy = parseFloat(document.getElementById("diff").value);
										
					document.getElementById("firstFinalRatio").value = finalRatio(diffy, first).toFixed(2);
					document.getElementById("first60").value = maxRpm(60, diffy, first, wheel).toFixed(2);
					document.getElementById("first80").value = maxRpm(80, diffy, first, wheel).toFixed(2);	
					
					document.getElementById("secondchange").value = percentChange(first, second) * 100;	
					document.getElementById("secondFinalRatio").value = finalRatio(diffy, second).toFixed(2);
					document.getElementById("second60").value = maxRpm(60, diffy, second, wheel).toFixed(2);
					document.getElementById("second80").value = maxRpm(80, diffy, second, wheel).toFixed(2);	  
					
					document.getElementById("thirdchange").value = percentChange(second, third) * 100;
					document.getElementById("thirdFinalRatio").value = finalRatio(diffy, third).toFixed(2);
					document.getElementById("third60").value = maxRpm(60, diffy, third, wheel).toFixed(2);
					document.getElementById("third80").value = maxRpm(80, diffy, third, wheel).toFixed(2);
					
				  document.getElementById("fourthchange").value = percentChange(third, fourth) * 100;
					document.getElementById("fourthFinalRatio").value = finalRatio(diffy, fourth).toFixed(2);
					document.getElementById("fourth60").value = maxRpm(60, diffy, fourth, wheel).toFixed(2);
					document.getElementById("fourth80").value = maxRpm(80, diffy, fourth, wheel).toFixed(2);
						
					document.getElementById("fifthchange").value = percent = percentChange(fourth, fifth) * 100;
					document.getElementById("fifthFinalRatio").value = finalRatio(diffy, fifth).toFixed(2);
					document.getElementById("fifth60").value = maxRpm(60, diffy, fifth, wheel).toFixed(2);
					document.getElementById("fifth80").value = maxRpm(80, diffy, fifth, wheel).toFixed(2);	
					
					document.getElementById("sixthchange").value = percentChange(fifth, sixth) * 100;
					document.getElementById("sixthFinalRatio").value = finalRatio(diffy, sixth).toFixed(2);
					document.getElementById("sixth60").value = maxRpm(60, diffy, sixth, wheel).toFixed(2);
					document.getElementById("sixth80").value = maxRpm(80, diffy, sixth, wheel).toFixed(2);	
				}//end function calculate
				
				function maxRpm(speed, diff, gear, wheel)
				{
				  return ((diff * gear) * speed * 336)/wheel;
				}//end function rpmAt60
				
				function finalRatio(diff, gear)
				{
				  return diff * gear;
				}//end finalRatio
				
				function wheelDistance(wheelDiameter)
				{
				  return (wheelDiameter/12) * 3.14159;
				}//end function wheelDistance
				
				function percentChange(ratio1, ratio2)
				{
				  return (ratio1 - ratio2) / ratio1;
				}//end function percentChange
				
				function getRatio()
				{	//Transmissions and ratios
					var ratios = [ [0, 0, 0, 0, 0, 0], 
					             [2.85, 2.02, 1.35, 1.00, 0, 0],      
				               [2.52, 1.88, 1.47, 1.00, 0, 0],      
											 [2.20, 1.64, 1.27, 1.00, 0, 0],      
											 [2.43, 1.61, 1.23, 1.00, 0, 0],      
											 [2.66, 1.78, 1.30, 1.00, .74, .50],  
											 [3.28, 2.13, 1.57, 1.23, 1.00, .76], 
											 [0, 0, 0, 0, 0, 0] ];										 	
					 
					 var trans = parseFloat(document.getElementById("transmission").value);
					
					  document.getElementById("firstgear").value = ratios[trans][0].toFixed(2);
					  document.getElementById("secondgear").value = ratios[trans][1].toFixed(2);
					  document.getElementById("thirdgear").value = ratios[trans][2].toFixed(2);
					  document.getElementById("fourthgear").value = ratios[trans][3].toFixed(2);
					  document.getElementById("fifthgear").value = ratios[trans][4].toFixed(2);
					  document.getElementById("sixthgear").value = ratios[trans][5].toFixed(2);

