I've decided that this isn't my imagination. When driving the truck drives and shifts smoothly. When you come to a stop after a few seconds there is a very slight thunk sound that can be heard if you are paying attention. It doesn't seem to happen right away after I stop and sometimes it takes longer than others. It sounds like something might be disengaging or something. Anybody have any ideas what it might be? The truck was just at the dealer for the belated 90 check up. I assume they checked for codes.

Don't know about the newer trucks, but with my 93 with rear ABS, it clunks once in a while especially at a quick stop. From what I'm told it's normal with this ABS system.
Hope it helps.
Mark

Lube the slip splines on the rear driveshaft with a good synthetic grease. This is a common complaint on JEEP's and some other various trucks. The slip splines will get bound from being engaged and when you stop the splines are bound and the clunk you hear is the splines unbinding. Normally a high quality synthetic grease will take care of it, on the JEEP's they found that swapping out the slips for nickel plated ones solved it.