When the GC is put into reverse the van backs up about 5 ft. and then gives a nice jerk and clunk. It will keep going back without any trouble but it is very disconcerning. I know there is a problem but can't imagine what it might be.
There is no check engine light.
More info: 3.8 engine, 4 wheel drive.

 

I am having the same situation although I was initially blaming it on the inner CV joint. I haven't gotten around to debugging it yet, but I have also noted that the clunk only occurs when I apply the brakes as I back up. Will yours clunk if you just back up without using the brakes? I'm now suspecting my issue is something loose and shifting, or a pad moving in the caliper.

 

Have you checked your drive shaft u-joints?

 

Ck the axle nuts on the drive axles, they sometime come loose, not to come apart. Just to make clunk sound. The nut size is 1 1/4. torque is 160 to 220 foot pound.

 

Thanks for the replies. I finaly got around to following up on this. My wife mostly drives the car so I keep forgetting about it.
I checked the ujoints and axle nuts. They are both fine.
Any more ideas? There does seem to be quite a bit of play between the tire on the left side and the one on the right side seems like you can turn one tire several degrees before the differential catches. Is that normal?

 

I'm still chasing this same problem! I did thighten both axle shaft nuts, and although I tightened them up quite a bit, the problem continues. It is quite disconcerting and almost feels like it may be the differential. Without someone to try to see any movement when it clunks, I'm at a bit of a loss. It only happens when I use the brakes in reverse. It will repeat 2 or 3 times as I back up and apply the brakes.

 

Check the condition of the front and rear mounts.

 

Nexttopool, Is your van a 4WD model?

 

No it isn't. I'm still thinking it is the RH brake or ball joint since it only occurs when I put on the brakes--all of the torque reaction is between the tire and knuckle asm. Although my engine mounts are fine, it isn't related to engine torque. I'll find it one of these days when I get a helper to lay under it while I back up

 

I am getting something similar in my 2005. It will sometimes occur after I have to a complete stop when going forward as well. I still have not found my problem, but I wonder if it is vacuum related since it only happens when the brakes are applied. Perhaps the master cylinder is leaking? Now that I am thinking it through, I doubt if that is the problem because I do not lose any pedal pressure, but I will still throw the idea out there to get others thinking.