Ring and pinion strength

[clutchdust]

Just thinking of something and looking for some input.
Given two cars with the exact same final drive, does a rear end with lower gears (numerically higher) have greater, lesser or no difference in strength than one with higher gears?

 

[pcf_mark]

I look forward to others chiming in. The lower numbers like 3.36:1 have fewer teeth on the pinion in the same physical space so they should be larger and meatier. My experience with destroying these is that the diff case itself fails before the ring and pinion. Then a few ring gear teeth shear off is the next failure.

I think the pinion bends under load between the bearings (effectively shortening it) and the contact area between the pinion and ring gear teeth changes to something it was not designed for and rind gear teeth fail.

I have only seen one example where the pinion was sheared off.

 

[DeeVeeEight]

I only trashed one and I guess I was the exception. It was a 3:73 rear and I launched too hard and shifted too hard. - I turned the gears into salad but the case held up fine.

 

[DWncchs]

I would think the higher the gear the less stress the rear end would be under.
edit- to clarify , higher meaning higher in number like 4:56

 

[68/70Vette]

I've really wondered about this also. I have a Richmond 5 speed that I'm planning on installing in my 70. The 70 will have a 3.08:1 rear end. The Richmond is 1:1 in fifth gear. In first gear, the ratios with the Richmond are the effectively the same as a Muncie 4 speed driving a 4.11:1. A 4.11:1 is really great for first gear! But is a 3.08:1 creating a problem for an engine with a lot of horsepower.

I think this would be a good question for Tom of Toms Differentials. I plan to order a 3.08:1 ring and pinion from him and when I do, I'll ask him this question. An alternate is to buy a Tremac transmission with an overdrive 5th or 6th gear and have a 3.73:1 differential. Since I have the Richmond, I'm not too inclined to go the Tremac route.

 

[clutchdust]

That's exactly the reason I'm curious. I already have the Richmond and a set of 3.07s. The original diff had 2.92s and I actually think I would prefer that gear with this tranny but before I go through the hassle, I just want to know if jumping on it is going to cost me lots of metal and cash first.

 

[DeeVeeEight]

I've really wondered about this also. I have a Richmond 5 speed that I'm planning on installing in my 70. The 70 will have a 3.08:1 rear end. The Richmond is 1:1 in fifth gear. In first gear, the ratios with the Richmond are the effectively the same as a Muncie 4 speed driving a 4.11:1. A 4.11:1 is really great for first gear! But is a 3.08:1 creating a problem for an engine with a lot of horsepower.

I think this would be a good question for Tom of Toms Differentials. I plan to order a 3.08:1 ring and pinion from him and when I do, I'll ask him this question. An alternate is to buy a Tremac transmission with an overdrive 5th or 6th gear and have a 3.73:1 differential. Since I have the Richmond, I'm not too inclined to go the Tremac route.

I had a Richmond 5 speed (1:1 5th gear) too. With the 3:73's the gears were too low for any kind of street driving, I was constantly rowing through the gears just to get up to 35 mph. First gear was almost too low to be any good. When I trashed the rear and had it rebuilt I had 3:25's installed, the gear spread was much more friendly, however I was unhappy with 3000 rpm at 70 mph so I switched out the Richmond for a TKO 5 speed with an .82 overdrive, now 70 mph is a much more comfortable 2000 rpm. Performance off the line is not too bad either - at least for a 400 hp daily driver. If all you want is track time then I would stay with the higher ratios but I think that you will be OK with the 3:08's, my only concern would be your OD ratio being too tall.
I hope that helps!

 

[DeeVeeEight]

That's exactly the reason I'm curious. I already have the Richmond and a set of 3.07s. The original diff had 2.92s and I actually think I would prefer that gear with this tranny but before I go through the hassle, I just want to know if jumping on it is going to cost me lots of metal and cash first.

In my experience YES. I have learned that it is prudent to slip the clutch off the line and not crunch the gears too hard. The Richmond will hold up fine but something aft of it will probably let go.

 

[Carb Doc]

I think that you have the best possible setup with the richmond and 3.08, this would allow you to run 70mph at 2800rpm with a tire 26" tall, if you have lots of low rpm torque this would be good, if not you may want to run 3.23 or 3.36 to allow the motor to pull up harder in 5th, 3.55 is a real good set up with the richmond if you can turn the motor up into the higher rpm range, will be very strong in 5th as well, will run 70 mph at 3200 rpm and 152 mph at 7000. Depends on how strong your motor is and weather or not you are able to run higher rpm with out putting the rods into the oil pan.

 

[Carb Doc]

The more teeth possible on the pinion, for any given ratio, the stronger the gear set will be.

 

[mrvette]

The more teeth possible on the pinion, for any given ratio, the stronger the gear set will be.

That's what I think too.....

years ago I blew out a 2.94 mild rear in my work truck, it was just a 8.25" Mopar rear, got a buddie's old tow car, went with the large POSI 9.25 Auburn style diffy in it....3.21 ratio.....for a gear change of only 10%, that stupid truck went from a total slug off line into a freeking hotrod that would embarrass a lot of 'quick' cars....not too awful evil on the freeways either wit that lockup converter, 3 speed 999 auto tranny....stupid truck has 300k miles on it, OEM engine and still runs fine....

I thinking of a 308 for the vette, over my 336 in there, needs a pinion seal anyway, so WTF, maybe just do the whole thing....

 

[pcf_mark]

More teeth on the pinion will make every tooth smaller and head of the pinion smaller also to allow for engagement. The head of the pinion has the be the same O.D. regardless of ratio to fit in the case. I have a 4.11 and a 3.36 around I'll try to dig them up and shoot some photos.

I have a t56 and 4.11s and it is a hoot to drive with 26" tires. I think I am at 2,200 at 60-65 mph. First is a little short but is great for getting the car moving with my big cam and ported heads.

 

[GTR1999]

For vettes there are only 4 mfg,that I know for C2 & C3 gears. US Gear(toms),Richmonds,Yukon (randys imported) and Motive(never used).

The cut with these is supposed to be slightly different then GM made but I can't say. All parts can and will fail from stock 10-bolts to 12-bolts,given enough abuse and power thrown at them in a car that hooks up.

Drag gears are softer but are not for street use. I'm now waiting on a set of 390 Richmonds that are being cold stabilized to come in for a build.

I haven't had any failures with gears even when posi cases blew apart. That doesn't mean they can't break.

Usually more teeth adds to the strength. For example I'll use a 373 over a 370everyday of the week. The 370 is a 37/10 tooth set, the 373 is 41/11.

Differential failure usually results from abuse or poor assembly techniques as witnessed by the picture of that C2 diff that came apart not only 1 but 2 by that same builder. Ring gear bolt backout,cracked posi cases,and worn cross shaft holes also make up the common list for breakage.

I see a lot of home diff setup where the patterns is just way out and left. I can only guess the rebuilder got tired of the constant break down, shim change, lash change and testing to dial them in.

 

[pcf_mark]

The tooth ratio makes a lot sense - more teeth even if smaller, are engaged at once and trying to transmit the power.

I would like to know if the cold stabilizing yields any improvement in unit life. I was thinking the factory posi case, deburred, shot peened and cold stabilized might last a while longer than stock.