VIBRATIONS AT 65 MPH

my truck has been bagged for about a year and a half. and it is just now starting to vibrate really bad whenever i hit 65 mph or more. however, it only lasts like 20 or 30 minutes and then it gets better. it does it at any ride height. it is a one piece drive shaft and my truck is a 92 toyota. i have a forward triangulated four link. after i had it bagged, the driveshaft would push in to the transmission with the back down real low, and my four link is adjustable so i moved the axle back like 1/2" and that solved the problem. but im not sure if that is contributing to my problem now. Is there a way to find out the correct distance from my axle to the transmission so that the driveshaft won't push in or pull out of the transmission too much? or could something else by causing this problem?

SOUNDS TO ME LIKE THE PINION ANGLE IS OFF A BIT !!!!

you might missing some weights off a wheel also.

ive been having a similar problem in my 88. since the truck has been bagged (2+ years ago) i havent once messed with the link bars. at first i thought it was a balance issue with my tires so i put the truck in the shop had all tires rotated from left to right balanced and the front end alligned...its still doing it. i did replace my 4 speed tranny with a 5 speed tranny a few weeks ago and it seems as thought he problem started about a week after that. both trannys dimensions are identical to one another as far as length goes. i only have a mono shock in the rear, if the shock were bad could it cause minor wheel hop at those speeds? sorry i dont mean to jack your thread by no means but i feel your pain with the vibration issue!

ill make sure that the wheels and tires are balanced. and if the pinion angle is off, wouldn't this have happened from the beginning? i'll check it anyway. can i do any further damage by driving it like this? and how can i find out if my axle is too far forward or backward, is there a set distance for this type of truck?

well your supposted to set the pinion angle for ride heigth that you would usually ride at. and your axle should be the same as wheel distance from a stock heigth truck also. thats how you should know

well i found the problem. about a month ago, i had to replace an axle seal. and the grease had leaked out a lot and slung up inside my wheel. there was so much caked up that it through the balance off of the wheel. so i cleaned it off and got everything balanced and now i have no problems. that was the last thing i expected to find.