W116, Body and Interior Specific Aid

I am about to fix a 1976 300D that does not change over to heat when you turn the A/C off. We bought it from a dealer and know very little of the car's maintenance/repair history. I can tell that the car was well maintained and runs/drives great. The heater slide controls are working, but whatever is supposed to happen when you turn the A/C knob fully counter clockwise is not functioning. I was wondering if anybody knew of a common problem that I should look for when I repairing this.

While driving, the trany shifted to nuetral by itself. No position on the gear shift changes the condition. However, when I shift to park I do get a grinding noise before the gears mesh. Every other position is quiet. I was told that I may have to replace the transmission and I am willing to do so as long as a second opinion agrees with the first.

If I do need to replace the transmission, I need a good manual to help out.

At any altitude above 3000 feet my car's transmission shifts roughly, sometimes refuses to get out of second and when it does, will not go into fourth. I discovered this yesterday while on a trip up to Lake Tahoe- did not make for a pleasant experience as one might imagine. Is there a Barometric switch anywhere in the system that might have gone erk, or is there some other problem that might be the culprit? The Trans shifts normally here in the valley, if that's a help.

1986 300 sdl,"RennPanzer", 284K miles

I have an '81, 300SD, that sat in a field for 2 years due to leaking engine oil cooler lines. Replaced lines, checked all fluids, started and ran, and then took it for first test drive. Noticed it was slow going into reverse. Have zero (0) power to power-brake booster. Figured vacuum pump needs to be either replaced or rebuilt. As I checked the transmission fluid, with the engine running and the transmission in park, when I checked the fluid it seems to be over-full. Previous owner was adding Dextron/Mercon trans fluid. As I put it into reverse it is taking longer and longer each time for the reverse to engage. Are the above my problems, ie: vacuum, wrong trans fluid, improper checking technique, or is the transmission going south?