				}//end function getRatios
    </script>

  </head>
  <body>
	  <form>
		  <table border = "1">
			  <tr>
				  <th colspan="6">Vehicle Data</th>
				</tr>
				<tr>
				  <td>Wheel Diameter: </td>
					<td><input type="text" id="wheeldiameter" /></td>
					<td>Max RPM: </td>
					<td><input type="text" id="maxrpm" /></td>
					<td><input colspan="2" type="submit" onclick="calculate()" value="Calculate"/></td>
				</tr>
				<tr>
					<td>Differential Ratio:</td>
					<td><input type="text" id="diff" /></td>
				  <td>Transmission:</td>
					<td><select id="transmission" onchange="getRatio()">
							  <option value="0"></option>
							  <option value="1">Saginaw 4 Speed</option>
							  <option value="2">Muncie M20</option>
							  <option value="3">Muncie M21 or M22</option>
							  <option value="4">Borg Warner Super T10</option>
							  <option value="5">1994+ T56</option>
							  <option value="6">Richmond ROD</option>
							  <option value="7">Custom Ratios</option>
							</select>
							</td>
				</tr>
				<tr>
				  <td colspan="2"><b>Gear Ratios</b></td>		
				  <td><b>% Change</b></td>
					<td><b>Final Ratio</b></td>
					<td><b>RPM @ 60 MPH</b></td>
					<td><b>RPM @ 80 MPH</b></td>
				</tr>	
				<tr>
				  <td>First Gear</td>
					<td><input type="text" id="firstgear" />:1</td>
					<td></td>
					<td><input type="text" readonly="readonly" id="firstFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="first60"/></td>
					<td><input type="text" readonly="readonly" id="first80"/></td>
				</tr>
				<tr>
				  <td>Second Gear</td>
					<td><input type="text" id="secondgear" />:1</td>
				  <td><input type="text" readonly="readonly" id="secondchange"/></td>
					<td><input type="text" readonly="readonly" id="secondFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="second60"/></td>
					<td><input type="text" readonly="readonly" id="second80"/></td>
				</tr>
				<tr>
				  <td>Third Gear</td>
					<td><input type="text" id="thirdgear" />:1</td>
					<td><input type="text" readonly="readonly" id="thirdchange"/></td>
					<td><input type="text" readonly="readonly" id="thirdFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="third60"/></td>
					<td><input type="text" readonly="readonly" id="third80"/></td>
				</tr>
				<tr>
				  <td>Fourth Gear</td>
					<td><input type="text" id="fourthgear" />:1</td>
					<td><input type="text" readonly="readonly" id="fourthchange"/></td>
					<td><input type="text" readonly="readonly" id="fourthFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="fourth60"/></td>
					<td><input type="text" readonly="readonly" id="fourth80"/></td>
				</tr>
				<tr>
				  <td>Fifth Gear</td>
					<td><input type="text" id="fifthgear" />:1</td>
					<td><input type="text" readonly="readonly" id="fifthchange"/></td>
					<td><input type="text" readonly="readonly" id="fifthFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="fifth60"/></td>
					<td><input type="text" readonly="readonly" id="fifth80"/></td>
				</tr>
				<tr>
				  <td>Sixth Gear</td>
					<td><input type="text" id="sixthgear" />:1</td>
					<td><input type="text" readonly="readonly" id="sixthchange"/></td>
					<td><input type="text" readonly="readonly" id="sixthFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="sixth60"/></td>
					<td><input type="text" readonly="readonly" id="sixth80"/></td>
				</tr>
			</table>
		</form>	
</body>
</html>
 
MYBAD79 said:
LSx gas mileage ??? I've put almost 100000 miles on my LS1 ('99 Z28) and got 25 mpg on the highway, now with my C6 and the LS2 (6spd) I get 20 mpg average, 26mpg highway ....computer says 30-32mpg when doing 65mph steady ..... I think its really great mpg considering its a 400 hp V8
Click to expand...

to my qualifications, I also add I don't live in flat country :)

I'm in a discussion on another forum where I boldly proclaimed that the old SBC gets better mpg then a new one.... and it does. A good example is your Camaro, I had an 89 IROC Camaro with the 5.7, and did quite a bit better then 25 mpg on the highway...

LS1 isn't an LS2. Strangely, my car's computer shows the mileage as lower then it actually is - usually .5 mpg less then what the mileage divided by the gallons indicate. Best tank ever was 22 mpg.... best ever, steady state, cruise on, flat ground (interstate following a river, 65 mph, 20 mph tailwind)...
 
Last edited:
pancake said:
I was really bored.. had some extra rum.. so I wrote up this short code for calculating speed @ different RPM's based on the different final drives and transmissions.. though I conveniently left out the 5 speeds. I'll eventually turn this into PHP so it can be hosted. But.. if you're so inclined.. copy and paste it into a txt file with the extension .xml and your web browser will run it.

I wish I did this all the time.. I'm not very good at it.

HTML: 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
	  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>

    <title>Gearing, RPM, and Vehicle Speed Calculator</title>
		<script>
    	function calculate()
				{
				 	var first = parseFloat(document.getElementById("firstgear").value);
					var second = parseFloat(document.getElementById("secondgear").value);
					var third = parseFloat(document.getElementById("thirdgear").value);
					var fourth = parseFloat(document.getElementById("fourthgear").value);
					var fifth = parseFloat(document.getElementById("fifthgear").value);
					var sixth = parseFloat(document.getElementById("sixthgear").value);
					var wheel = parseInt(document.getElementById("wheeldiameter").value);
					var rpm = parseInt(document.getElementById("maxrpm").value);
					var diffy = parseFloat(document.getElementById("diff").value);
										
					document.getElementById("firstFinalRatio").value = finalRatio(diffy, first).toFixed(2);
					document.getElementById("first60").value = maxRpm(60, diffy, first, wheel).toFixed(2);
					document.getElementById("first80").value = maxRpm(80, diffy, first, wheel).toFixed(2);	
					
