2500HD Limited Slip

GaryP · April 6, 2006

I have a 2001 2500HD, 6.0 motor, 80,000 miles and have been noticing the rear end poping when I get off the highway and make a turn and also turning in a parking lot slow the inside tire is trying to bind up. The posi unit looks ok and the ring and pinion are not pitted. It looks like a Detroit Locker which is a sealed unit but I,m not sure. I would appreciate any advice from you pros.

Thanks, Gary

mmmikkke · April 6, 2006

6.0L on 2500HD comes with an AAM1050 axle, 10.5" ring gear, good heavy duty axle. Sounds like you already changed the lube. Did you put in synthetic lube?

Haulin' 8.1 · April 6, 2006

I had a customer with the exact same truck and problem last week. I looked through my GM manual trouble shooting chart and it seemed likely to be a sticking govenor on the posi. It requires a special tool (as far as I know) to remove the govenor unit and reattach it. So since I was really to busy to experiment I sent him to the dealer.

You'll have to find a drivetrain shop or a dealer who has the proper tools to work on the Eaton G80 govenor-type posi.

Hope this helps,

Vernon

GaryP · April 7, 2006

Thanks for the quick response and advice. Is it better to use synthetic? Also I was told it did not need the limited slip additive. I guess if it gets worse I'll have to go to the shop. I was concerned because I will be towing my 5th wheel soon.

Thanks again, Gary

ChevyTech007 · April 7, 2006

Rear Axle

Axle Lubricant (GM P/N 12378261) SAE 75W-90 Synthetic or equivalent meeting GM Specification 9986115.

Butch 02 Denali · April 7, 2006

Thanks for the quick response and advice. Is it better to use synthetic? Also I was told it did not need the limited slip additive. I guess if it gets worse I'll have to go to the shop. I was concerned because I will be towing my 5th wheel soon.
Thanks again, Gary

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Synthetic lube with a GL5 rating is required for the G80 gov lock rear diff as in the GM spec lube (above) The GL5 rating has the correct friction modifiers for any posi rear diff already in it. Using non synthetic lube without adding posi additive will cause the gov loc to stick and the clutched to grab causing the exact problems you are having. I've seen this over a dozen times now. The problem really lyes with GM's statement of "no additive needed", that is misleading. The correct GM recommended lube does already have the additive in it, what they are saying is that if you use the correct lube, no MORE additive is needed!

Change the lube to a 75W-90 synthetic. make sure it says GL5 rated (Every synthetic I've seen so far is) and your sticking problem should go away if it hasn't been damaged yet.

Silver Bullet · April 7, 2006

Exactly what Butch said. I had the same problem in the same exact truck you got. It just needed the additive or the correct lube w/ additive. I have not had the problem one time since the dealer corrected the lube. It's been 12,000 miles trouble free.