2000 Z28 w/ 3.73 gears Nasty Vibration at 78-88 mph

[gokussx4]

I bought the car with 3.73 gears in it. Had the ring and pinion replaced with a new installation kit (replaced by performance shop). Still no change. Had new tires put on (Bridgestone potenza). Performance shop says the stock rear end in a camaro cannot handle the 3.73 gear, says i need to get a mosher rear end to solve the issue. The car vibrates less over 90 mph.
I am tempted now to switch back to the 2.72 original gear to see if it is the issue but I don't want to pay 600 bucks as a test.

Anyone have any ideas on what I could get done to get rid of the vibration?

[~Firehawk~]

does the car have an aftermarket exhaust on it?

I changed my flywheel, gears and did a full exhaust at the same time. I got a nasty vibraion like you discribed and it was a solid vibration through the car. I thought it was the flywheel so I changed it again, then i changed the gears again...never did I think it would be the exhaust making the vibration. Once I changed the exhaust the vibration went away. So are you 100% sure its the gears? I have 3.73's in my 02 hawk and I dont get vibration from it at all. IF its not the exhaust then I would try balancing all 4 tires.

[gokussx4]

To be honest I had this problem with the original exhaust but I do have a flowmaster cat back 80 series on it now. I did have a rubber mount put in by my local performance shop but that didn't help either. I had all 4 tires balanced as well by firestone. What exhaust do you have on yours now?

[~Firehawk~]

when I had the vibrationI had kooks LT's no cats and a true dual with x pipe using (2) sweet thunder mufflers

Now I have kooks LT's kooks ORY and gmmg catback

If you have the capability try to take off your muffler and drive down the block to see if the vibration is still there. If its gone you know its your exhaust. But be careful, when I drive with open headers and just the ORY I get more vibration. Try to leave on your cats (if youhave them) and as much of the pipes as you can that goes on before the muffler.

[Hawk241]

I would carfax the car, or did you. Maybe it was in a collision, not enough to salvage just enough to throw its balance off.

[gokussx4]

I just had the cats gutted and found misfires :( another subject

The guy who had the car before me raced it and nothing was put through insurance so its very possible something happened that I don't know about.

Any recommendations with the cats being gutted?? Should i look to replace the exhaust system from the block down?

[maroonZ]

get your pinion angle checked.

If it is out of the factory tolerance it could cause a bad vibration

[BlwnCamaro]

also very likely it could have a bent or out of balance driveshaft. Had similar experience before and it was the driveshaft.

[turbotko]

I also have a very strong vibration felt throughout the car although it is at a different speed than yours (45-60mph). I also have a flowmaster 80 series exhaust and I've noticed that it only vibrates in 3rd gear (A4 tranny). When It vibrates if I shift to overdrive the vibration immediately goes away. Downshifting back to 3rd brings it right back.

I haven't been worried about it because the fact that shifting gears changes it indicates it's not a driveshaft/rear-end problem. It's more rpm related than speed related. Interesting bit about the flowmasters though........you guys may be on to something here.

[lvlcapblue]

About the before mentioned drive shaft...
Had a friend with a 60's Charger, forget what year, but when he had the entire tranny rebuilt he had some nasty vibrations that actually threw the car out of gear. Gutted the tranny and tried again only to find the vibration was a sticky "U-joint." Maybe you should check for that.