Transmission hits hard??
 

1990 300E 2.6 The car seems to really hold onto first for a long time, shifts into 2nd with a hard hit, then quickly to 3rd. It doesn't always do this, normally under heavy acceleration. I know the shifts are harder when you put your foot into it but this is borderline painful in the car. Any ideas? Would a filter/fluid change help or does it seem worse?

Sounds like the "warm-up" up shift delay is working all of the time.

There is a solenoid at the front of the trans on the drivers side, try unplugging that solenoid & see if the trans acts better.

I will give that a shot, thanks!