1982 300D

Have a few questions on my 300D. For starters I am going to replace the transmission fluid and filter within next week or so but have noticed some things and not sure if they are normal or not and just wanted to check and see if while I have fluid and filter out maybe there is more I should be looking for or do.

First is when I shift from Park into either drive or reverse it seems to take a few seconds before the transmission actually goes into gear. Curious if this could be a vacuum related issue or shifter bushings. Has done this pretty much since I have owned the car just hadn't been to concerned and had more important things to take care of first. Any other ideas would be great.

Second is that when it does go into drive or reverse it seems to kinda jump or shake the car. It doens't clunk or anything. More of a shake of the car. I just replaced the motor mounts and the transmission rear mount. Any other ideas what could be causing this.

Overall the car shifts just fine. Every once in a while when its cold it will flare between 1st and 2nd or 2nd to 3rd. But it doens't do that often and when it does it seems to be more so when I am having a vacuum related issue. Like when I unlock my doors start it and drive and the back locks still havent unlocked or if I have EC selected for heating and its not blowing yet due to lack of vacuum to switch the pods on or whatever it does in there. Sorry probably should be some seperate threads but just looking for some info.

Thanks