Good evening!
Have reviewed various threads but can't find the same problem. About a month ago while backing into a parking space and shifting into drive to straighten out, my '89 560sel drivetrain seemed to "pulse" forward as though brakes were trying to keep car from moving. Backed up into space and parked. After work, car started and drove fine. A few days later, same thing happened. Checked brakes, changed differential fluid and checked transmission oil level. Three days ago, noticed 2/3 and 3/4 shifting was intermittent after warm up. The next day, 2/3 and 3/4 shifting were non existent. Checked Bowden cable and removed kickdown cable with no change. Removed vacuum line from modulator and 2/3 and 3/4 shifting returned, albeit rather harsh. Ordered new modulator. Yesterday, while backing up to park, drive train again pulses and transmission exhibits the following: reverse is ok, neutral is reverse, forward gears seem to be opposing a reverse mode (no forward motion) and park is park but engine still seems to be loaded in reverse mode.
Changed oil, filter and modulator with no improvement.
This is my second 560 in good condition with 220k. I have pulled several transmissions and replaced with recycled units only to pull them again to replace primary pump pistons, some springs and a front bushing, etc. As the current symptoms don't include crunching noises, leaking oil or metal bits in the pan, I am seeking DIY diagnostic advice before pulling yet another unit (outdoors). I have a spare "parts" 722.3xx to practice with. Any help will be greatly appreciated.

I will pull the transmission this weekend and will open it and report what I find. As simply replacing the broken parts in a hi mile (220k) unit is not as dependable as a complete rebuild and the learning curve is too long for my daily driver, I have decided to purchase a rebuilt unit out of north Jersey. The next time around I will be better prepared.