Speedo quit and Tranny won't shift, FIXED IT I HOPE
 

My daughter is now driving my 85 380SE. She say's that the she left a stop light and the speedodometer did not work and the tranmission would not shift. Wife drove the car home she says it shifts into 2nd but no futher. Before this the trany has been very good. I replaced the vacum modulator because it leaked vacum. I adjusted it by how it shiffted not by the meter method that I researched. The modulator has been on for 6 or 8 months. It has not gone into reverse or park a couple of times. but not for along time.
I have not driven it yet will be home Thursday to see for my self. Any help or insight would help. Alan

There is a switch under the carpet / accelerator petal
Unplug it and see if it corrects the problem

New Info Would help me
 

Well I got to see the car. When I got in it, it shifted ok. So I decided to increase the pressure on the vacum mod. I replaced it about 5k miles ago. It helped the shift points very much. So I drove the car for about 50 miles in town, stop and go to see how she would do. All great until leaving one light it shifted to second then no more. I have come to the conclusion that the bowden cable I think they call it is sticking. I did take off fast and this seems to make since to me. Then it came to life again but the shift points where off and as per researching this cable also controls shift points. Another one though when I went to park it in my drive the shifter would not go past neutral put back in drive moved car a couple feet then it went in park. Guess I will research more. Thanks for this forum, I don't think i would play in the gas MB's if it was not for your guys HELP.

I would listen to brabus.

Going outside right now to try this. Also the speedo does work.

Well I tried the switch, went well car shifted fine drove the car about 2 miles. As I came to the last stop sign and made my left turn it was like it was in neutral. Then as RPM went up it sliped into gear. It still was slipping in and out as if no oil is getting to the pump. So being discusted I parked it and came in out of the cold. It is full of oil. Will look at it on a better weather day. Will search for threads like this. It also would not go into reverse or park. And I know the linkage outside is good and tight no kinks. This car is almost in perfect condition till this. 164K on speedo.

When was transmission last serviced (i.e. fluid changed)? Check the tranny fluid level...

4k and some change I did a complete fluid and filter change. There was some nasty fluid and the filter was awful. I cut it open to see how bad. It was very bad. It seems to me that the fluid is not being directed right to cause the problems I'm having. When it works right it is almost perfect then it goes to nothing like no fluid flow. And yes the fluid level is correct. Or to the dib stick. I guess it will be a take out to see the real problem.

I have good results!!
 

:) Well I finally had time to spend on this project. I drained the whole system and found very nasty fluid and filter. I guess the new fluid that I put in a few thousand miles ago broke the sludge loose and cloged the filter causing the tranny to starve for oil. I put a 1to20 ratio of trans-x to clean the system better. It now shifts and seems to have more power then it has ever had. I will drain all of that out also in about 150 or 200 miles. The thing that gets me is how small the intake is on the filter. It seems to me that a larger intake would allow for better flow. But I am no engineer. It also seems to have more pressure because I'm going to have to soften the shifts a little. The new modulator is prabably working now. Old cars need to have 2 or 3 fluid changes to be effective I guess. I'm very lucky it could have been real costly to fix. And a tranny shop could have ripped me if I took it there. I will post what the fluid looks like this time I change it. Alan

I had a very similar problem on my 91 300D. It wouldn't shift past 2nd and I couldn't get it into rev or park with the engine running. The problem was the governor hanging up. The governor can be removed without droping the pan. It is on the left rear of the transmission. Remove the rear mount, drop the trans as far as it will go, use some kind of strap or rope and pull the trans as far to the right as possible. Remove the large snap ring and remove the governor cover. Now this is where things may be different. On my 91 300d there was a snap ring behind the governor weights that had to be squeezed together and the governor assemble would slide out. On my 84 500SEL there is a lock nut and a screw that looks like an adjustment on the other side of the trans that releases the governor. Loosen the lock nut, and turn the screw about 1/2 turn left or right and that will release the governor. With the governor removed make sure the valve in the center moves freely. Clean the governor veeeery good, reinstall, and enjoy. At the same time, I serviced the trans using Moble 1 syn oil. The trans worked better than it had ever worked. By the way, this trans has 295,000+ miles on it.