: got a new rear and an Idea how to save it!



c5racr1
02-09-05, 04:50 PM
Just got my new centersection installed and I think I am going to install a diff cooler and a pump on it. It is common knowledge that cars with low gearing , such as 3.73 tend to run a MUCH higher diff fluid temp than cars with lower gearing -3.15. I am thinking that due to the very small center section and the lack of cooling fins and the lack of large amounts of air to release the heat sink, that one of the main reasons for diff falure is related to a heat issue. I have had other cars with simular issues, never tried this before but I think I am going to try it this time. I think I can fab the set up for about 500.00.

Wheels
02-09-05, 05:11 PM
If I remember correctly GM has a rear diff cooler with a electric pump for use on corvettes. I think I seen it in the GM performance parts catalog for the C5R (the race version of the C5) it might be a good place to start looking for parts and info on a rear diff cooler. Good luck.

urbanski
02-09-05, 05:22 PM
sounds good! let us know the results.

6104696
02-09-05, 05:50 PM
Just got my new centersection installed and I think I am going to install a diff cooler and a pump on it. It is common knowledge that cars with low gearing , such as 3.73 tend to run a MUCH higher diff fluid temp than cars with lower gearing -3.15. I am thinking that due to the very small center section and the lack of cooling fins and the lack of large amounts of air to release the heat sink, that one of the main reasons for diff falure is related to a heat issue. I have had other cars with simular issues, never tried this before but I think I am going to try it this time. I think I can fab the set up for about 500.00.

sounds good but will it void the warranty on the rear? 4 years/50K miles of free pumpkins is not ideal but at least it's paid for.....even with the cooler a 310 ft/lb rated rear hooked up to a 395 ft/lb LS6 is bad math; it's nice to know that they are free for 4 years.

urbanski
02-09-05, 05:55 PM
you know it's funny....just today while reading something over at corvetteforum, did i realize what a "pumpkin" was
LOL

jdodman
02-09-05, 06:13 PM
Pumpkin was a term that made more sense when you look at the old posi rears from the 60's/70's muscle cars. It seems to have stuck, even though the rears today, do not resemble a pumkin quit as much as they used too.

GNSCOTT
02-09-05, 06:30 PM
I think it will be a big waste of money unless you are running your car at 100+mph for long periods of time and even then I don't know if it makes a difference. Most rears are breaking at the half shafts. There is just too much torque and weight for the rear ends to handle.

benjet
02-09-05, 06:44 PM
I think it will be a big waste of money unless you are running your car at 100+mph for long periods of time and even then I don't know if it makes a difference. Most rears are breaking at the half shafts. There is just too much torque and weight for the rear ends to handle.

I would have to agree, and I did an analysis of my 1st rear's lube, it would have shown that the lube boiled if it had overheated.

lasstss
02-09-05, 07:14 PM
I would have to agree, and I did an analysis of my 1st rear's lube, it would have shown that the lube boiled if it had overheated.

Yep, plus you have an aluminum case that sheds heat easily. My biggest gripe is that the damn thing doesent hold any oil!:hmm:

c5racr1
02-09-05, 08:13 PM
Lastss what I was thinking is that while the fluid may not be boiling, it may be too hot to relieve the stress in the gear carrier, which is very small for the application. Besides havng 3.73 gears doesn't help the issue. According to team caddy they use the stock rear? I have a younger brother, who works at a caddy dealership looking into the carrier that the STS V has, It is built on the same basic chassis that the CTS V is. The standard sts has the same rear as ours. I hope the parts will interchange if the sts v has a beefed unit.

wildwhl
02-09-05, 11:39 PM
Well, I have some input on this as just today my dealer decided that the limited slip has acutally become a bit of a "mini-spool" if you will - the diff has basically froze up. Today they have decided that a regional rep will need to look at the car to determine how to proceed. Since it was in an accident in December where most of the impact force was transmitted directly to the rear wheel, they feel it could have been caused at that time.

I argue that since they did not add the limited slip additive when the rear diff was replaced some 4,000 miles ago, that likely chewed things up.

Regardless, what is occuring now is that the fluid heats up and vents out of the top diff vent. The fluid was changed by the dealer only 800 miles ago, and today the diff was about a quart low. All of that fluid had blown through the top of the vent.

So, one way or another, diff #3 will have to be installed in this car. I have to agree that additional cooling may help the problem - but quite frankly am of the opinion that the Getrag unit spec'd is not of sufficient design to handle the specific output of the LS6 in this car. This diff was not subjected to wheel hop or ANY abuse. The failure is either by underdesign or lack of the limited slip additive, IMHO, since the current problem had started prior to the accident and the dealer elected to change the fluid when the car was in for repairs to see if that made things any better.

Makes me think I'd better called Magnuson up and drop off the pilot list for the Mag I/C :(

CTSV05
02-10-05, 10:31 AM
Well, I know this isn't a good spot for those having trouble. But at least the good side is, the more of these problems the engineers must personally deal with, it may bring a widespread solution to all of the cars that remain under warranty someday soon.

trukk
02-10-05, 02:33 PM
Just got my new centersection installed and I think I am going to install a diff cooler and a pump on it. It is common knowledge that cars with low gearing , such as 3.73 tend to run a MUCH higher diff fluid temp than cars with lower gearing -3.15. I am thinking that due to the very small center section and the lack of cooling fins and the lack of large amounts of air to release the heat sink, that one of the main reasons for diff falure is related to a heat issue. I have had other cars with simular issues, never tried this before but I think I am going to try it this time. I think I can fab the set up for about 500.00.


Just FYI. Someone over at ls1tech cts-v forums is selling a Diff cooler, $1195, amoung many other CTS-V parts.

http://www.ls1tech.com/forums/showthread.php?t=233306

-Chris

GNSCOTT
02-10-05, 02:39 PM
While I am no expert on rears, I beleive that the GM diff additive is just an anti chatter additive and that not using it causes no ill affects besides noise, but I could be wrong on that.

I also don't know how you would test to see if the cooler works anyways. There are plenty of them out there now with no rear problems at all with no cooler.

c5racr1
02-10-05, 03:15 PM
I am goning to put temp sensors on the inlet and outlet of the coolers. BTW I plan on installing the cooler at the front of the vehicle with 3/8 line with a 1-2 gph pump. I figure it should gild an extra 3/4 quart of fluid, which in itself should help.and use redline shock proof fluid. and the pump should pump slow enough to give the fluid time to cool. Might work, might not only one way to find out. BTW I can build a setup for 500-600 the 1100 price is kinda high! I planed on taking my v to a road course so it will be added insurance. worse case it goes out again and I get another one.

wildwhl
02-11-05, 12:17 AM
While I am no expert on rears, I beleive that the GM diff additive is just an anti chatter additive and that not using it causes no ill affects besides noise, but I could be wrong on that.

I also don't know how you would test to see if the cooler works anyways. There are plenty of them out there now with no rear problems at all with no cooler.

You could be right on the additive, but I know it definately chattered before the additive and now it is truly, well, terrible. When they added the LS additive about 800 miles ago everything seemed great (did a fluid change at the same time).

At any rate, the rear diff is failing again, and their current stance is due to heat. :helpless:

6104696
02-11-05, 07:23 AM
While I am no expert on rears

So....you're more of a boob man? :histeric:

dhg

(somebody had to do it...)