ZL1 Rear Differential Failure!

[ZO6 Bryan]

Brand new rear end gears need break-in before putting a full load on them. Sure someone didn't romp on it to hard before the ring and pinion were worn in?

[xx_ED_xx]

Probably forgot to put oil in it....

[2010 SS RS]

yeah LPE has been selling those very same American Gears 373's for some time now until GM grabbed all the stock up to build these rear ends.

I know two guys with them and they both had a specific break in schedule for them. And yeah you can sure hear them... but its a good thing not a bad thing. Also god only knows but he could be hearing some of the whine from the SC as well. All of these little issues can be attributed to the unknown sounds that no-one has ever heard before. But in reality it is the sounds that only will be emitted by a ZL1.

This is not an SS set up and in no way should be compared to it.

The set up on the AG 373 is so much nicer than the set up and spacers required on the 391's and 410's from the un named aftermarket competition...lol

Hopefully someone like Scott that has been in a test vehicle will chime in and confirm the gear sounds and break in requirements which will set folks at ease a bit. Or most of the guys that have done gear mods can confirm this difference as well. I really dont think there is an issue and would hate to see this get blown out of proportion and turn into something that everyone thinks they are having a problem. This is more than likely exactly what a brand new AG 373 is supposed to sound like.

Just sayin!

[2010 SS RS]

Originally Posted by mlee

Excellent point... that rear end isn't even broken in yet. They can always swap it later if it's really a problem...

Yeah you for one should know about these gears and for that matter any gears like this set up. I am just amazed the dealer is finding it odd. Of course like I said if they are comparing to SS they are in for a surprise when they put the new ones in and find it is the same...

And they may just find out that GM will want it to go thru the break in period before the swap anyway. Geez.. If they replaced exhaust systems because they smelled when new GM would go broke.

[Mr. Wyndham]

Originally Posted by PYROLYSIS

I was thinking the same thing, but these rearends are supposed to be indestructable. Probably just a rare bad part.

That's what I'm thinking...

Sorry for your luck, mcamisgroup! Hope everything moves along quickly!

[Faulkner]

Wow I didn't know a test drive was part of a PDI. I think someone went out and beat your car and now are making excuses.

[NASCR3]

Originally Posted by PYROLYSIS

I was thinking the same thing, but these rearends are supposed to be indestructable. Probably just a rare bad part.

The Titanic was "indestructable" too.

[2012ZL1]

Originally Posted by Faulkner

Wow I didn't know a test drive was part of a PDI. I think someone went out and beat your car and now are making excuses.

[GearheadSS]

Originally Posted by Faulkner

Wow I didn't know a test drive was part of a PDI. I think someone went out and beat your car and now are making excuses.

It is if the tech does his job correctly. Every car should be test driven to make sure that the customer doesn't find something when they drive it.

I saw a new 2500HD with an oil line let loose on a PDI test drive before. Technician was watching his gauges like he was supposed to and saw the sudden drop in oil pressure and shut the thing down on the street. Another tech brought some tools and oil and they fixed it on the side of the road.

[hairtrigger]

Originally Posted by mcamisgroup

I was supposed to pick up my 2012 Ashen Gray ZL1 at my dealership today at 5pm after PDI. As part of the PDI, a technician who I respect, took the car for a short test drive to make sure everything was perfect. I got a call from my service manager saying that the rear end is bad and whining distinctively at low speeds. They have ordered a whole new rear end to be Fed-exed tomorrow and hopefully installed by tomorrow night.

Of course I am really upset and want to get your opinions on what this really means since I am not a technician. Will the car be the same after a complete rear end replacement? Does this mean I have received a lemon? Was this an assembly line error or was it just a defective major part? By the way, it sat in QC for 4 weeks with the others.

Let them install the new rear. Be sure to take a test drive with a tech after it is done. Ask them what it sounded like before and after the replacement. It's your expensive car and you need to know that that was what they were hearing in the first place. I personally would have gone for a drive myself to hear the noise before they pulled out the wrenches.

[Unobtainium]

Brutal. Seems odd. Another delay. Feel sorry for your nerves. Hopefully the new set-up is bullet proof for you.

[SixGracing]

I've never heard of a technician driving a car to make sure it's ok. Isn't that what quality does at the GM plant? Not to mention, if I'm spending upwards of $60K for a car I don't want ANYONE driving my car other than taking it off the truck. I would be pissed and I would be asking a lot of questions. I think your tech friend did you a bad favor. Just my opinion of course. But I would have left instructions with the dealer that NO ONE drives the car. Period!

[VA SSHEVY]

Originally Posted by SixGracing

I've never heard of a technician driving a car to make sure it's ok. ...

I took my Z06 in for a recall on a gas cap or some such nonsense. Set my Window Valet to reflect high speed driven. Clocked the tech doing 52 mph in "the parking lot". Why would think that I was asked. Showed them. Busted!

[AMCBimmer]

For other manufactures a PDI does require you to drive the vehicle. This is completely normal. Audi for examply drives their R8's for 30-50 miles before the car is even delivered to the dealership.