Rear Diff Cooler

phantomjock

phantomjock

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Retired Again!
Well, AS long as I'm, at it... (C-3/'78 major mod)

I looked at my newly rebuilt 4.11 (VanSteel and Toms) and the parts to assemble the rear suspension, and thought - well, isn't this the time to add a rear diff cooler. DOOH - shoulda added that to my list earlier! :suicide:
Yep do it now and avoiid a rebuild/mod later.

So, I have a few questiond guys:
1. Can I use the "drain" plug for one of the lines? - Like the feed line to the pump and cooler?
2. Where in the rear cover should the return line go? Above the midway point?
3. Temp in the case - low point I suppose.
4. Electric pump on a thermostat/relay like radiators?
5. How big a pump GPH - any recommendations?
6. How big a cooler? 13 row/15 row?
7. FAN? CFM recommendations (A puller? Shroud?)
8. Thinking at least AN-8 or maybe -10 - ideas?


Any help or advice on any of these is MUCH appreciated!

Thanks, and
Cheers - Jim

FWIW - NO SPARE since 1981! Double mount rear 'glass Spring, electric fuel pomp/surge tank and filter all complicate the mounting. Considering Boom Tubes not rear exhaust.
 
I have only ONE comment, that being about MY Muncie running cooler and much easier to shift from doing 30 W synthetic engine oil.....maybe 15? years ago for a few years....

now, I have heard that the same oil with GM additives will run much cooler, as was with my Muncie...not so much energy spent whipping heavy oils around ....

NOW, combined with that in FWD vehicles, they seem to take the diffy lube into the same as the ATF now that's still a standard diffy, and so why NOT, what is the difference between front and rear drive on the ring/pinion/spider/side gears???

about POSI, I dunno....but they say friction additives are in ATF...

well, isn't that waht the GM posi additive is all about???

:twitch::smash:
 
redvetracr said:
have you priced a pump capable of moving gear lube?
Click to expand...

Dunno what you mean, but I am tempted to run a street test using 30W engine oil and posi additive in my diffy, fore shits and giggles....

trick is, I don't race, just drive quickly in FLORIDA traffic....

thing is, I not prepared to take a science ANALysis of wear on the unit for the test....

but I BET I could do ATF back there and be fine....

:smash::smash::twitch:
 
mrvette said:
redvetracr said:
have you priced a pump capable of moving gear lube?
Click to expand...

Dunno what you mean, but I am tempted to run a street test using 30W engine oil and posi additive in my diffy, fore shits and giggles....

trick is, I don't race, just drive quickly in FLORIDA traffic....

thing is, I not prepared to take a science ANALysis of wear on the unit for the test....

but I BET I could do ATF back there and be fine....

:smash::smash::twitch:
Click to expand...

Don't do it. The old Jags used engine oil in the stick trannys. Burned em up. They use 90W on the rebuilds.
The old Chevy constant 4wd used ATF. Burned em up.
 
big2bird said:
turtlevette said:
redvetracr said:
have you priced a pump capable of moving gear lube?
Click to expand...

use a fuel pump. 40 bucks
Click to expand...

"I don't think so Tim."
Click to expand...

I could respect your answer a lot more if you gave me a technical reason other than it says "gas" and not "oil" on the label. Remember it doesn't have to pressurize anything, just move the oil slowly say a few quarts or a gallon a minute. That would be enough to exchange all the oil in the diff in a minute. Consider that nobody on this forum will ever get a diff hot enough to require cooling anyway. It's just a cool looking mod.

I kinda like what Roger is doing over on CF. Mythbusting.
 
A fuel pump stays running cool from the fuel, now try to run hot oil through it that is much thicker too. I think it won't last or even work. A mocal oil pump or a mech driven single stage scavenge section pump will work reliably. Add a filter and you will need to overcome a restriction. We have a cooler setup w/ gauge and thermo switched pump on the 77. When blasting down the autobahn it does kick in.

As for setup, you need to pull it from somewhere down the fluid level do you have to drill & tap the lid.

548d28337d9ec9.jpg

Sent from my GT-I9000 using Tapatalk
 
Thanks - Great Help

TT -
That's the ticket. :thumbs:
Looks like AN-8 lines on about 1/2inch in/out on the pump. And unless I miss-counted - about a 15 row cooler too. I don't see any fans - just the Ram Air Shroud. BUT the additional fitting left of the lower sump line? Drain at lowest point? Good plan!

VERY HELPFUL picture.

But, now compromises and adjustments - the crossmembers - fuel pump and filter on the forward - and surge tank on the one below the fuel tank.
Ahh - sweet adjustments!

