so when i am driving when i hit a certain speed my truck starts to vibrate very bad its not my motor mounts or up front at all but it is very bad.i have a 1990 4x4. i just replaced the clutch and the transmission. is there anything that it could be im completely stumped. any help would be great.

 

Depends like freeway speeds? if so, could just be as simple as your tires need rebalancing. mise as well get a front end alignment. if you get your tires balanced..

 

Have you checked your u-joints on the rear shaft? Usually, somewhere around 40mph (give or take) is where a faulty u-joint will start to vibrate.

 

i have a 87 on 36x14.50's and around 40mph i get the death wobble,shakes my entire pickup like the tires are gonna fall off. I can't fimd ne1 to balance b/c tires r to big????

 

I would check along driveshafts, ujoints. Also tires not being balanced can cause these symptoms. Another thing that could be wrong is bad ball joints. Also check your cv axles.

 

If you pulled the drive shaft out, when you re installed it you could of put it back in 180 in the wrong way. Ive done that and it caused me a bad vibration. Hope this helps and if it dont just ignore it!