Rear end making a winding noise and GM bulletin regarding it.

[djnice]

What do you mean flush? Did you just drain it completely and put in new fluid, or did you flush it out with something?

[joes407]

my dealer refused this repair for me because firstly by the time i get to dealer the rear is warmed up and doesnt make the noise for them and secondly because the damn service bulletin says not to do this fix on ZL-1. mine has been making this noise for 20k miles now and its worse on colder mornings

[Modern07]

Originally Posted by joes407

my dealer refused this repair for me because firstly by the time i get to dealer the rear is warmed up and doesnt make the noise for them and secondly because the damn service bulletin says not to do this fix on ZL-1. mine has been making this noise for 20k miles now and its worse on colder mornings

You need to go to a different dealer then!

Starling fixed mine without even a question - been fine ever since

[OldScoolCamaro]

Originally Posted by Al C.

Not true.. If you use the recommended rear diff fluid for the ZL1, it already has the lim slip in it.. I had the same issue.. I bought 3Qt and did the flush in my garage, problem fixed..

Sold over the counter at Chevy parts, the 1 qt. bottle of synthetic gear lube with friction inhibitor is the factory replacement lube. I changed my rear axle fluid last week. 1,600 miles. I had many of the same, normal noise issues as most others associated with the ZL1. I diagnosed mine as normal break in with a HD posi rear. Both magnetic plugs had a yellow base accumulation on them, then layered with the dark grey build up of contamination totalling approx. 1/2" thick. Also there were several small slivers of metal. I highly recommend everyone change the rear axle fluid. I will post the GM P/N later.

[The Stig]

Originally Posted by OldScoolCamaro

True. Sold over the counter at Chevy parts, the 1 qt. bottle of synthetic gear lube with friction inhibitor is the factory replacement lube. I changed my rear axle fluid last week. 1,600 miles. I had many of the same, normal noise issues as most others associated with the ZL1. I diagnosed mine as normal break in with a HD posi rear. Both magnetic plugs had a yellow base accumulation on them, then layered with the dark grey build up of contamination totqlling approx. 1/2" thick. Also there were several small slivers of metal. I highly recommend everyone change the rear axle fluid. I will post the GM P/N later.

I know I have an SS, but I saw pretty much the same gunk, crap, etc. in my fluid when I changed it at 1,500.

[Rizzo]

Originally Posted by Sven59

That bulletin is not for the ZL1, they are different, it has been confirmed here on other threads.

I had the same issue on my ZL1. The dealership still honored the TSB and changed the fluid and seals. The noise has gone away.

I have a feeling that the TSB will need to be expanded to include the ZL1

[PNYSLAR]

Originally Posted by Bowtie724

I dont drive my car as often as I want to and after 7 months I have about 4300 miles. I took it in to the dealer to have the oil changed and I mentioned the winding noise in the rear end when I am backing up out of my driveway and turning at the same time. I can hear it going forward and turning as well. I know for sure the tires are not rubbing. The dealer told me he had to order parts that there was a bulletin. Anyone heard of this? I asked him to see the copy of the bulletin, so I can look for myself.

Yes I had the same thing happen to me @5k on my 2012 ZL1. The parts they had to order for mine were seals. They had none anywhere close to the dealership and took over a week for them to arrive. Seems the 2012's have the same issue when they reach the magical reading of @5k on the odometer.

[ZO6 Bryan]

Originally Posted by Al C.

Not true.. If you use the recommended rear diff fluid for the ZL1, it already has the lim slip in it.. I had the same issue.. I bought 3Qt and did the flush in my garage, problem fixed..

I changed mine too. It comes back. Put some additive in and it will be silent.

[Al C.]

Originally Posted by djnice

What do you mean flush? Did you just drain it completely and put in new fluid, or did you flush it out with something?

Sorry bad choice of vocabulary... Drain and refill with new fluid.

