Bad vibes...

[Subliminal]

So, I've had this problem (in various forms) for as long as I've had the truck. The current issue:

When I get up above 65(ish) the truck vibrates. The worst of this is during the transition between 'under power' and 'coasting'. Like, if I let off the gas to coast it'll hit that spot real fast where it's not quite doing either, and it shakes the truck like crazy. If I hold the pedal just right, right at that spot, it'll keep doing it. If I pop it into neutral and coast, it does it real bad, too. If I power back up, it settles a bit, and if I stay in deceleration, it settles a bit. It still shakes at high speeds, but that particular shudder is the WORST.

Things I've done to try and remedy:

Front end (u joints, tie rods, drag link, kingpins)
Tires
Motor mounts
Tranny Mount
Different Tranny
Rebuilt TC
New u joints on the way back
New driveshaft
Different flywheel
Different clutch

It's driving me nuts. Basically, the engine is original, the rear end is original, the transfer case has the original shafts in it, but other than that, everything has been replaced and it's still there.

Any thoughts on that one?

[turbovanman²]

Measure drive shaft angles, use a cheap magnetic inclineometer. Get the driveshaft balanced. Is it a 2 piece with a steady bearing? If yes, check/replace the bearing too.

[black86glhs]

Have you verified one of the axle shafts aren't bent? Also, have you replaced the track bar(or whatever it is called). I had a mid 90's model with a bad track bar that caused the exact same thing.

[Subliminal]

Well I got the pinion angle under control by redoing my crossmember and i found that the rear yoke was a little loose and when I tightened that up (along with the crossmember fix) it really seemed to help out quite a bit... Still have some stuff to sort out, but I think I'm on the right track.
:-)

[turbovanman²]

Well I got the pinion angle under control by redoing my crossmember and i found that the rear yoke was a little loose and when I tightened that up (along with the crossmember fix) it really seemed to help out quite a bit... Still have some stuff to sort out, but I think I'm on the right track.
:-)

You should get the rear preload set correctly, if it was loose and you simply tightened it up, that can be very bad as there is a crush sleeve back there, the preload needs setting correctly otherwise boom. I would also take it apart and inspect the pinion bearings, they could be worn.

[Subliminal]

Sorry, I meant the rear yoke on the transfer case... Haven't messed with the rear at all.

[5sp. mini]

is the front u joint free no frozen up might be why transfer case joint loosed up?