I've noticed on a couple occasions recently that my 1985 300D (250k miles) slips when starting in first gear (shift position 'D') from stationary.

Both times the car was cold (60F ambient), and the slippage seamed to go away as the car warmed.

The tranny fluid & vacuum system are good.

Any suggestions on what could be causing this?

Please be more descriptive of the problem. What exactly happens when you say it is slipping in first.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

And what did you do to check the vacuum system?

b2 band valve...easy to do...research it
steve

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85 300d in progress

When my Car started doing that in a Cold Snap here in CA it apparently was the prelude to a B2 Piston breaking.
I changed the Fluid and Filter and the Symptoms pretty much went away till not quiet 1 year later the B2 Piston Broke.

Verify that the B2 piston is actually broken or binding (you will see marks on it) before ordering parts.
Looked like B2 Piston Issue but instead it was a broke B2 Band.
http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1644523-b2-piston-replacement-85-cali-300d-2.html#post5189768

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84 300D, 82 Volvo 244Gl Diesel

It appears that Jr. wasn't clear on how to check tranny fluid level, & car was actually a quart low. Hopefully problem is solved. If not, I know where to look next. Thanks for the info/links.