Rear Diff Cover for Cooling..

[Wheeler]

Wow lots of advice/opinions on this one. I did read elsewhere like was mentioned about the 75-140 being the better option.. I do run between 3k to 3500rpm towing heavy for hours at a time. I’ll have to do a bit more homework before I make a choice.. I do like the idea that some aftermarket covers allow u to have more fluid…

 

[DerekTheGreat]

You don't need more fluid. And those aftermarket covers which increase capacity, are they flat back style? If so, waste of money and would cause the oil to be overworked as the ring gear is going to throw oil right at the cover & it'll shear, increasing heat generation. Not to mention that radius that the stock covers have helps oil get carried over to the pinion slinger.

 

[Wheeler]

I agree about the flat back.. after watching the video posted here makes perfect sense.. I’m starting to think just more fluid changes the way to go…

 

[stutaeng]

Yes, I think that's a better proposition. Engine oil brand, type and change interval get people excited really fast. Everyone has an opinion and some think only they are correct, LOL.

Air filters, on the other hand, must never (or hardly) ever get replaced. I never seen a thread on air filters. Ditto for differential fluid changes...

 

[red98]

I agree about the flat back.. after watching the video posted here makes perfect sense.. I’m starting to think just more fluid changes the way to go…

Considering 90% of these gmt400s on the road have probably been running the same rear end fluid for 10+ years this sounds like a plan LOL.

 

[454cid]

I broke the spider gears in the 8.5 that came stock in my Express van shortly after swapping to the 4L85E and starting to tow with it regularly. When I tore into it the spider gears were the least of my worries. The axles, axle bearings, pinon bearings and ring and pinon were all blue from overheating (fluid level was not low and I had less than 90K on it) and the whole rear end was trashed. Swapped it for an 9.5 that I had redrilled 5 on 5 and ran with it. I have since swapped the 9.5 for a 10.5 with added fluid and a finned cover for better cooling.

You were either over working it, or it was defective to begin with.

 

[df2x4]

I did read elsewhere like was mentioned about the 75-140 being the better option..

Be aware that if you have the factory G80 locker you should run GL5 80W-90 with no friction modifiers or additives according to GM. There's a TSB on it.

 

[Wheeler]

Yes I read up on that. I do have a posi rear end.

 

[Frank Enstein]

I use Redline Heavy Weight Shockproof gear lube. It is a 75w90 gear lube with a film strength higher than a 250 weight gear lube. Redline says it has micro size ball bearings that prevent metal to metal contact.

Red Line Synthetic Oil 58204 Red Line Heavy ShockProof Gear Oil | Summit Racing

Free Shipping - Red Line Heavy ShockProof Gear Oil with qualifying orders of $109. Shop Gear Oil at Summit Racing.

www.summitracing.com

Banks's website is down currently but I didn't see a cover from them for the 9.5 sf axle. Fins on the cover do very little unless you have directed air flow like the videos show. They might make it cool off a little better when parked.

You could run an electric pump and a fluid cooler but it is overkill. It's better to just use good fluid and change it as needed.

 

[L31MaxExpress]

You were either over working it, or it was defective to begin with.

Well if it was overworked it was a GM fault as it was a stock setup at the time that did not have a hitch. It was turning the fluid black even at low mileage when it still had a stock engine and 4L60E. Never made any noise until the spider gears grenaded.