I just picked up a high mileage (317k) '83 300DT and have been going through the car fixing typical problems (dash lights / door locks / etc.). The car has a strange shifting problem that I haven't seen before... I haven't found any similar problem using a search (though I'm not sure if there are better keywords to use).

The car will sometimes buck back and forth between 2nd and 3rd. It kind of hangs around 3000rpm and revs up/down like it is thinking about shifting. If I let up off the accelerator it will shift and I can continue driving. Otherwise it seems to shift pretty well (though it sometimes revs just a bit before it catches first gear).

I've been trying to troubleshoot the tranny vacuum system and haven't found anything obvious (though I'm still a rookie this). Any tips for me on this one? Kickdown cable?? One more question... the car had a serious vacuum leak in the door lock circuit. Can this affect shifting? I isolated the problem and plugged the trouble area last night (until I can fix it properly) but the shifting problem still exists.

Thanks for any help!

-John

__________________
1985 MBZ 300DT
1969 MBZ 220d
1984 MBZ 300TDT
1981 VW Vanagon