My '98 disco has 93k miles. This is a one owner truck in very good condition that we have had for about 10k miles. Yesterday it developed a loud hard clunk on upshift only. First it was 1-2, then , 2-3. No previous P-R clunks or anything. Trans fluid was clean and at the right level. No slop in drive train at the u-joints. Noise seems to be center transfer case, not either diff.

Any ideas?

 

I would check the t-case fluid condition/level. As far as the u-joints, to check properly, you have to remove one end of the drive shaft, and wiggle the joints looking for slop or binding. I used to not believe this until I had both rear u-joints going bad, checked by rotating looking for play. Looked good, the as soon as one end was unbolted, you could definitly see they were bad.

 

I had this problem; for a quick fix rather than replacing all the massive problems. First, try Lucas Oil Transmission Stop Leak, it helps "clunking" greatly. I had similar problems.

 

The timing of this shift can cause a momentary torque reversal of the output shaft that results in a clunk noise. This condition may be worse on a 4-wheel drive vehicle due to the additional tolerances in the transfer case. Replacing the rear drive shaft has solved alot of clunking problems. The slip yoke is the culprit.

 

I had a post a little while back about harsh shift. Turned out my kick down cable was to blame. That is the easiest thing to check first. Look at the throttle body end and see what condition the cable is in. See if it came apart or is just out of adjustment.

I rattled around all of these ideas and after I reaffixed my cable correctly it has shifted the best it ever has. Good luck and keep us updated.