My '92 400E operates similarly. I have received consistant advice with respect to fluid level, quality and age.
I must say however, the "whump" in the rear caused bythe B-2 piston problem concerns me. What exactly is "whump" ?
I have noticed in cold temps when I begin my accent up my street that I get a fairly significant "thud or clunk" from the rear...Is that it ? What about the seal repair that helps minimize the slow shift responses? Are these items that should be handled at one service since I assume both require the tranny to be removed?