I am turning to the forum to try and help me diagnose the real source of my problems.I have a 2008 z51 corvette. I hadat a dragstrip for the first time. I am more into roadcourse racing and have never been on the 1/4 mile. I experienced alot of wheel hop which apparently broke my bell housing. We discovered 3 of the 5 bolts were missing that hold the torque tube on when I brought the car in to replace a clutch. In between the clutch replacement and the drag race event I attended Poconos raceway with no issues. I had the car running at 170+ mph without any indication of a problem. I did have clutch chatter when everything was hot in first gear putting the car on the trailer which is why I brought it in for the clutch. After the clutch install I decided to run the car before putting it back on the trailer to feel the new setup. I pulled out of the shop, shifted into second and the rear end blew up. I am assuming I damaged it at the dragstrip, and am also assuming I was very lucky it didn't give way at speed. Anyway, we push the car back into the shop and we have the rear rebuilt. I get the car back and everything appears fine until approx. 200 miles as the noise coming from the rear becomes unbearable. There was no noticiblnoise when I first drove it. So back it goes. I am told that there is no way there is a setup issue and that there has been reports of gear manufacturing that is causing a nationwide problem. This problem is coming from a hardening process. So I was told that the shop has a set of gears from last year that have nothing to do with the manufacturing process that is giving the nation problems. I get the car back and once again after 200 miles the car starts to whine. Now i'm told that there is no way it is a setup issue and there must be something else causing the gears to start making noise. Possibly a bent output shaft on the tranny. I don't know if I want to bring it to the same guy to work on or is there really a major problem that is causing this and its not his fault? If the shaft was bent,( if it could bend without breaking) wouldn't I have felt that running 170mph with no vibration? Is there a problem with gear manufaturing now across the country? Could I have the same problem on both set of gears manufactered at different times? He told me he changed the bearings and the races and all the internal parts and that it is not a setup issue. Sorry for the long post but I wanted you to have all of the information I have. Thanks for some help.

 

If you crack the case on the rear, it usually bends the transmission output shaft. The shop should check the runout of the output shaft when the rear is removed. Sounds like you have a bent output shaft.

 

Wouldn't I feel vibration when driving if the shaft was bent?

 

No. It doesn't need to be bent much to screw up a set of gears.

What broke on your rear? Breaking an output shaft doesn't usually bend a trans output shaft but cracking the case surely does. If you cracked your case and had two sets of gears go bad...I bet the trans output shaft is your problem.

Sorry to bring bad news but if that's it, you'll need a trans rebuild and they aren't cheap.

I know all this stuff because I've been there. My output shaft was just a little bent but my shop told me if I'd left it my gears wouldn't last.

 

I didn't break the case but I did break the ring and pinion. Both were missing teeth. The break happened at slow speed at 20-30 mph.

 

You'll need to check the runout.

I did get a bad set of 3.90 gears a few years ago, similar situation as yours, they went bad after couple hundred miles, they whined like nobody's business on decel. There were none to be found when I needed them so I went with 4:10's and I'm very happy I did. They are still quiet to this day.

 

I'd find a new shop. It sounds like your guy doesn't know what he's doing.

 

BLACKJACK08,
I would recommend taking it in for a second opinion. If you send me your zip code I should be able to provide you with the information of some good dealerships within 100 miles of where you live.

Chevrolet Customer Service,
Justin

 

pm sent

 

Another output shaft vote in agreement with Joe_G.

As he knows, I've been through four transmissions and differentials now, and a bent output shaft, even only a couple thousandths out of spec, can destroy the ring and pinion by way of deflection caused by premature bearing wear. Not saying it's a guarantee, but some of us have been there and experienced this.

If the pinion bearing is being beat by a wobbling output, it will allow the actual pinion to back out of the case, increasing the amount of lash between it and the ring, and minimizing contact patch. This poor mesh will create a ton of noise, exacerbate the problem, and eventually the pinion and/or ring will shear teeth off one another- either by the pinion finally backing into the inspection cover on the diff, or just good old fashion wear.

Either way, with this many differential failures, I'd say it'd be almost a miracle if your output shaft was still running true. Sorry man.

 

im going to have the tranny pulled and check the run out. I will keep you posted.

 

If you're feeling up to it, you can save a hell of a lot of money by pulling the transmission yourself. I've got a good write-up on the process with plenty of pics to help you along. It's actually quite simple, and just takes a little time and elbow grease.