the other day I got on the gas on my 89 IROC and I heard a loud thump coming from under the car. It did it again consistently everytime I would floor it from a stop. Naturally I figured it was the torque arm and I would ease up and look at it later. When I finally did, it was the from of the driveshaft part. Yoke? Hitting my floor. What would cause this. Again I checked the torque arm, seems tight, the bushing at the rear of the tranny is there bud did seem squishy, but I didn't think it was all that bad. Does that have to be fairly hard, or is there something else I can check.

Thanks
Chris Diedrick

Sounds like a tranny or motor mount.

Tranny Mount. I've had 2 do this to me. Go to Autozone get the Energy suspension tranny mount for like $22, its a poly not rubber (last longer + better). Should be in stock PN-311.8 I believe but dont quote me on it lol. Also its listed under the Performance tranny mount on thier computer if you have a dummy behind the counter.

Tranny mount FTW

http://supplespub.com/cars/project-b...progress-made/

Thanks guys, I will start with the tranny mount and go from there. Easier than a motor mount ya know.

Easy way to tell if its the tranny mount is to put the car on stands, and jack up the tranny end by jacking on the torque arm bracket. Just give her a few pumps and if the tranny mount comes apart into two pieces, you have your problem.

Sounds like the tranny mount to me. I had it happen to me twice. Once on my 87 TA and the other on my 87F'bird. Its a fairly easy job from what I remember. The second time I had the problem was with the TA and I found one one (poly one mentioned bove y somebody) for 6$. I think it was suppose to be like 30, but for some reason it was marked down. The guy thought it was wrong and called some corporate manager or area manager or something to see if he could sell it to me. I made out good as the guy gave him the ok to sell it for $6.

Thanks guys I will have time towards the end of the week to check it out. i will let all of you know.
Chris

For me it was the drive shaft u joint, had a new driveshaft made with heavy duty ones, also the torq arm rubber was worn. Now it squeels the tires into 2nd and 3rd.

If its not the tranny mount then maybe a u-joint. Ive had bad u-joints make thumping noises as they rock back and forth. I had a u-joint go out on the highway going 55 mph and it was some scary crap. Driveshafts have a pretty destructive force when your moving. It bent my output shaft and snapped the the tailhousing and destroyed my exhaust.