1982 123 300D Trans slipping.
 

Trans suddenly started slipping. Takes a Lot of acceleration to get to move. Before I parked it, it seemed like if I could get it going up to speed it seemed almost normal. Slips no matter where I place the shifter, even reverse, but will move. Car has about 190,000 been driving it since about 160,000. I read up on B2 issues and pulled the pan. Trans seems very clean, zero metal and normal fluid color, no smell. Pan was so clean it must have been changed before I bought it. I have read that if slipping in both forward and reverse gears while manually shifting that trans is shot and not really clear from my research if B2 affects reverse. Only problems since purchase was bad 1-2 or possibly 2-3 flare (these trans shifting confuse me), assuming you start in first, it seemed liked you felt a "little" shift almost immediately, so flare came later, must be 2-3, so I mostly manually shifted the low gears to avoid the flare. I went ahead and put in a new filter and cleaned the pan again, but have not refilled with fluid yet. It has sat for several months, but just did the filter last night. Decided not to fill until I got some feed back and maybe needed to check in pan again. No B2 rod in pan or anything obvious and my B2 externally has zero access. Any ideas?

Two thoughts:

1) The B2 has nothing to do with forward [EDIT -- has nothing to do with reverse :P] motion.
2) You might want to post in Diesel Discussion -- that is actually the place to go to for help with diesels (Tech Help is for gassers). Diesels make too much sense for 95% of those here in Tech Help to know anything about them :D.

Try this unhook modutor line to mod. Vavle under or on top .pull line off No vacuum drive car it willshift out very very late.but if it shifts firm it not a trans problem. Plug out vacuum modulator again.pull off black cap rubber cap.u will see a tee pull it off just enough to turn it iN 3 full turns in drive it lmk pm me

Assuming you have a 722.315 fitted =>

Make sure you've drained the torque converter and then measure in 6.11 litres of dexron II ATF.

Take a look at that volume figure - point one one! It might seem a little bit anal not to just say 6 litres but you need to make sure that you know exactly how much fluid is in the transmission. This is really important. Measuring the volume with a graduated measuring cup is what is needed for this - do not "use the force" and judge the level by eye on the marks on the outside of the bottle.

After filling with ATF do not race the engine - give it some time - just imagine the front pump pumping all the good stuff round the transmission for a bit...

...check and adjust your throttle linkages and the linkage to the Bowden cable. Check your vacuum system.

If that doesn't do it report back.