123 Trans problems HELP!

[MBBOB]

I replaced the trans in my 82 300D with anexcellent trans from a rusted 300SD I had. Changed the rear housing and spedo pick up along with filter and Mobile synthetic fluid.

Initial start up was good with some harsh early shifts. I drove it around the neighborhood 4-5 different times tweaking shift pionts until all was perfect.

I took it on the first road trip +/- 80 miles on turnpike with 5-10 miles around town that day starting and stopping several different places, all was well. I went to leave at the end of the day and when i started it it immediately began short shifting. 1-2 in 20 feet, in 4th in 100 feet.
I had to manual shift all the way home. Manual shifts are crisp, and in 4th on turnpike worked flawless.

Checked the following:
1) vaccum from pump 15" at idle 20"+ at throttle
2) modulator holds vacuum at least 30 min
3) proportioning valve on IP to modulator, 10" at idle, drops to 0" at throttle
4) adjusted shift cable to extremes with no change

the only thing I can think of is something changed or stuck from when I shut it off and then started again

Any ideas out there? where should I start looking?

Thanks