My cherokee took a pretty heavy hit to the chassis today. It dropped onto a rock, which smushed the transmission crossmember. It still works and other than the crossmember I can't seem to see any other obvious damage, but the truck vibrates quite a bit now when approaching highway speed. What could be a likely culprit? I was thinking a tweaked driveshaft, but how would I test this? Also there are no signs of impact to the shafts themselves..

 

It's also possible you knocked the tranny out of position.
Try removing the tranny cross member and BFH'ing it back into position.

 

You also may want to check the tranny mount. Had the same issue a while back. Went to replace the crossmember with a new one and the mount fell apart. Funny, it still looked solid from the outside, but broken free inside. Anyway, the crossmember was fixed with the 16# BFH and a $11 mount.

 

Thanks guys, I have the same weird vibration and my first thought was the transmission but it vibrated in every gear.

 

Alright I'm gonna take off the crossmember to check out the tranny mount. Only thing I don't understand is that isn't the whole point of a universal joint to allow the shaft to work at different angles? If the transfer case is misaligned, it isn't by a big amount. The shafts are still at a very mellow angle, so how could that be enough to cause problems?

 

U-joints are designed to operate at an angle, however, they are only designed to operate at a narrow angle range when at speed. They also need to be at the same angle or it could create an odd harmonic. The tweaked crossmember could be causing this and/or a damaged mount amplifying the effect.