My 2000 had an engine replacement done about a year ago-- 4.0 to the 4.6 and the drive shaft was replaced at the same time, I'm told. It certainly looks pretty dang new. Anyway, I can't find any play in it, but when accelerating, particularly at low speeds, there's a pretty decent vibration. If feels like it's coming from the front end, but we all know how that goes. When I let off the pedal, it goes away. Would you advise just replacing the drive shaft anyway? Possible rear rotoflex? I just replaced the front hub assemblies and that corrected the Three Amigos. I was kinda hoping it would fix this, too.

If I replace the front drive shaft, anything else I should do down there while I'm at it? I am going to replace diff fluid while I'm at it.

 

If you have the center diff lock on your truck you can simply lock the center diff and remove the front drive shaft. If the vibration persists that drive shaft is not the source of the vibration. Obviously you can do the same with the rear.

 

Crap! I forgot about that! Thanks!!!

 

Front D/S could be out of balance - I had a similar issue with mine, but the vibrations didn't present themselves until 75mph. Swapped the driveshaft last week and can go up to about 80 before a (presumably different) vibration kicks in.

If you're going to be pulling the front driveshaft, I'd consider a wobble extension and possibly the Lucky 8 tool. Everything on the bottom of my truck is held together with rust. Without a wobble extension and the tool (which I think is supposed to be thinner walled), I ended up spending a few hours down there just trying to get the sockets/wrenches onto the rusty bolts and nuts. Should have been a much quicker job...

Also AFAIK the nuts used on the driveshaft are single-use. You can pick up a new package of hardware for $10 from Lucky 8 if you message them.

 

Thanks! I am absolutely going to keep that in mind!!!