Thanks guys -
Cheers - Jim
 
when i was a dumb kid i was at a road race event where a well known canadian driver (allan moffat) had an unusual setup under his ford in that he was using another shocky as the pump to move the diff oil through a cooler.I thought it was very clever in that the harder they cornered or the roughfer the track the more it pumped. just a thought,no wires,simple,compact.
 
turtlevette said:
big2bird said:
turtlevette said:
redvetracr said:
have you priced a pump capable of moving gear lube?
Click to expand...

use a fuel pump. 40 bucks
Click to expand...

"I don't think so Tim."
Click to expand...
Remember it doesn't have to pressurize anything, just move the oil slowly say a few quarts or a gallon a minute. That would be enough to exchange all the oil in the diff in a minute. Consider that nobody on this forum will ever get a diff hot enough to require cooling anyway.
Click to expand...

Then why not just tap the top inline with the ring gear, install a slim cooler behind it, even with the top and bottom, and run the return to the drain plug. Let the splash of the ring gear pump it out, with gravity return.
Model T's do this, and when the line breaks, the 4 qts are gone in seconds.
No special added pump required.
 
shipy59 said:
when i was a dumb kid i was at a road race event where a well known canadian driver (allan moffat) had an unusual setup under his ford in that he was using another shocky as the pump to move the diff oil through a cooler.I thought it was very clever in that the harder they cornered or the roughfer the track the more it pumped. just a thought,no wires,simple,compact.
Click to expand...

Yes, a stewart shock pump, I have a couple of those and will use them in one of my current projects just to see how it goes.

Phantom,

The setup uses brake cooling hose to supply cold under car air to the cooler:

24e4128c37e107.jpg
 
shipy59 said:
when i was a dumb kid i was at a road race event where a well known canadian driver (allan moffat) had an unusual setup under his ford in that he was using another shocky as the pump to move the diff oil through a cooler.I thought it was very clever in that the harder they cornered or the roughfer the track the more it pumped. just a thought,no wires,simple,compact.
Click to expand...

I like that idea. I've been kicking around trying to come up with a setup that doesn't require a pump. My diff case has a drain plug on the bottom (in addition to the fill plug in the batwing), and I've been trying to figure out a system with a cooler/extra sump and a check valve/ball in one of the lines to allow accel/decel forces to pump the oil into and out of the cooler. I'm still working out the bugs on it.
Right now I'm just relying on the limited track session lengths (generally 20 minutes) and the aluminum batwing construction to conduct out heat better than the original cast iron and steel setup.
 
69427 said:
I like that idea. I've been kicking around trying to come up with a setup that doesn't require a pump. My diff case has a drain plug on the bottom (in addition to the fill plug in the batwing), and I've been trying to figure out a system with a cooler/extra sump and a check valve/ball in one of the lines to allow accel/decel forces to pump the oil into and out of the cooler.
Click to expand...

See post #12. I tell you Mike, the force of the ring gear flinging the oil around would be enough. Just imagine driving around with the filler plug gone.:twitch:
 
Twin_Turbo said:
A fuel pump stays running cool from the fuel, now try to run hot oil through it that is much thicker too. I think it won't last or even work. A mocal oil pump or a mech driven single stage scavenge section pump will work reliably. Add a filter and you will need to overcome a restriction. We have a cooler setup w/ gauge and thermo switched pump on the 77. When blasting down the autobahn it does kick in.

As for setup, you need to pull it from somewhere down the fluid level do you have to drill & tap the lid.
Click to expand...

I looked up your mocal pump. I agree there is no need to take a chance using a fuel pump if the mocal is only $180. I might experiment though.

What temp is your t-stat set at and how fast and long did you have to drive to kick it in?

My 456 spins at 5000 on the highway on long trips and it smells hot when i stop.

I wonder if you should put a filter on the suction side of that pump. Mine always has a LOT of metal in it sitting in the bottom and you are sucking the oil right off the floor.
 
Last edited:
The filter is on the pressure side, otherwise the pump won't be able to pump the fluid. Just a mesh prefilter before the pump so no trash goes through and a magnet near the pickup in the cover

Sent from my GT-I9000 using Tapatalk
 
REAR END Oil Pressure -- What is it?

Got a bunch of work done on the rear cover this weekend.
Got the pickup and returns all drilled and tapped and the temp switch for the pump and a temp sensor for a gauge monitor.

As I was reassembling - mounting the the rear cover to the diff, I got to thinking, If I knew what the approximate pressure of the diff fluid is supposed to be - I could do a "leakdown check" before I remount to the carrier and continue on with the 6link assembly.

Naturally if I mount it all up - and continue with the build - and it leaks -- re dissamble and reseal -- ARGHH! [I suppose the vent will leak some pressure too - but can't I bypass that - finger/tape?]

So the Question of the Hour is:
"What is the oil pressure (aproximately) in the differential?"
 
Last edited:
Pressure? Aren't you just looking for flow? The vent is to keep from blowing past the seals.
 
the older Chevy power books have a small section on cooling a Corvette diff, the GM engineers recommend you drill the rear cover in two places behind the ring gear.
 
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