[Jason18ZL1LE]

Anyone here have their rear differential replaced for whirring on deceleration? This is usually indicative of a bad ring/pinion lash or bad bearing. Im curious as to how GM handled it. Did they replace the diff entirely or did they replace the bearing?

My 2018 ZL1 1LE has 11,300 but I do have mods like CAM, headers etc so I fully expect them to try and not cover the rear end, even though the car has only been tracked twice and never even attempted a launch since we all know the M6 cant launch anyway.

Thoughts?

Here is a link to the sound.

[BMWM.D.]

Damn, that sounds pretty annoying. Not that it really matters now, but have you changed the diff fluid at all?

[Jason18ZL1LE]

It was serviced at 1500 miles per the recommendation. Past that it hadn’t been changed. The diff actually doesn’t make any noise at all until the fluid warms up so I’m going to drain and fill the diff in the next day or so and see what happens.

I don’t launch the car at all and rarely do any straight lines pulls of any significance so I don’t know how the pinion preload could have loosened, which is usually what this noise is

[Michael2000]

That's pretty loud. I would get it looked at. I don't think new fluid will do much for that.

[BMWM.D.]

Originally Posted by Jason18ZL1LE

It was serviced at 1500 miles per the recommendation. Past that it hadn’t been changed. The diff actually doesn’t make any noise at all until the fluid warms up so I’m going to drain and fill the diff in the next day or so and see what happens.

I don’t launch the car at all and rarely do any straight lines pulls of any significance so I don’t know how the pinion preload could have loosened, which is usually what this noise is

I was just curious, as my fluid looked like crap when I drained it at 500 miles. I’m glad I got the break in lube out of there when I did. Then I did another at 1500. Looked much better that time. All my years of doing run-in services on M3s, M5s, etc. is what prompted me to do that. The diff fluid on those always looks horrible at 1000-1200 miles.

That reminds me that I should probably do mine again soon. Like you, I’m modified and likely on my own for many warranty issues. I’ve always seen fluid changes as cheap insurance. Not saying that would have prevented this. Could just be a fluke failure.

[SJFGTO]

Once the whine gets to that point for any length of time, fluid change will not fix anything. Need to see the dealer.

[BMWM.D.]

Originally Posted by SJFGTO

Once the whine gets to that point for any length of time, fluid change will not fix anything. Need to see the dealer.

If that was directed at me, that wasn’t at all what I was implying. Just wonder if preventative maintenance might have stopped this from happening.

[Jason18ZL1LE]

Originally Posted by SJFGTO

Once the whine gets to that point for any length of time, fluid change will not fix anything. Need to see the dealer.

I’m planning to see the dealer. My post wasn’t about whether or not it could be saved. I was asking what people’s experience with drivetrain warranty with modified engines. I’m sure they will fight me but just wanted to see what others had experienced.

[SJFGTO]

Hard to say, very dealer specific. I come from a long line of Chevy dealers in my family. Warranty work can be a money loser for dealers as GM will not always fully reimburse the dealer for his cost of warranty service. I could easily see and in fact have personal knowledge of one dealer denying warranty work on a noisy rear end on a Corvette with a mildly modified engine. Then it can become an expensive pissing contest with dealer about proof that the modifications caused the failure. So, although I know of only one example, it is a realistic possibility they may fight you. Insist on specific proof that the mods caused the rearend failure. You might want to ask around about which dealers in your area are more mod friendly, if any.

[Jason18ZL1LE]

I’ve got some feelers out from my builder to try and get this handled. If I’m out of pocket it will be about $3k, at which time we will probably do a 9” or something better

[BMWM.D.]

Originally Posted by Jason18ZL1LE

I’ve got some feelers out from my builder to try and get this handled. If I’m out of pocket it will be about $3k, at which time we will probably do a 9” or something better

If you can get in touch with a good dealer, they might help you out. I feel like if it’s a known issue or something they’ve seen before, you’ll be in the clear. I have a great mom & pop type of dealer near me, but that would probably be a few hour drive for you.

By the way, do you happen to know a Porsche/McLaren tech named Dave?

[Michael2000]

Problem is you are putting more power to the rear end than what it was designed and tested for. That certainly would be grounds for warranty denial.

[Jason18ZL1LE]

The rear end is built for way more power and yes, I’m aware of what their position will be.

[tomster]

What was the fix? I have the exact same noise coming from my 2022