					document.getElementById("secondchange").value = percentChange(first, second) * 100;	
					document.getElementById("secondFinalRatio").value = finalRatio(diffy, second).toFixed(2);
					document.getElementById("second60").value = maxRpm(60, diffy, second, wheel).toFixed(2);
					document.getElementById("second80").value = maxRpm(80, diffy, second, wheel).toFixed(2);	  
					
					document.getElementById("thirdchange").value = percentChange(second, third) * 100;
					document.getElementById("thirdFinalRatio").value = finalRatio(diffy, third).toFixed(2);
					document.getElementById("third60").value = maxRpm(60, diffy, third, wheel).toFixed(2);
					document.getElementById("third80").value = maxRpm(80, diffy, third, wheel).toFixed(2);
					
				  document.getElementById("fourthchange").value = percentChange(third, fourth) * 100;
					document.getElementById("fourthFinalRatio").value = finalRatio(diffy, fourth).toFixed(2);
					document.getElementById("fourth60").value = maxRpm(60, diffy, fourth, wheel).toFixed(2);
					document.getElementById("fourth80").value = maxRpm(80, diffy, fourth, wheel).toFixed(2);
						
					document.getElementById("fifthchange").value = percent = percentChange(fourth, fifth) * 100;
					document.getElementById("fifthFinalRatio").value = finalRatio(diffy, fifth).toFixed(2);
					document.getElementById("fifth60").value = maxRpm(60, diffy, fifth, wheel).toFixed(2);
					document.getElementById("fifth80").value = maxRpm(80, diffy, fifth, wheel).toFixed(2);	
					
					document.getElementById("sixthchange").value = percentChange(fifth, sixth) * 100;
					document.getElementById("sixthFinalRatio").value = finalRatio(diffy, sixth).toFixed(2);
					document.getElementById("sixth60").value = maxRpm(60, diffy, sixth, wheel).toFixed(2);
					document.getElementById("sixth80").value = maxRpm(80, diffy, sixth, wheel).toFixed(2);	
				}//end function calculate
				
				function maxRpm(speed, diff, gear, wheel)
				{
				  return ((diff * gear) * speed * 336)/wheel;
				}//end function rpmAt60
				
				function finalRatio(diff, gear)
				{
				  return diff * gear;
				}//end finalRatio
				
				function wheelDistance(wheelDiameter)
				{
				  return (wheelDiameter/12) * 3.14159;
				}//end function wheelDistance
				
				function percentChange(ratio1, ratio2)
				{
				  return (ratio1 - ratio2) / ratio1;
				}//end function percentChange
				
				function getRatio()
				{	//Transmissions and ratios
					var ratios = [ [0, 0, 0, 0, 0, 0], 
					             [2.85, 2.02, 1.35, 1.00, 0, 0],      
				               [2.52, 1.88, 1.47, 1.00, 0, 0],      
											 [2.20, 1.64, 1.27, 1.00, 0, 0],      
											 [2.43, 1.61, 1.23, 1.00, 0, 0],      
											 [2.66, 1.78, 1.30, 1.00, .74, .50],  
											 [3.28, 2.13, 1.57, 1.23, 1.00, .76], 
											 [0, 0, 0, 0, 0, 0] ];										 	
					 
					 var trans = parseFloat(document.getElementById("transmission").value);
					
					  document.getElementById("firstgear").value = ratios[trans][0].toFixed(2);
					  document.getElementById("secondgear").value = ratios[trans][1].toFixed(2);
					  document.getElementById("thirdgear").value = ratios[trans][2].toFixed(2);
					  document.getElementById("fourthgear").value = ratios[trans][3].toFixed(2);
					  document.getElementById("fifthgear").value = ratios[trans][4].toFixed(2);
					  document.getElementById("sixthgear").value = ratios[trans][5].toFixed(2);

