here at the shop we have done 3 11.5 rears this week. one was for total destruction, abuse problem. the other 2 were new low mile 07 classics. came in for chatter problems. replaced the clutch packs. any other techs seeing this trend at there shops?

here at the shop we have done 3 11.5 rears this week. one was for total destruction, abuse problem. the other 2 were new low mile 07 classics. came in for chatter problems. replaced the clutch packs. any other techs seeing this trend at there shops?

Rear diff chatter in the 11.5 is almost always from wrong fluid, or wrong fluid and limited slip additive.

As far as other failures, i've seen a few in the last few years. "johnny" driving dads truck doing donuts, ("my son would never do that!":mad: - "I don't know what all that black stuff is in the wheel wells"):) , Plow/sander trucks abused by employees, WATCH out for GL-4 induced chatter/failure! I've seen a tech drain and fill rear diff at 3k service with gl-4 instead, (moron didn't know) , and well, they came back howling, less than 1000 miles later. I inspected the gear faces, and you wouldn't believe the wear pattern with 3-5 for backlash, looked like 300k miles. Needless to say GM bought ring and pinion for those two trucks. I've seen a few others that were noisy that the owner had recently changed the gear lube, with non-synthetic gl-4 with and without additive. Lube does make a difference<rant to follow> I know many people reading this might think I'm a jerk for saying this , but GM adds the "grape" flavoring to track warranty failures, and I know nobody likes to waste money , but I've seen alot of people ask "what's the cheapest lube for my truck, I'm not paying $29 for GM grape (rape-me ) fluid?" Hmmm, ... I just paid 50k for a truck, but now $120 for fluid is going to break me, I'll put in brand x-junk, it's all the same. Heck , i'm changing my engine oil anyway, I'll just use that oil too. I know Mobil 1(I love Amsoil btw) and others make excellent fluid for this application, but why not use the fluid GM specs for it? The difference might equal the price of one tank of fuel. Back to reality , Without oil analysis you can't tell what oil is in there (gl-4 or 5), but I'm happier when I smell grape.

yeah your right about the fluid. even here at the dealership they do it. we run out so we just order some syn from napa. imo it is not the same. but any way. yeah both trucks were still on the factory fluid, less than 3000 miles. both 07's. kinda odd.

yeah your right about the fluid. even here at the dealership they do it. we run out so we just order some syn from napa. imo it is not the same. but any way. yeah both trucks were still on the factory fluid, less than 3000 miles. both 07's. kinda odd.

I just remembered a while back there was a run of bad rear ends in cts's, and aftertalking to techline , they hinted about contaminated lube at factory, something about salt water leaching into shipping drums of lube... maybe something similar here?