Rear end noise
 

Hi to All,
Well I just got back from a 500 mile trip. Halfway through the trip I noticed, while in town at low speeds, a solid thump from the rear end when the tranny upshifts. It only happens when you back off the throttle after accellerating to a low speed, say 15 MPH. The thump is enough to feel like a bump on the road, but it's not. Anyone have an idea what it could be?
Thanks, Brian

Our '83 does the same thing, if you don't let up on the accelerator (enough to keep tension on the driveline during the shifts) then it is clunk-less, but letting off completely it will make a clunk upon shifting. On ours I traced it to play in the differential...it has quite a bit, in neutral you can turn the shaft around 1/3 a rotation almost before it "catches" the output to the wheels. At 258k the diff (probably neglected anyways) is just somewhat worn out so the gears have play, it drives fine and doesn't whirr much, but it just has that play in it, not much can be done short of replacing the differential. I'm going to change the fluid in both of ours soon as a precaution/maintenance measure. Maybe it will cut down on the whirring. Mine doesn't clunk or whirr at all, much tighter...

i had the same problem. i have an extremely worn differential as well. however, after changing the tranny and diff. fluids, i haven't noticed the problem anymore. i used mobil 1 atf for tranny and that thick lucas stuff for the diff.

You live in a nice hot place. Why not replace the differential lube with a synthetic 75W140 weight? Like this one from Redline http://www.redlineoil.com/products_gearlubricants.asp?pvID=106&prodID=60&subcatID=20 Still being synthetic it will have enough viscosity at low temps to flow well yet be thick enough to cushion some of that impact on the gears from the slop in the diff. Just a thought... RT