				}//end function getRatios
    </script>

  </head>
  <body>
	  <form>
		  <table border = "1">
			  <tr>
				  <th colspan="6">Vehicle Data</th>
				</tr>
				<tr>
				  <td>Wheel Diameter: </td>
					<td><input type="text" id="wheeldiameter" /></td>
					<td>Max RPM: </td>
					<td><input type="text" id="maxrpm" /></td>
					<td><input colspan="2" type="submit" onclick="calculate()" value="Calculate"/></td>
				</tr>
				<tr>
					<td>Differential Ratio:</td>
					<td><input type="text" id="diff" /></td>
				  <td>Transmission:</td>
					<td><select id="transmission" onchange="getRatio()">
							  <option value="0"></option>
							  <option value="1">Saginaw 4 Speed</option>
							  <option value="2">Muncie M20</option>
							  <option value="3">Muncie M21 or M22</option>
							  <option value="4">Borg Warner Super T10</option>
							  <option value="5">1994+ T56</option>
							  <option value="6">Richmond ROD</option>
							  <option value="7">Custom Ratios</option>
							</select>
							</td>
				</tr>
				<tr>
				  <td colspan="2"><b>Gear Ratios</b></td>		
				  <td><b>% Change</b></td>
					<td><b>Final Ratio</b></td>
					<td><b>RPM @ 60 MPH</b></td>
					<td><b>RPM @ 80 MPH</b></td>
				</tr>	
				<tr>
				  <td>First Gear</td>
					<td><input type="text" id="firstgear" />:1</td>
					<td></td>
					<td><input type="text" readonly="readonly" id="firstFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="first60"/></td>
					<td><input type="text" readonly="readonly" id="first80"/></td>
				</tr>
				<tr>
				  <td>Second Gear</td>
					<td><input type="text" id="secondgear" />:1</td>
				  <td><input type="text" readonly="readonly" id="secondchange"/></td>
					<td><input type="text" readonly="readonly" id="secondFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="second60"/></td>
					<td><input type="text" readonly="readonly" id="second80"/></td>
				</tr>
				<tr>
				  <td>Third Gear</td>
					<td><input type="text" id="thirdgear" />:1</td>
					<td><input type="text" readonly="readonly" id="thirdchange"/></td>
					<td><input type="text" readonly="readonly" id="thirdFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="third60"/></td>
					<td><input type="text" readonly="readonly" id="third80"/></td>
				</tr>
				<tr>
				  <td>Fourth Gear</td>
					<td><input type="text" id="fourthgear" />:1</td>
					<td><input type="text" readonly="readonly" id="fourthchange"/></td>
					<td><input type="text" readonly="readonly" id="fourthFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="fourth60"/></td>
					<td><input type="text" readonly="readonly" id="fourth80"/></td>
				</tr>
				<tr>
				  <td>Fifth Gear</td>
					<td><input type="text" id="fifthgear" />:1</td>
					<td><input type="text" readonly="readonly" id="fifthchange"/></td>
					<td><input type="text" readonly="readonly" id="fifthFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="fifth60"/></td>
					<td><input type="text" readonly="readonly" id="fifth80"/></td>
				</tr>
				<tr>
				  <td>Sixth Gear</td>
					<td><input type="text" id="sixthgear" />:1</td>
					<td><input type="text" readonly="readonly" id="sixthchange"/></td>
					<td><input type="text" readonly="readonly" id="sixthFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="sixth60"/></td>
					<td><input type="text" readonly="readonly" id="sixth80"/></td>
				</tr>
			</table>
		</form>	
</body>
</html>
Click to expand...

wow, that will be a handy program. I hope the admins grab it and put it on top with a sticky.
 
SuperBuickGuy said:
pancake said:
I was really bored.. had some extra rum.. so I wrote up this short code for calculating speed @ different RPM's based on the different final drives and transmissions.. though I conveniently left out the 5 speeds. I'll eventually turn this into PHP so it can be hosted. But.. if you're so inclined.. copy and paste it into a txt file with the extension .xml and your web browser will run it.

I wish I did this all the time.. I'm not very good at it.

HTML: 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
	  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>

    <title>Gearing, RPM, and Vehicle Speed Calculator</title>
		<script>
    	function calculate()
				{
				 	var first = parseFloat(document.getElementById("firstgear").value);
					var second = parseFloat(document.getElementById("secondgear").value);
					var third = parseFloat(document.getElementById("thirdgear").value);
					var fourth = parseFloat(document.getElementById("fourthgear").value);
					var fifth = parseFloat(document.getElementById("fifthgear").value);
					var sixth = parseFloat(document.getElementById("sixthgear").value);
					var wheel = parseInt(document.getElementById("wheeldiameter").value);
					var rpm = parseInt(document.getElementById("maxrpm").value);
					var diffy = parseFloat(document.getElementById("diff").value);
										
					document.getElementById("firstFinalRatio").value = finalRatio(diffy, first).toFixed(2);
					document.getElementById("first60").value = maxRpm(60, diffy, first, wheel).toFixed(2);
					document.getElementById("first80").value = maxRpm(80, diffy, first, wheel).toFixed(2);	
					
					document.getElementById("secondchange").value = percentChange(first, second) * 100;	
					document.getElementById("secondFinalRatio").value = finalRatio(diffy, second).toFixed(2);
					document.getElementById("second60").value = maxRpm(60, diffy, second, wheel).toFixed(2);
					document.getElementById("second80").value = maxRpm(80, diffy, second, wheel).toFixed(2);	  
					
					document.getElementById("thirdchange").value = percentChange(second, third) * 100;
					document.getElementById("thirdFinalRatio").value = finalRatio(diffy, third).toFixed(2);
					document.getElementById("third60").value = maxRpm(60, diffy, third, wheel).toFixed(2);
					document.getElementById("third80").value = maxRpm(80, diffy, third, wheel).toFixed(2);
					
				  document.getElementById("fourthchange").value = percentChange(third, fourth) * 100;
					document.getElementById("fourthFinalRatio").value = finalRatio(diffy, fourth).toFixed(2);
					document.getElementById("fourth60").value = maxRpm(60, diffy, fourth, wheel).toFixed(2);
					document.getElementById("fourth80").value = maxRpm(80, diffy, fourth, wheel).toFixed(2);
						
