I have 376k on my 87 300TD, 280k on my 87 300SDL, and 200k on my 92 400E, all original trannys, and fluid changed but not that often even, maybe every 50k miles.

I had an 83 300TD that broke the B2(?) piston at 215k, and the clutches were getting weak (long delays from fwd to reverse and back) but it still kept on after piston replacement. They just keep on runnin'

Gerry