85 300D rear end clunk on low speed downshift
 

I get a severe clunk at the rear endat low speed, power off, downshifts (coming to a stop) and at power on, accelerate hard downshifts. I think I have the vacuum curve within specs going to the transmission modulator and the vacuum modulator itself has been replaced. I have also adjusted the Bowden cable to eliminate 3/4 geartransmission shift flair. This car had the clunkproblem when I bought it,but I knew it is commonly eliminated or reduced by resoving vacuum problems, soitdidn'tconcern me too much at the time. I have not, however,been able to eliminate the clunk even though vacuum issues have been addressed. I haveeven triedblocking thewhole vacuum circuit to the cabin to eliminate any possible leaks or odd vacuum behaviorfrom there effecting the vacuum curve to the modulator.The car has a relatively low 137,000 miles on it, and the diff. fluid level is fine. Does anyone know of a problem in the differential itself or elsewhere in the drive trainthat can cause this behavor?

RE: 85 300D rear end clunk on low speed downshift
 

This is a complete guess but it could be a bad flex disk they do go bad over time and it cant ever hurt to replace then. If you can DIY it should be a cheap thing todo.

RE: 85 300D rear end clunk on low speed downshift
 

Thanks for the reply and the suggestion to check the flex discs. I have had them replaced and the transmission mount also.Has anyone ever heard ofold softmotor mounts causing rear end clunkwith coming to a stop downshifts? I know the motor mounts are allowing quite a lot of side to side engine movement. Can that lash through the drivetrain and cause the rear end to clunk? If I have the transmission in "S" rather than "D" when coming to a stop I get no clunk. The clunk happensonly whenthe transmissionis in "D" and shifts down from 4th gearwhile rollingto a stop.

RE: 85 300D rear end clunk on low speed downshift
 

Soft motor mounts are common, and could cause the noise you mentioned if they are bad enough. Flex disk would be my best guess. Also, there are some plastic stabilizors (don't know the proper name) on the rear near the shocks, they commonlywear out and make some strange noises.