					document.getElementById("fifthchange").value = percent = percentChange(fourth, fifth) * 100;
					document.getElementById("fifthFinalRatio").value = finalRatio(diffy, fifth).toFixed(2);
					document.getElementById("fifth60").value = maxRpm(60, diffy, fifth, wheel).toFixed(2);
					document.getElementById("fifth80").value = maxRpm(80, diffy, fifth, wheel).toFixed(2);	
					
					document.getElementById("sixthchange").value = percentChange(fifth, sixth) * 100;
					document.getElementById("sixthFinalRatio").value = finalRatio(diffy, sixth).toFixed(2);
					document.getElementById("sixth60").value = maxRpm(60, diffy, sixth, wheel).toFixed(2);
					document.getElementById("sixth80").value = maxRpm(80, diffy, sixth, wheel).toFixed(2);	
				}//end function calculate
				
				function maxRpm(speed, diff, gear, wheel)
				{
				  return ((diff * gear) * speed * 336)/wheel;
				}//end function rpmAt60
				
				function finalRatio(diff, gear)
				{
				  return diff * gear;
				}//end finalRatio
				
				function wheelDistance(wheelDiameter)
				{
				  return (wheelDiameter/12) * 3.14159;
				}//end function wheelDistance
				
				function percentChange(ratio1, ratio2)
				{
				  return (ratio1 - ratio2) / ratio1;
				}//end function percentChange
				
				function getRatio()
				{	//Transmissions and ratios
					var ratios = [ [0, 0, 0, 0, 0, 0], 
					             [2.85, 2.02, 1.35, 1.00, 0, 0],      
				               [2.52, 1.88, 1.47, 1.00, 0, 0],      
											 [2.20, 1.64, 1.27, 1.00, 0, 0],      
											 [2.43, 1.61, 1.23, 1.00, 0, 0],      
											 [2.66, 1.78, 1.30, 1.00, .74, .50],  
											 [3.28, 2.13, 1.57, 1.23, 1.00, .76], 
											 [0, 0, 0, 0, 0, 0] ];										 	
					 
					 var trans = parseFloat(document.getElementById("transmission").value);
					
					  document.getElementById("firstgear").value = ratios[trans][0].toFixed(2);
					  document.getElementById("secondgear").value = ratios[trans][1].toFixed(2);
					  document.getElementById("thirdgear").value = ratios[trans][2].toFixed(2);
					  document.getElementById("fourthgear").value = ratios[trans][3].toFixed(2);
					  document.getElementById("fifthgear").value = ratios[trans][4].toFixed(2);
					  document.getElementById("sixthgear").value = ratios[trans][5].toFixed(2);

				}//end function getRatios
    </script>

  </head>
  <body>
	  <form>
		  <table border = "1">
			  <tr>
				  <th colspan="6">Vehicle Data</th>
				</tr>
				<tr>
				  <td>Wheel Diameter: </td>
					<td><input type="text" id="wheeldiameter" /></td>
					<td>Max RPM: </td>
					<td><input type="text" id="maxrpm" /></td>
					<td><input colspan="2" type="submit" onclick="calculate()" value="Calculate"/></td>
				</tr>
				<tr>
					<td>Differential Ratio:</td>
					<td><input type="text" id="diff" /></td>
				  <td>Transmission:</td>
					<td><select id="transmission" onchange="getRatio()">
							  <option value="0"></option>
							  <option value="1">Saginaw 4 Speed</option>
							  <option value="2">Muncie M20</option>
							  <option value="3">Muncie M21 or M22</option>
							  <option value="4">Borg Warner Super T10</option>
							  <option value="5">1994+ T56</option>
							  <option value="6">Richmond ROD</option>
							  <option value="7">Custom Ratios</option>
							</select>
							</td>
				</tr>
				<tr>
				  <td colspan="2"><b>Gear Ratios</b></td>		
				  <td><b>% Change</b></td>
					<td><b>Final Ratio</b></td>
					<td><b>RPM @ 60 MPH</b></td>
					<td><b>RPM @ 80 MPH</b></td>
				</tr>	
				<tr>
				  <td>First Gear</td>
					<td><input type="text" id="firstgear" />:1</td>
					<td></td>
					<td><input type="text" readonly="readonly" id="firstFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="first60"/></td>
					<td><input type="text" readonly="readonly" id="first80"/></td>
				</tr>
				<tr>
				  <td>Second Gear</td>
					<td><input type="text" id="secondgear" />:1</td>
				  <td><input type="text" readonly="readonly" id="secondchange"/></td>
					<td><input type="text" readonly="readonly" id="secondFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="second60"/></td>
					<td><input type="text" readonly="readonly" id="second80"/></td>
				</tr>
				<tr>
				  <td>Third Gear</td>
					<td><input type="text" id="thirdgear" />:1</td>
					<td><input type="text" readonly="readonly" id="thirdchange"/></td>
					<td><input type="text" readonly="readonly" id="thirdFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="third60"/></td>
					<td><input type="text" readonly="readonly" id="third80"/></td>
				</tr>
				<tr>
				  <td>Fourth Gear</td>
					<td><input type="text" id="fourthgear" />:1</td>
					<td><input type="text" readonly="readonly" id="fourthchange"/></td>
					<td><input type="text" readonly="readonly" id="fourthFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="fourth60"/></td>
					<td><input type="text" readonly="readonly" id="fourth80"/></td>
				</tr>
				<tr>
				  <td>Fifth Gear</td>
					<td><input type="text" id="fifthgear" />:1</td>
					<td><input type="text" readonly="readonly" id="fifthchange"/></td>
					<td><input type="text" readonly="readonly" id="fifthFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="fifth60"/></td>
					<td><input type="text" readonly="readonly" id="fifth80"/></td>
				</tr>
				<tr>
				  <td>Sixth Gear</td>
					<td><input type="text" id="sixthgear" />:1</td>
					<td><input type="text" readonly="readonly" id="sixthchange"/></td>
					<td><input type="text" readonly="readonly" id="sixthFinalRatio"/></td>
					<td><input type="text" readonly="readonly" id="sixth60"/></td>
					<td><input type="text" readonly="readonly" id="sixth80"/></td>
				</tr>
			</table>
		</form>	
</body>
</html>
Click to expand...

