Klunk when downshifting

[WALoeIII]

I've got very quiet clunk that I get when downshifting. This only happens when shifting OUT of second when engine breaking, it doesn't happen from 4th or 3rd. If I engine break with 2nd a little, (not really even engine breaking too, I can just leave the clutch out and break to slow down and then not release the clutch until engine is at ~1000 RPMs) there is a klunk when shifting out, like the transmission is moving or something. Suggestions for things to check, any thing I should do/test to give you guys more information?

 

[lowtideride]

bad u-joint?

 

[WALoeIII]

Why does it always happen when shifting? How would I check my U-Joint?

 

[lowtideride]

a bad u-joint will also clunk when braking hard in reverse.. you can climb under and grab the driveshaft with two hands and twist back and forth. check both u-joints in the rear when ya do it too.

 

[lowtideride]

might also be slop in the rear diff

 

[WALoeIII]

Ok a little update on this. If I switch between 1st and 2nd while coasting slowly (~5 mph) I get the clunk both ways, as soon as the truck stops moving it goes away, this only happens between these two gears.

 

[lowtideride]

still sounds like what was said above...just replace the u-joints...they are prob bad/old anyway.

 

[WALoeIII]

I went under the truck and turned the rear drive shaft, it seems like the slop is in the rear diff, not in the u-joints. Ring/pinion?

 

[cruiser_guy]

You MIGHT be able to take up the slack just by re-torquing the rear pinion nut (I was able to). You will want to replace or keep an eye on the seal there as well (I had to replace mine). If you can't take up the slack you'll need new bearings for the pinion.