87 300D One Click
 

I have been doing maintenance/repair items, getting my car ready to be my daily driver. When I put the car in drive and after I take my foot off the brake and the car starts to move forward I hear one click. It does not do it in reverse only, in drive. The click sounds like it is coming from the transmission area of the car. I checked the rear flex disc the other day, it looks very good. No distortion or cracks. I was not able to check the front one.
This weekend I am dropping the subframe to install new mounts, spring links, sway bar links and the diff. bushings. When I get the car in the air I will have someone put the car in gear and see If I can get it to CLICK.
Could it be the transmission mount? Engine mounts look fairly new.

I'd look into the motor mounts.