wow, that will be a handy program. I hope the admins grab it and put it on top with a sticky.
Click to expand...

That is a pretty rough sketch.. no validation in it. I'm working on a better version of it right now. I have it available in an excel spreadsheet if you want it... just PM me and I'll send it over.
 
I make only one comment from my experiences with these tire size/ratio calculations, that being some years ago I went by tire size, rear ratio and final drive which for me was .70 overdrive being it was a 200 4r trans....

now I had the correct gear count in there for the speedo, supposedly....

I found out my tach was dead accurate up to 2500 rpm, after that it gained about 5-600 rpm, I proved that with a digital audio oscillator driving a large transistor, and firing the tach terminal on the HEI, looking at the results with my Tektronics scope....using 60 hz line freq for comparisons to keep everything honest......

and SO, I eventually bought a Garmin GPS to see about some speeds I had supposedly accomplished, turns out my speedometer was over indicating by better than 15%, yet at even 80 mph the tach reads 2500 rpm, which is where it's accurate....

I changed driven gear for the speedo, and so got it reading dead nutz on at all speeds, up to 80 mph, which is really only 78 mph via GARMIN.....now here it got interesting, I ran up to 100 indicated and it was really only doing 94mph......via GARMIN, I ran outta room in traffic so ended the test.....

DO NOT believe your supposed instrumentation in these old sharks......

for one thing even the cheep aftermarket engine water temp gauge reads 10F high proven with two different gauges....

NOW< I have no clue as to how/why those tire speed rpm calculators are that far off.....just I know my shit is NOW correct up to 80 mph....

:suicide:
 
mrvette said:
I make only one comment from my experiences with these tire size/ratio calculations, that being some years ago I went by tire size, rear ratio and final drive which for me was .70 overdrive being it was a 200 4r trans....

now I had the correct gear count in there for the speedo, supposedly....

I found out my tach was dead accurate up to 2500 rpm, after that it gained about 5-600 rpm, I proved that with a digital audio oscillator driving a large transistor, and firing the tach terminal on the HEI, looking at the results with my Tektronics scope....using 60 hz line freq for comparisons to keep everything honest......

and SO, I eventually bought a Garmin GPS to see about some speeds I had supposedly accomplished, turns out my speedometer was over indicating by better than 15%, yet at even 80 mph the tach reads 2500 rpm, which is where it's accurate....

I changed driven gear for the speedo, and so got it reading dead nutz on at all speeds, up to 80 mph, which is really only 78 mph via GARMIN.....now here it got interesting, I ran up to 100 indicated and it was really only doing 94mph......via GARMIN, I ran outta room in traffic so ended the test.....

DO NOT believe your supposed instrumentation in these old sharks......

for one thing even the cheep aftermarket engine water temp gauge reads 10F high proven with two different gauges....

NOW< I have no clue as to how/why those tire speed rpm calculators are that far off.....just I know my shit is NOW correct up to 80 mph....

:suicide:
Click to expand...

I'm not using the vette gauges to determine rpm @ a particular speed. The formula for estimating your engine RPM at a particular speed is:

(Final Drive * MPH * 336)/Tire Diameter in inches

Where 336 is a constant..

So ((3.36 * 1.00) * 60 * 336)/27 = 2508.08

Where 3.36 is the rear end ratio, 1.00 is the 4th gear ratio, 60 mph is the desired speed, and 27 inches is the tire diameter.
 
pancake said:
mrvette said:
I make only one comment from my experiences with these tire size/ratio calculations, that being some years ago I went by tire size, rear ratio and final drive which for me was .70 overdrive being it was a 200 4r trans....

now I had the correct gear count in there for the speedo, supposedly....

