When I go over large bumps at highway speeds the ujoint on my front driveshaft shaft strikes the motor near the bellhousing/ oilpan connection! This never happened before I replaced my motor. It was really bad at first so I replaced the motor mounts with the jags that run mounts. This has helped. But there is still only about 1/4" in between the driveshaft and the motor. Could it be a transmission mount? 1996 gmc jimmy 4dr 4x4

 

If you have already replaced the motor mounts, that's about the only other thing that could allow the drive shaft to hit the engine/trans besides bad u-joints which would be VERY obvious once you engaged 4wd.

 

Thanks for the insight- hopefully autozone carries the transmission mount. I replaced the front U-joint when I took the motor out so it is new.

 

they do. its like 19.99.

 

Well, I got the new mount and it fits even worse. I compared it with the old mount and it places the driveshaft even closer to the motor. It is basically almost touching the motor. The new mount is 1/4" shorter and it puts the driveshaft that much closer to the motor. I guess I'm just going to shim the trans mount up with some washers... I'm not sure what went wrong here.

New mount on left, old mount on right. My original mount looks perfectly fine by the way.

 

Have you checked front chassis ride height? It affects drive shaft angle. Just a thought.

 

How much clearance should there be between the shaft and the bellhousing?

I put the original mount back in and added a 1/4" spacer that I made out of aluminum... I'll check and see if it makes a difference tomorrow.

 

Gonna have to disagree with you there CH. IFS == front diff doesn't move.

Were the motor mounts different up front by any chance? There should be more than enough clearance and I believe that the motor mounts are different side to side which can push the motor around. How does the fan look in the fan shroud?

And that mount doesn't look right for your truck. A replacement shouldn't be shorter...

 

IIRC the crossmember that the mount bolts to can be installed either way, but there's an arrow pointing to "FRONT" stamped in the crossmember.

 

Correct, front differential doesn't move, but the frame does, and the trans is bolted to the frame.