MR500SEL

my 84 500 SEL has 105K on it. The trans makes a "thunk" sound down shifting when I take my foot off the gas. I had always thought it was normal, but another w126 owner suggested that it was not. He thought it may be something to do with fluid presure and may be fixed without tearing out the trans. Anyone have any thoughts on this?

m117968

are you Sure it's the trans and not coming from the rear? Could be worn out half shafts or diff..
But, it could be the transmission as well. Does the car shift normally otherwise?

Jonathan

MR500SEL

I does seem to come from the rear now that you mention it. The car shifts normally as long as I am on the gas, but as soon as I back off the gas the shifts (up and down) have a pronounced "thunk".

m117968

I would get the car up in the air, check the flex discs, rotate the rear wheels back and forth...see how much play is in the diff..should be negligable to none. If you can Feel it, your half shafts or diff are getting tired. By gently rocking back and forth you should be able to tell if it's shafts or diff.

Jonathan

MR500SEL

Thanks!
I will try and get it in the air later this week. I have noticed, however, that there is movement after I stop the car and place it in park. Interestingly, if I put the car in park (on a level surface) from drive, and turn off the ignition it will roll forward a few inches. If I do the same thing, but move it from reverse to park it rolls backward a few inches. Could this be related?

Also -- how much does a repair to the half shafts or differential run?

m117968

Well, to start, you should be engaging your parking break before you put the car in park, rocking onto the pin doesn't do it any favours. But they all will rock w/o the brake engaged. You pay for what you get w/ half shafts so at least a couple hundred a side, as well as a few hours+ to R&R. Diff work will depend on how tired it is, but generally it's not cheap.

Jonathan