Originally Posted by OldScoolCamaro

Sold over the counter at Chevy parts, the 1 qt. bottle of synthetic gear lube with friction inhibitor is the factory replacement lube. I changed my rear axle fluid last week. 1,600 miles. I had many of the same, normal noise issues as most others associated with the ZL1. I diagnosed mine as normal break in with a HD posi rear. Both magnetic plugs had a yellow base accumulation on them, then layered with the dark grey build up of contamination totalling approx. 1/2" thick. Also there were several small slivers of metal. I highly recommend everyone change the rear axle fluid. I will post the GM P/N later.

If you have to add the limited slip inhibitor, you are not using the correct fluid..
The ZL1 has a specific fluid, not like the SS, that has the inhibitor already in it and it is advised NOT to add any additional lim slip.
GM PART NUMBER: 88862624. My plugs looked like what u described when I drained the rear end and I agree fork out the $70-80 to change ur diff fluid.. If that doesn't work, which it will, take to the dealer..

Originally Posted by ZO6 Bryan

I changed mine too. It comes back. Put some additive in and it will be silent.

.. If you filled with the fluid that has the inhibitor and added additional lim slip to it, not good. I'm sure it will have some "results" but definitely not advised.

[Sven59]

Originally Posted by djnice

Did this also fix the slight whinning noise that we get when lightly on the throttle at highway speed?

Yes!

[ZO6 Bryan]

Originally Posted by Al C.

Sorry bad choice of vocabulary... Drain and refill with new fluid.




If you have to add the limited slip inhibitor, you are not using the correct fluid..
The ZL1 has a specific fluid, not like the SS, that has the inhibitor already in it and it is advised NOT to add any additional lim slip.
GM PART NUMBER: 88862624. My plugs looked like what u described when I drained the rear end and I agree fork out the $70-80 to change ur diff fluid.. If that doesn't work, which it will, take to the dealer..



.. If you filled with the fluid that has the inhibitor and added additional lim slip to it, not good. I'm sure it will have some "results" but definitely not advised.

Who says that they aren't compatable? The ZL1 comes with SYTHETIC Limited Slip fluid. The SS comes with convetional limited slip fluid. There is nothing magic about the GM recommended fluid. Just stick to the synthetic fluid. The TSB for the SS has them replace the convetional LS fluid with the synthetic fluid. So there is no need to tear down the rear end to replace seals in the ZL1. This is not a new problem. Noise from clutchs in limited slip rear ends has been around since they were invented decades ago. If you had a 20 yr old car with limited slip then put the additive if its noisy. If your ZL1 is noisy do the same thing.

[Al C.]

This sums it up..


There is a downside to adding too much friction modifier. The diff clutch plates are what give the diff its limited slip ability. They are designed to grip to each other and pass torque to the tire with grip when one tire looses grip. When your fluid properties are not correct (too slippery), these clutch plates lose their friction with each other, thus the diff becomes more like an open diff.

While that might not be as much as factor on the street, you should at least recognize that adding too much modifier, while it won't hurt the diff, does cost you performance. The goal is to just have enough additive to prevent chatter and no more.

[HDRDTD]

Originally Posted by Al C.

This sums it up..


There is a downside to adding too much friction modifier. The diff clutch plates are what give the diff its limited slip ability. They are designed to grip to each other and pass torque to the tire with grip when one tire looses grip. When your fluid properties are not correct (too slippery), these clutch plates lose their friction with each other, thus the diff becomes more like an open diff.

While that might not be as much as factor on the street, you should at least recognize that adding too much modifier, while it won't hurt the diff, does cost you performance. The goal is to just have enough additive to prevent chatter and no more.

OK, stupid question....

Does the friction modifier increase or reduce the friction of the clutch plates?

[Al C.]

Adding the modifier reduces friction, less friction to the plates reduces torque to the wheels there for "less" power. if you want to increase friction you add less modifier but then you get "stick slip" or chatter. So the modifier is just that, it's used to modify the coefficiency of the diff fluid to suite you application.