I'm posting this up on behalf of my dad. He has a '93 6.2 with the 5-speed stick. When he lifts the clutch up coming out of a dead stop or near to it, the whole truck shutters and then gets going. Happens no matter how easy up let up on the clutch. Any thoughts as to what's causing this? I'm sure that the clutch isn't slipping, so anything else to check off the top of your head?

Thanks

So the clutch is chattering, not slipping. As I recall this can be caused by oil on the clutch (but it's late and I'm very tired so I might be way off). You might be able to spray the clutch down with brake cleaner and dry it out, but you might have to replace the clutch. Don't replace the clutch without diagnosing what is causing the chattering because it will do the same thing to the new clutch if you don't.

Sounds like you have a broken spring or springs in the pressure plate or clutch disc. Other cause's may be hot spots on the flywheel or the face of the pressure plate. When you replace the clutch make sure you resurface the flywheel and replace both brg's That sound fix the problem the sooner you repair it the better very hard on the drive line