[Hi Volt]

I have had this issue occasionally and have come across apparent different causes, at least the symptoms always felt very similar. The thump in the butt feel upon stopping and the occasional thump on starting off can be caused by the rear-most u-joint starting to go bad. I have had this issue twice before and it has always gone away after the change. Recently I noticed it again, and very regular, and again assuming it was a u-joint issue again did the routine change. Upon inspection I did notice some very light needle bearing impressions in the journals, but not as bad a previous times ( comes from hard driving ). These impression will cause binding in the joint under load ( not noticeable if the u-joint is articulated by hand ). Well after the re+re the problem still persisted which was very discouraging and annoying. I started to think it may be a brake issue so I did a simple test. I first placed the park brake on 1 click and went for a drive, this has the effect of tightening up the brake adjustment a little. ( note: The closer the pads are to the drums the less fluid is required to move them the rest of the way and the more responsive the brakes feel ( as they actually are ). Rear brakes use return springs to pull the shoes back from the drums, however as the shoes wear this gap gets larger. Disc brakes on the other hand always maintain light contact when released so they always stay adjusted.)

Anyway, there wasn't enough improvement to be conclusive so I did the same test with 2 clicks and then 3. With the brake on 3 clicks the problem was gone and the brakes also had more grab, but were not dragging. My rear brakes were in need of adjustment as it took about 5 clicks before I could feel drag while driving. Regular use of the park brake is supposed to adjust the rear brakes but it doesn't do as good a job as a real "hands on" brake adjustment in my opinion. I usually keep my rear brakes adjusted because the brakes simply work so much better and the fronts won't warp, but I guess it just got away from me this time. Anyway they are adjusted now and problem gone.

So within a few minutes you can do the park brake test I did and see if that helps, if so, crawl under and do a proper brake adjustment (or service if you are due).

Hope this helps out

P.S. Here is an adjustment tip I use - When doing the adjustment there is a distincive "ting" noise after each click ( noise through the backing plate ). Listen carefully for a pitch change to a destinctive deeper "tong" sound. This is the point I stop the adjustment and it seems good. I prefer this to trying to feel for the same amount of drag side to side by spinning the wheels ( a method I used to use).