Vibration

[wick]

Need some help here. I cant for the life of me figure it out. My '89 GT has the nastiest vibration you could ever imagine. What is going on is at around 45 or so it starts. It gets so bad that you cant see out of the mirrors. Now, its comming from the rear. It all started from a U-joint change. I changed driveshafts and still have the same thing. I have tried different combo's with the driveshafts. It was marked and put back on the right way. I measured the U-joints and they are withen .003 from side to side. I shut the car down while going down the highway and its still there, that eliminated the motor. I re-built the trans last weekend and put a new tailshaft bushing in. That helped a tiny bit but its still there. I pulled the wheels and drums off and started it. Still there. Its something in the rear. Any ideas? I am thinking the only thing left is the axles or something in the rear. A question I also have is can I run it with the axles out and just the carrier in? There are no noises at all. I cant for the life of me figure this out. I did put solid motor mounts in...but it was fine until the U-joint swap. Even after swapping different driveshafts in its still there. So that rules out the joints.

[Silverhatch]

Ever wheel hop it before? Although I have never heard of anyone personally bending an axle. Maybe the bearings in the back are going bad and you never realized it before because of the bad universals? I would find it hard to believe that something in the rear is bent that bad if you never severely beat on it.

[wick]

Ever wheel hop it before? Although I have never heard of anyone personally bending an axle. Maybe the bearings in the back are going bad and you never realized it before because of the bad universals? I would find it hard to believe that something in the rear is bent that bad if you never severely beat on it.

Tell you the truth Brian, I really dont beat on it. I actually baby it most of the time. I have a ton of money invested and dont want to destroy it. I have taken it to the track with the 5 lug axles. It always had a mild vibration but nothing like it is now with the new joints. I finshed my old tires off the "proper" way right before I put the universals in. Tires on Friday and uni's on Saturday. Driving home from my buddies shop after putting the tires on it was fine except for the mild vibration it always had. Change the joints and I cant even drive it now. Ed gave me another known good shaft and that did not work, Colin gave me one too and that did the same thing too. Could something bad in the rear surface and become felt with new tighter joints?

[blkp42e]

exhaust maybe rattling underneith?

[coralcoupe1993]

exhaust maybe rattling underneith?

No. It is somthing in the drive train.

[coralcoupe1993]

Tell you the truth Brian, I really dont beat on it. I actually baby it most of the time. I have a ton of money invested and dont want to destroy it. I have taken it to the track with the 5 lug axles. It always had a mild vibration but nothing like it is now with the new joints. I finshed my old tires off the "proper" way right before I put the universals in. Tires on Friday and uni's on Saturday. Driving home from my buddies shop after putting the tires on it was fine except for the mild vibration it always had. Change the joints and I cant even drive it now. Ed gave me another known good shaft and that did not work, Colin gave me one too and that did the same thing too. Could something bad in the rear surface and become felt with new tighter joints?

The old U-joint was SO BAD that it was eating up a lot of the vibration. with the new tight U joints, you feel more of the vibration.

That was the case with my GT. When I did the new control arms, my vibration got worse because less energy was being wasted with the new bushings.

[wick]

^^^^ I think I might pull the differential out tonight and run it to see what happens. That would eliminate the axles and gears.

[J-rod]

could be the gearing....somehow wear down and misaligned.... or not angled perfect...and with the new solid joints...it has less give and you feel it more.

btw rob...wtf you doing on this time of day :)