I found out my tach was dead accurate up to 2500 rpm, after that it gained about 5-600 rpm, I proved that with a digital audio oscillator driving a large transistor, and firing the tach terminal on the HEI, looking at the results with my Tektronics scope....using 60 hz line freq for comparisons to keep everything honest......

and SO, I eventually bought a Garmin GPS to see about some speeds I had supposedly accomplished, turns out my speedometer was over indicating by better than 15%, yet at even 80 mph the tach reads 2500 rpm, which is where it's accurate....

I changed driven gear for the speedo, and so got it reading dead nutz on at all speeds, up to 80 mph, which is really only 78 mph via GARMIN.....now here it got interesting, I ran up to 100 indicated and it was really only doing 94mph......via GARMIN, I ran outta room in traffic so ended the test.....

DO NOT believe your supposed instrumentation in these old sharks......

for one thing even the cheep aftermarket engine water temp gauge reads 10F high proven with two different gauges....

NOW< I have no clue as to how/why those tire speed rpm calculators are that far off.....just I know my shit is NOW correct up to 80 mph....

:suicide:
Click to expand...

I'm not using the vette gauges to determine rpm @ a particular speed. The formula for estimating your engine RPM at a particular speed is:

(Final Drive * MPH * 336)/Tire Diameter in inches

Where 336 is a constant..

So ((3.36 * 1.00) * 60 * 336)/27 = 2508.08

Where 3.36 is the rear end ratio, 1.00 is the 4th gear ratio, 60 mph is the desired speed, and 27 inches is the tire diameter.
Click to expand...

Check it with a GPS when done....

:bestwishes:
 
mrvette said:
pancake said:
mrvette said:
I make only one comment from my experiences with these tire size/ratio calculations, that being some years ago I went by tire size, rear ratio and final drive which for me was .70 overdrive being it was a 200 4r trans....

now I had the correct gear count in there for the speedo, supposedly....

I found out my tach was dead accurate up to 2500 rpm, after that it gained about 5-600 rpm, I proved that with a digital audio oscillator driving a large transistor, and firing the tach terminal on the HEI, looking at the results with my Tektronics scope....using 60 hz line freq for comparisons to keep everything honest......

and SO, I eventually bought a Garmin GPS to see about some speeds I had supposedly accomplished, turns out my speedometer was over indicating by better than 15%, yet at even 80 mph the tach reads 2500 rpm, which is where it's accurate....

I changed driven gear for the speedo, and so got it reading dead nutz on at all speeds, up to 80 mph, which is really only 78 mph via GARMIN.....now here it got interesting, I ran up to 100 indicated and it was really only doing 94mph......via GARMIN, I ran outta room in traffic so ended the test.....

DO NOT believe your supposed instrumentation in these old sharks......

for one thing even the cheep aftermarket engine water temp gauge reads 10F high proven with two different gauges....

NOW< I have no clue as to how/why those tire speed rpm calculators are that far off.....just I know my shit is NOW correct up to 80 mph....

:suicide:
Click to expand...

I'm not using the vette gauges to determine rpm @ a particular speed. The formula for estimating your engine RPM at a particular speed is:

(Final Drive * MPH * 336)/Tire Diameter in inches

Where 336 is a constant..

So ((3.36 * 1.00) * 60 * 336)/27 = 2508.08

Where 3.36 is the rear end ratio, 1.00 is the 4th gear ratio, 60 mph is the desired speed, and 27 inches is the tire diameter.
Click to expand...

Check it with a GPS when done....

:bestwishes:
Click to expand...

Oh.. I forgot. You invented arithmetic, too.

It's a straight forward calc.. (final drive * mph * 336)/tire diameter.. ofcourse it doesn't take into account tire growth at speed... but the rest is rpm and gear ratio. It'll be close enough for government work.
 
Last edited:
Hey, when comparing gas mileage like the 25 highway mpg I used to get with my Z28 or the 26 highway MPG I get with my LS2 .... ..... I also get 25mpg with my 2.3L (140ci) 4 banger Mustang so I get the same MPG in a 400HP V8 and a 105 HP 4 banger ... LOL ... must be the driver ....LOL
 
pancake said:
I finally took the time to finish the DOM script and put up the little gearing calculator.
Let me know if you want any data added. I have a few ideas to expand the table that i will be adding.

Http://78ael48.com/gearing
Click to expand...

Yup typed in 'wheel diameter'.....should be TIRE diameter, but when dealing with those sites using that, I went to others that used the tire SIZE, like at Tire rack, I ASSumed the fact that it would allow for the decreased effective circumference of the tire because of weight of car on the ground, SO, how much to allow for that weight causing an effective smaller diameter and slower speeds than you think....??

then to the other point, the lack of accuracy in stock shark speedo and tach....

