Extreme engine vibration (especially while in reverse)

[22catch22]

Just finished putting a remanufactured engine in my stang. Everything runs great except this vibration. The vibration isn't too bad until the car is put into reverse. The minute I shift into drive or neutral, the vibration minimizes. I have no idea what it could be. The engine mounts
and the transmission mounts were replaced during the motor swap. I also put in a new vibration damper. I've rechecked all of the bolts numerous times. I took it to a transmission specialist to ensure that the torque converter wasn't loose. Any ideas??

 

[Chythar]

Sounds like the engine isn't balance right to me. the 94-95 5.0's use a 50oz vibration dampener and a 50oz flywheel/flexplate. The old weight was 28oz. To mix those parts is a very bad thing.

 

[22catch22]

I was informed of this weight difference while doing the swap, so I made sure that the new engine was balanced at the same weight as the old engine. Thanks for the reply.

 

[94 Black GT]

could it be a driveshaft problem? i had a strange vibration and come to find out the rear d/s bolts were loose..thank god i didnt catapult myself..just a thought

 

[302GTS]

could it be a driveshaft problem? i had a strange vibration and come to find out the rear d/s bolts were loose..thank god i didnt catapult myself..just a thought

Had the same problem with my 95 - I didn't tighten the d/s bolts enough last time I had it out. Luckily I fixed the problem right after noticing the vibration.