Only reverse works (auto)

[mercakungen]

I am in a trouble.  I tried to do the very first test drive after completed restoration but only reverse gear of the automatic transmission works.
Oil level is normal.
The three position solenoid works as it should.
The constant speed solenoid works when foward and reverse gears  are selected. So there are some oil pressure on forward gears also.
I did remowe some screws and bits for zinc plating.  Maybe something went wrong during assembly process? Any thoughts?
I wonder if it is possible to make a mistake with that "stop screw " located front of the breather?

[ja17]

Double check the fluid level. Sometimes it takes a while to work the air out of the torque converter. Do you know how much ATF you used for the initial fill?

[mercakungen]

I checked the fluid level again. Engine running and shifter in P the fluid level is on upper mark. Same level shifter in N. Engine  stopped the level is 1cm above the upper mark. I used approx 4,5 liters of ATF. Reverse works well. Nothing happens shifter in 4, 3 and 2. I waited a couple minutes.

[mercakungen]

This problem is solved. One servo piston was not installed correctly.  The piston rod was not in its place. My mistake.

Now I have another problem. Gears forward start to slip when I touch throttle even just a little. Reverse does not slip.

The three position solenoid works as it should when the engine is off. How it should perform when the engine is running?

The Sun Valley Mercedes intructions on technical manual says that the left pressure switch should have 3 wires connected. Mine has only 2. The red/green  and that one which goes to the right pressure switch. I have removed all emission control wiring. Have I removed something important? There was a brown wire wich was connected from the pressure switch to one of the relay I removed with the emission control stuff.

[ja17]

As soon as you press the accelerator, the  transmission solenoid should move the linkage rearward, increasing modulator pressure so the transmission does not slip. When the engine is off or at idle, the linkage should rest in the center position with lower modulator pressure.

[Pawel66]

The Sun Valley Mercedes intructions on technical manual says that the left pressure switch should have 3 wires connected. Mine has only 2. The red/green  and that one which goes to the right pressure switch. I have removed all emission control wiring. Have I removed something important? There was a brown wire wich was connected from the pressure switch to one of the relay I removed with the emission control stuff.

I am not sure I see what you describe in the Tech Manual, Sun Valley material... The presure switches are 7 and 8 there. Anyway - be careful with that diagram as it is not 100% correct, I think.

Anyway: in the wiring scheme for Euro (and on my actual transmission) there is one wire coming out of each switch (red/green). They meet on the contact plate. This is the only wire needed to deliver ground to Constant Speed Solenoid - that is their sole purpose in this set up. You can, of course have the two wires from the two switches meet at the left switch, I do not think it matters.

The three position solenoid movements are driven by throttle switch (moved by gas pedal, as ja17 says) and the kick-down switch. In case of the wiring in my car and the diagram I have they provide + from fuse 3 to the three-position solenoid.

[mercakungen]

Pawel, I ment "Installation and adjustment instructions" in Tech Manual. My friend has a 250 SL which has exactly same wiring as mine. Wires to the terminal block have different size eyelets so I am pretty sure they are connected as they should.

Joe, the three position solenoid of my car does not work as you wrote.

Engine stopped: Key on the rod moves rearward. When I press the accelerator the rod moves to center position and stays there until the accelerator hits the kick down switch. That moves the rod forward.

Engine running: When I am starting the engine the rod moves rearward and stays there until I move the shifter from park. That moves the rod to center position. The rod stays in center position even I move the shifter back to park. I did not test kick down...
This is weird: I stopped the engine and turn  the key on again. The rod did not move rearward until I touch the accelerator. After  that the rod moves again as on engine stopped situation.
I am confused.

[mercakungen]

The "weird" problem is solved. Throttle linkage did not returned properly. I just moved the spring near to firewall to another hole.

I measured the modulator pressure which was just under 3 bar. I used port "5". Vacuum was disconnected and three position solenoid was in center position. The engine was idling. The pressure was close to 0 bar shifter on P and N.

The modulator adjusting screw has 3,5 revs to go until the spring retainer will be loose. If one rev means 2,1 PSI it is not possible to adjust the pressure to 4 bar by  this way. What should I do?

[mercakungen]

Edit: Test port "8"? (the one below the reverse band adjusting screw) vacuum connected:
P: 3 bar on idle . Approx 2000 rpm 6 bar
R: 0 bar  on idle / 0 bar
N: 3 bar / 6 bar
4: +5 bar  /  raising
3: +5 bar  /  raising
2: 0 / 0

I do not know if this information is any use. I just need to do something even I do not have a glue...

[Tom in seattle]

Mercakungen take a look at the thread "maybe a solenoid" started by me.  Several contributors have given clear explanation for the solenoid operation and these may help you solve your issue.

[mercakungen]

The problem is solved. A check valve was leaking. I had to remowe the transmission of the car to solve and fix the problem.

[Shvegel]

Good fix.  Luckily it isn’t a terrible transmission to remove.