I just bought an 83 300TD with 199,xxx miles on it. It starts and runs well, getting up to speed well, but sometimes the engine revs between shifts, like it's not wanting to engage the next gear. Also, when you apply reverse from park, there is a pretty good delay before you feel it engage. Finally, it suffers from a lumpy idle, sometimes making odd thumps, like a misfire in a gasser would sound and feel like.

It starts immediately, even after sitting a week or more, and smokes only slightly on cold start after sitting a bit, once warm the exhaust exhibits no visible smoke at idle, if revved there's a small hardly noticeable puff of black, I can see no smoke when driving no matter how hard I load the engine.

Potentially relevant known issues:
1) air cleaner was just rattling loosely attached to the turbo, this have been corrected with new bracket, rubber bushings, heat shields, and rubber seals on the U shaped plastic pipe at both the air cleaner and the turbo, so it is tight now but who knows how long it was run this way.
2) The primary filter, looks nothing like the ones I see in pictures. It's not clear, and it appears to be the small brass type thing, it's very odd. I have not idea, when the fuel filters were changed. The primer pump has this strange plastic thing on top the looks like a big hex nut.
3) the engine mounts are obviously crushed to ruin, the engine actually appears low in the bay, and appears slight out of line (not perfectly straight nose to firewall).
4) the temp gauge seems to run right at what looks to be 90 C, and climbs to what appears to be 100-110 C, when loaded on a long grade. Both seem high to me. When coasting down a hill, the temp drops to just above the 80 C mark.

Any insight much appreciated.