83' 300 Turbo D. doing the same thing
My 83' 300D turbo with 146K does the same thing. I don't think that it is slipping and believe the proper terminology would be it is flaring. Mine will not change gears without it first increasing RPM, and then you get a neck jerking change. If it slips, RPM will slowly increase and a delay (which seem to take forever)with no pulling power is experienced while the tranny is trying to change gear. I have found that there a few adjustments which can be made at the tranny modulation valve and a cable which is connected to the throttle on top of the engine can make a big difference on the shifting pattern. I found the information under search with key works like (tranny, no shifting, transmission problems). If your problem has just started, is your vacuum system still working correctly. Vacuum loss is a big thing to these trannys.