First of I would like to say hello to everyone and introduce myself as a new member. I don't know how to add the signiture with all my info so I am sorry about that. My question is reguarding my 1993 4x4 250. when I go from reverse to 2nd gear, like bcking out of a parking space, I get an audible clunk often before power is even transfered to the drive wheels. Driveshaft and u jounts seem okay and it feels more like it is from the transfer or tranny. Truck has 140k miles and never towed over 8000#. Thanks for any thoughts.

 

Im going to throw out U-Joint first

 

I thought the same but the driveshaft feels tight when truck is on flat ground with no load and p brake enguaged in neutral.

 

go on and drop the drive line you will be surprised. sometimes the u-joints get real tight before they go

 

I will do that tomorrow when i can get parts. Thanks for the tips. hope it works

 

I'm betting on the diff cross shaft (open) or diff clutches (LSD).

 

how do i check these? Changed both u-joints on rear drive shaft and did not make a difference.

 

With the wheels chocked and the trans in neutral, crawl under the truck and rotate the axle yoke by hand. If you have more than about 1/8 turn of slack inside the axle (and the rear does not howl while driving) then the problem is inside the differential. Pop the rear cover off the axle and repeat the test, you will see where the trouble lies. Open rears have a single cross pin, the spider gears wear into the shaft (somebody posted a pic of theirs worn halfway through) causing slack inside the diff. On limited slip diffs, the clutch packs set the tooth engagement depth between the spiders and side gears. When the clutch packs wear too thin, the spiders and side gears only mesh out at the tips of the teeth - again causing slack in the diff.

 

thanks i'll check that this weekend.

 

good advice from wannadiesel. With an open diff excessive wheelspin (one tire fire) will cause the pinion gears to wear into the crosspin shaft, if it gets hot enough they can actually weld themselves to the shaft and break the cross pin. This can also happen with a wore out limited slip (trac lok style). With a diff this large it would take a lot of wheelspin