It's quite possible this problem isn't transmission related, but that is my best guess at the moment. I'm wide open to any other suggestions.

I'm not normally a diesel guy but bought this as my daily thrash because of it's history, condition & because it has an interesting engine, a DOHC 5 cylinder, 4 valve, intercooled turbo which has surprisingly sprightly performance & pretty good economy. It also runs quite happily on veg oil. Unfortunately, I think the 722.612 5 speed auto transmission is starting to act up.

Occasionally it feels like it's trying to pull away from a stop in much too high a gear. It makes no difference if I manually shift to 1st or 2nd or any other gear, it still pulls away very sluggishly. If I move the shifter up to P & then back into D it will select the correct, lower gear & pull away as it should.

Also, occasionally after brisk acceleration it will hang onto a lower gear far too long & be reluctant to change up after I've eased off the accelerator or even taken my foot off it completely & coasted.

Had it on a Star & there are no g/b or engine faults showing, ATF level was good. ATF was changed in July '07, 42K miles ago, when a new transmission control unit (026 545 91 32) was also installed, all at an MB dealer. The car has 124K on the clock now.

This is a car with full history & every receipt from day one (including factory collection paperwork) that I bought from the original owner, a wealthy, retired 70-ish year old who looked after it properly & never abused it. TBH I'm no longer sure whether it's a gearbox issue or an engine one. Might even be something neither I nor the MB independent who Star'ed it have thought of.

Anybody got any idea what the problem could be? I'd welcome any suggestions or help.

TIA.

Conductor plate, TCM (already replaced), likely culprits. My 97, same trans, did the same thing years ago, went through 2 TCMs and 2 conductor plates before 200k (Thanks MB CPO!). Although, I would do a trans change (don't forget torque converter!) every 30 with MB-approved fluid on these versions. There should be some codes that direct you to the immediate, offending culprit.

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former: 83 300D, 97 C230, 93 400E

current: 08 C300 Luxury , 92 500SL

Will, thanks for that.

The problem is there are no codes or faults showing up! The transmission module the PO replaced in '07 cost about GB£600 (roughly USD$900) installed so problem solving by guessing on this is out of the question.

I'm stumped as to what it could be that would cause the problem but not show up on Star.