Turtlevette and I went around about this shit some years ago, and so I got a line on a GPS for like 120 bux at the time, and figgered it's good for some planned road trips, so bought it.....

and it shoved reality up my ASS but good on my supposed calculators and also my tach accuracy was WAY the fuck off....after 2500 rpm.... it's a stock '75-77 electronic tach, with proper filter and dead nutz on till 2500 rpm, :shocking:
 
mrvette said:
pancake said:
I finally took the time to finish the DOM script and put up the little gearing calculator.
Let me know if you want any data added. I have a few ideas to expand the table that i will be adding.

Http://78ael48.com/gearing
Click to expand...

Yup typed in 'wheel diameter'.....should be TIRE diameter, but when dealing with those sites using that, I went to others that used the tire SIZE, like at Tire rack, I ASSumed the fact that it would allow for the decreased effective circumference of the tire because of weight of car on the ground, SO, how much to allow for that weight causing an effective smaller diameter and slower speeds than you think....??

then to the other point, the lack of accuracy in stock shark speedo and tach....

Turtlevette and I went around about this shit some years ago, and so I got a line on a GPS for like 120 bux at the time, and figgered it's good for some planned road trips, so bought it.....

and it shoved reality up my ASS but good on my supposed calculators and also my tach accuracy was WAY the fuck off....after 2500 rpm.... it's a stock '75-77 electronic tach, with proper filter and dead nutz on till 2500 rpm, :shocking:
Click to expand...

let me get this straight, you trust the government rather then your abilities? :amazed: After all, the government owns GPS system :thumbs:
 
SuperBuickGuy said:
mrvette said:
pancake said:
I finally took the time to finish the DOM script and put up the little gearing calculator.
Let me know if you want any data added. I have a few ideas to expand the table that i will be adding.

Http://78ael48.com/gearing
Click to expand...

Yup typed in 'wheel diameter'.....should be TIRE diameter, but when dealing with those sites using that, I went to others that used the tire SIZE, like at Tire rack, I ASSumed the fact that it would allow for the decreased effective circumference of the tire because of weight of car on the ground, SO, how much to allow for that weight causing an effective smaller diameter and slower speeds than you think....??

then to the other point, the lack of accuracy in stock shark speedo and tach....

Turtlevette and I went around about this shit some years ago, and so I got a line on a GPS for like 120 bux at the time, and figgered it's good for some planned road trips, so bought it.....

and it shoved reality up my ASS but good on my supposed calculators and also my tach accuracy was WAY the fuck off....after 2500 rpm.... it's a stock '75-77 electronic tach, with proper filter and dead nutz on till 2500 rpm, :shocking:
Click to expand...

let me get this straight, you trust the government rather then your abilities? :amazed: After all, the government owns GPS system :thumbs:
Click to expand...

GPS is a digital system, if it lies to ME, it lies to everyone for every purpose and therefore is totally useless.....I can't see the point of your comment, other than to cause a smirk....

So, OK, smirk.....:bump:
 
I added a tire diameter calculator to the page. Remember that this is just for estimating.. it's in the ball park, though.

Once again.. This calculator doesn't have a damned thing to do with the inaccuracies of the factory gauges. It calculates speed by considering engine RPM, tire rpm, and tire circumference. I realize that tires are not perfect circles and there are many variables to take into account like vehicle weight, inflation, growth, etc.... but your typical consumer tire likely doesn't grow 2 inches unless you've hit warp drive and are moving into a new galaxy. The miniscule growth is not going to skew the numbers enough to invalidate the numbers.

I just did some checking on bias ply min growth slicks for drag racing. Hoosiers will grow about 1.5" at 60 degrees F and 3" at 100 degrees and 5" at 100 degrees and 180 mph. A typical passenger tire isn't going to see anything near that.

And this gearing calculator is digital. What if it lies to you?
 
Last edited:
mrvette said:
SuperBuickGuy said:
mrvette said:
pancake said:
I finally took the time to finish the DOM script and put up the little gearing calculator.
Let me know if you want any data added. I have a few ideas to expand the table that i will be adding.

Http://78ael48.com/gearing
Click to expand...

Yup typed in 'wheel diameter'.....should be TIRE diameter, but when dealing with those sites using that, I went to others that used the tire SIZE, like at Tire rack, I ASSumed the fact that it would allow for the decreased effective circumference of the tire because of weight of car on the ground, SO, how much to allow for that weight causing an effective smaller diameter and slower speeds than you think....??

then to the other point, the lack of accuracy in stock shark speedo and tach....

Turtlevette and I went around about this shit some years ago, and so I got a line on a GPS for like 120 bux at the time, and figgered it's good for some planned road trips, so bought it.....

and it shoved reality up my ASS but good on my supposed calculators and also my tach accuracy was WAY the fuck off....after 2500 rpm.... it's a stock '75-77 electronic tach, with proper filter and dead nutz on till 2500 rpm, :shocking:
Click to expand...

let me get this straight, you trust the government rather then your abilities? :amazed: After all, the government owns GPS system :thumbs:
Click to expand...

GPS is a digital system, if it lies to ME, it lies to everyone for every purpose and therefore is totally useless.....I can't see the point of your comment, other than to cause a smirk....

So, OK, smirk.....:bump:
Click to expand...

done, and done :amused::bump:
 
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