Hi, I have owned a few older benz diesels, 73,81,82 300D's, loved them all but wanted to try one with a little more power? Anyway this one has 220K runs great.
1. The only problems are under light load the trans shift from 2nd to 3rd has a hesitation and the engine revs up for a second, under full throttle it shifts great? The trans also cannot be shifted down manually with the lever, you have to step on it to get it to shift?
2. The other problem is the AC, the center vents wouldn't open until I went in and helped them stay open, however the AC is cold but I can't get it to stop coming out of the defrost? Any advice would be appreciated, thanks

The best way to deal with the transmission issue is to start with a fresh ATF fluid change and new filter. That can take care of several problems.

On the climate control issues, some of it sounds like it may be vacuum and some might be the climate control module (with all the pushbuttons). The solder connections inside get broken with all the mechanical stress from the pushbuttons and cause a lot of problems.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

Fix the vacuum supply problem. Most likely the transducers for the EGR and air recirc valve are busted and leaking, and the way that system is set up, you won't have enough vac for proper transmission control or ACC.

There is a 5-way T connector at the front of the engine. Check it for integrity, then use a MitiVac to check that all four branches hold vac. If the two on the passenger side do not, you have busted transducers, and can just plug the lines (I did this about 100,000 miles ago) or replace the transducers if you want the EGR and air recirc valve to work.

You can trace the line to the ACC, it goes into the passenger compartment near the brake booster. Check it, it must hold vac unless it is switching modes. Likely there isn't enough vac due to a leak or broken line, easily fixed.

That will restore both tranny control and ACC operation. Note that the dash center vents are ONLY open for high cooling, they close while the side vents still blow cold air.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

1. The transmission on the 87 is supposed to have a little 2-3 shift flare unless its not running properly. It depends on how exaggerated it is, in regarding it to be a problem or not. Sounds fine, unless it really bothers you. Definitely change the ATF and filter regardless.
2. The A/C vent problems can be CCU related or vacuum related. I would replace the vac switch solenoids (or whatever they are called) behind the glovebox, first. Then look into CCU, probably cold solder joints.