metallic clank when shift from 2-1
 

Yesterday I put in a new motor mount in my '83 300SD, and also checked the valve adjustments. Today when I slow down and the tranny shifts fom second to first, there is a loud "clang." What gives? Could I have misallaigned something when I jacked up the motor to get the new mount in there? The car has 193,000k and was shifting perfectly until today.

Check you tranny mount (rear motor mount) and flex disk. Both can cause a clank/clunk.

I know where the tranny mount is--what about the flex disk?

I also checked the fluid level, which before putting in the new motor mount was right between the two lines--now it is overfilled. Could installing the new mount and raising the motor have changed the ATF level?

probably a vacuum connection not reconnected properly
 

My guess is one of the vacuum lines got disconnected. It wasn't noticeable in the test drive was it? Is it only between 1 and 2?

I think checking the ATF is supposed to be with the tran at operating temp with the engine in park and idling. It can be hard to read correctly.

The flex disk is the coupler between the tranny yoke and driveshaft, a large hard rubber disk mounted with 6 bolts. Look at it closely using a bright light if necessary to check for any cracking or tearing. Grab the driveshaft and try to rotate it...it should be rock solid with virtually no movement. If you dectect movement try to watch and see if the tranny yoke is moving in unison. If yoke remains stationary but the shaft is moving that is a good sign the disk has taken a trip south. Best to replace before they destruct because the driveshaft will destroy the hump, the tranny, the crossmember and a few other items.