Hey guys,

Recently finished a 700r4 to T5 swap in my 91 Trans Am. Engine is the stock 305 TPI and the rear end is a 3.45 9-bolt. Prior to the swap, the car (while not perfect) was considerably smoother with the automatic. Now it vibrates a considerable amount at 55+ mph. The vibrations are tolerable while cruising in 5th but if I downshift into 4th or even 3rd to pass someone, it becomes really bad. There's also a random rattling coming from under the car somewhere, and I've noticed it gets worse with a passenger in the car.

I will be going under the car this weekend to take a look however so far people have suggested that I flip the driveshaft 180 degrees (stock aluminum unit by the way). I also have a polyurethane transmission mount; had a stock rubber one with the automatic. I hear that they'll worsen vibrations but can they really increase them that significantly? Any other suggestions would be great, thanks!

 

Yes.

 

Extension housing bushing

 

Mind elaborating?

 

My mind is not very elaborate.



Seriously:

The drive shaft yoke slides into a bushing in the extension housing, the rearmost piece of the transmission. The bushing supports the front end of the shaft. If it's loose, the shaft wallows all around up in there. It frequently wears out, esp when the trans is allowed to run low or dry, as T-5s, esp 1st design, often do.