I did a search but couldn't find the exact problem I am having. I recently did an Engine/Tranny swap from a wrecked 95 GT to my 94 GT, and the tranny is a T-5 WC with the 2.95 gear and practically brand new. I was using the driveshaft that came with the car which was a stock AODE driveshaft (since that car underwent a swap) which has that stinkin' rubber balance thing on it. I noticed considerable vibration on the interstate which would fluctuate on and off at speed. I ended up breaking an axle at the track shortly after that (unrelated) and I just put new axles and a diff in there this weekend. I also put back my original 5 speed stock driveshaft with a new U-joint on the front. The vibration is not as bad now, but at above 50 or so whenever I let off the gas I feel it. As long as I keep a load on the car it doesn't vibrate. Any ideas? I think the rearend is fine as everything sounds great.