my t56 in my 96 lt1 is acting funny from 75mph and faster. its done this pretty much since it was rebuilt. never did it before the rebuild. and its done it before and after a rearend rebuild. i get a bad vibration from the shifter. and when i let off of the gas it gets worse and when i get on it will smooth it out. but the vibrations are still there. any suggestions what might cause this. im going to rebuild it when i get the money cause the syncros in 3rd and 4th are grinding.

 

Get the car on jack stands while you have someone drive it to the speed that the vibration occurs. Look at the drive shaft and see if it's wobbling. That's where I would start.

 

try having the drive shaft balanced. Its cheap so even if its not your problem you shouldn't be out much cash.

 

ok i have a two post lift to put it on. i just didnt know how it would act cause sometimes only one wheel will spin. thanks guys ill let you know this week end.

 

Did you put an aftermarket clutch in? I have this same problem and it occurs when I'm maintaining 2000 RPM's. The vibration is always there but that is when its at its worst. I can feel it in my *** of the seat. I had the clutch repulled and set thinking it may be off centered (which really isnt very possible) but that wasn't the case.

Turns out that aftermarket clutches sometimes come off balanced and give you a slite vibration. After calling the company the told me that things like that are expected out of a performance clutch!!

I say F that!!

 

no my clutch is stock replacement. i beleive it did it before the replacement of the clutch. i had the tires rotated and balanced and it got better on how the car rode. but the vibrations still there. i can shift at 5 grand and no vibration. i can also down **** from 4th to 2nd and get the same vibration.

 

I would recheck the mounts. Especially the torque arm mounts.

 

i beleive that my torque arm mount looked wore out but i didnt think it was that bad.

 

i'm literally in your EXACT same situation, rear axle rebuild and all, i'm going to start with the driveshaft and go from there

 

if you get it figured out before i do please post.

 

Sounds like the Drive Shaft.. get an LS1 Aluminum one.

 

it has a spicer aluminum one on it.