My '94 E320 has a problem in which the transmission sometimes tries to upshift, but then shifts down and then finally up. This is under moderate acceleration. It's like the car wants to shift to 4th and does for a second, then kicks down to 3rd abprutly and then goes back to 4th.

I am planning to change the transmission fluid and filter. Did these cars come with synthetic stock? I was going to use M1 synthetic since I've had good results with it in my Volvos.

Thanks,
Dave