front prop shaft shakes like a wet dog.

[heptofite]

i forgot to unlock my hubs the other day and the front prop shaft was shaking so hard it made my pedals vibrate when i was going highway speeds.

there was also oil all over the thing, but it was black, and the front diff oil is literally under 200 miles old, so i don't think it's related.

possible u-joints?

 

[AllanD]

U-joint would be my guess.

If you had a later truck with a 13-54 or an STX I could see it
being the centering ball in the double cardan joint, but since you don't have one of those....

Yeah, check your U-joints.

Better yet, pull the shaft and drive it once with the shaft in
the bed with thehubs locked to rule out some other stuff.

AD