Recently developed a rear end thump. It seems to happen when I take off from a stop when I put the foot into it. A few times getting on the highway it would give three or four short thumps in a row and I'd let off the gas for a second and it went away. Any thoughts? U-joints? Tranny? Anyone experience this?

I have the same problem. I have a clunk when stopping or taking off. Does anyone have any info on it?

I had my mechanic check out the problem yesterday. He raised the van and checked the U-Joints, all was well. We took it for a test drive and the speedometer started jumping around again. (I just had this speed sensor at the crankcase replaced at the dealership in May) ,,, anyway, the thump in the rear end was noticeable every time the speedometer jumped, it is jumping around to the point where it feels like it is in neutral and then catches back up to speed (that's when it hit the back end hard) ,,,, My mechanic says there's a sensor at the back of speedometer and I should get one and he'll replace it ,,, said he just repaired this same problem on a Nissan.

Can anyone tell me if there is a sensor there? what it's called? or if you've ever heard of such a thing?

Anyone got a manual for 1997 Astro AWD? If you do, can you take a look for me?