testing for transmission slip

[tmsbandman]

Yep. that's what I did, but at about 50. I've got some kind of "chunk" when starting off. U joints seem fine. Maybe clutch packs in differential?

[Longshot270]

Is your truck lifted? I've heard that often times the drive shaft will make a clunk as angles change under load.

Do you also have anything loose in the cab, toolbox or bed? My truck makes a clunk when I accelerate but it is from a bicycle seat post rolling into the tailgate.

[tmsbandman]

Nah. It's completely stock other than Gotts mod and some cosmetic stuff (rims, chrome).

Nothing at all in bed. It almost feels like my rear calipers are hanging up, but they don't seem to be wearing prematurely. Wonder if it would help to take the caliper pins out and lube them. I've already replaced the front calipers (early model '04) but I don't think there was a design flaw with the rears. I didn't see a TSB about them.