1982 123 300D Trans slipping.

[Vox600]

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?