Slick 60's

The PO of my truck cut the front coils a little, and removed a few leafs in the back to give is a cheap stance. Would these two changes, change the angle of my driveshaft? I have wicked patterned vibration vrmm...vrmm...vrmm, at about 40mph. Once mechanic said the drive shaft was probably out of balance, another told me it looked like my truck went down the road with the ass sideways a bit.

I'm starting to looking to all solutions. I have someone to check the balance of the drive shaft (haven't done it yet though). But didn't know about the cutting of coils and removing leafs. To me all that happens above the drive line but i'm no mechanic.

wheel bearings?
Rear end reassembled out of line after taking out a leaf?
bad bushings?

much thanks
Gregg

lowering the truck will change the u joint angles and you will end up with the driveshaft being more in line with the diff. You do not want the driveshaft and diff to be in a straight line. The yolk into the transmission may also ne worn and the bushing in the transmission output housing may be worn which will also cause vibration.

Your driveshaft should be about 3/4" from making contact with the diff if it is bottomed out in the transmission to allow for rear spring compression. If the bump stops are still in place, it might be OK as it should have been sized to account for hitting the bump stops. A bad u-joint on either end could cause this as could many other things. Something is out of balance, engine trans, drive shaft or rear end. Drive it through wet spot on pavement or dirt/mud to check the tracking. The rear end is not as wide as the front, so it can look like you are dog running (out of track from to rear) a little even if you are dead straight. Like most mechanical things its more often an exercise in elimination to track a problem down.

if you have a slip yoke like this at the trans end the splines could be sloppy and allow vibration.
if you can wiggle it a little fill it up with grease , if you can wiggle it a lot its probably worn out and needs replacing.
since your truck had springs removed and its not as stiff the more it moves up and down the more wear on the splines.

Flywheel/flex plate possibility as well. Seen a few of those cheap after market ones cause all sorts of vibration problems.