PeachParts Mercedes-Benz Forum - Overload Protection Device Switching Unit 1979 W116 300SD

Quote:

Originally Posted by Alec300SD (Post 3901134)

Yes, that wire with the boot goes to the kickdown solenoid.

If you pull back the rubber boot, there should be two wires on a ring terminal.
The screw may still be present in the ring terminal.

The green wire connects at its other end to the kickdown switch.
The green/white wire connects at its other end to pin 4 on the switching unit in the PS footwell.

If you reconnect the wire to the kickdown solenoid you should regain first gear starts,
and also regain downshifts when activating the kickdown switch under the accelerator pedal.
(So long as the other parts of the circuit work properly.)

Hi Alec,

My dad bought a few days ago a w116 300SD turbodiesel. But we have the following transmission problem: it won’t shift into first gear. Not in L or in D. If he drives in the 3rd or 4th gear, and he pushes the kickdown, it shifts down. But if he pushes the kickdown when he is in 2nd, it won’t shift down.
I read the following in this post

“First order of business, the abilty to successfuly have a mechanically induced first gear start should be tested.

Unplug the 8 pin connector to the switching unit and the 2 pin connector to the kickdown switch (located beneath the accelerator pedal).
Alternatively, unplug both the green and white/green wires from the Automatic Transmission Solenoid Valve.
Then, with the engine running, brake applied, select L and then select D.
When you then takeoff you should be able to acheive a smooth first gear start.”

We tried to unplug the 8 pin and e 2 pin connector, but it would not get into first gear.
We try to rule out that the transmission is not broken. If put it in L, should it always mechanically start in first gear? Or goes this electrically? Because if we put it in L, it just stays in second gear.
Any ideas? All help is appreciated.

My dad thinks the first gear is broken.