w126 1984 trans locked out of reverse - park
 

Hi
My 1984 300sd has developed the annoying habbit of locking me out of reverse and park on occasion. I pull into a parking spot and it will not go into reverse after taken out of park or not go into park from drive. I have been lucky so far being able to push it out and drive on. After driving on it will then get revrse and park back. Is it the nutral swtch or something inside the transmission giving the problem?? If anyone has had this problem I would appreciate advice before I get under it in the cold and rain.

Thanks
Robert

If you have not replaced the neutral switch, I would start there. Its not difficult to do. I am not a fan of trowing parts to see what happens, but in this case...

I have a switch that will go on as soon as it stops with the rain. I was hoping that it was not something inside the valve body because it wil not do it again for several mounths and will heal its self after driving. I have another transmission with a bad b2 piston so I can rob parts off of that one. I hope that they are the same from 83 to 84 300sd.
Thanks all
Robert

There is a valve in the valve body that is regualted by governor pressure to lock out the shifter going upwards from N - its a safety catch so the transmission does not grenade itself if the driver accidently shifts upwards of N while in speed above 8 mph.

In your case either the governor itself is jamming or the valve body has sludge deposits causing it to hang. The member called stretch or whunter can assist you in this.

Not what I wanted to here but it makes sense. Transmission will NOT move beyond N till it has been down the road and shifted (probably) one time. Other than that there are no complaints about the shifting - no flair and no delayed rough shifting. It will not give a problem for a long time after doing this.
I need warmer weather to go under it.
Thanks
Robert

I had that problem on my 300D. It was caused by the governor hanging up. I removed the governor, cleaned it and never had the problem again. The next time it does it, turn the engine off and see if it will then go into reverse and park. If it will, then it is the governor or a valve sticking in the valve body as Zulfiqar mentioned. The governor is easier to do than the VB so I would start there. Has the transmission been serviced lately? These transmissions need to be serviced every 30K miles.

Paul

the governor on that transmission has a metal gear drive and is sort of locked in by the secondary pump - unlike the 722.4 that the 2.5 turbo and the E300D has.

the workings are the same though.

And as mentioned - shut down the engine and try to move the shifter, if it moves - you need to get dirty under the car.