automatic shifting

[piddler]

I don't think the automatic in my '67 is shifting properly. I live in the hills and when driving in town the transmission is constantly shifting. When pulling out sometimes it seems to up shift and then down shift again. When pulling uphill sometimes it will downshift and then up shift again.

I am not sure that it is going in 4th gear. The specs say that it should be turning 3145 rpm at 62 mph. It is turning about 3200 at 55 mph. I checked the rpm with the tach on my timing light. I am checking speed with GPS. (speedo does not work) The tach on the car read same as my timing light tach.

Is there a way to adjust the shifting pattern on these cars?

Thanks in advance for any advice and suggestions, Pete

[PeterW113]

Pete,

The transmission fluid level is critical for the box to work properly. If you have not done so already, I would start by checking that first.

Peter 

[Pawel66]

Pete,

I am not a mechanic, I just went through troubles with auto gearbox, have some observations and studied the topic on this forum. If your symptoms are connected to any specific malfunction and experts here will recognize it - they will chime in.

First of all - the car has to be in tune. Idle needs to be adjusted correctly, meaning all the parametrs like ignition timing, points, mixture need to be correct. It is all inteconnected with shifting gears in automatic as it is related to vacuum. Your brake booster needs to work correctly (no vacuum leaks).

I do not know if you know when the gearbox oil was changed in your car. Oil and filter change (if you have not done it) may be a good place to start. It will also give you opportunity to see and smell the oil you have.

How to check if the gearbox "management system" and how to adjust it you will find here:  https://www.sl113.org/wiki/Automatic/Start

The management system is three-way solenoid and the throttle switch that need to work together. Adjustments are about regulating oil pressure with a screw and a rod. The rod and the three-way solenoid can be seen through the opening in the center tunnel where the passenger's feet are. The second adjustment screw is for the reverse.

There are also numerous posts on the forum on this topic, e.g.

https://www.sl113.org/forums/index.php?topic=22622.msg161719#msg161719

https://www.sl113.org/forums/index.php?topic=24794.msg177342#msg177342

All these checks and adjustments are not very complicated. You need a pressure gauge and a banjo fitting. I made the tool for the adjustment of a piece of metal sheet. Just mind the pressure units.

https://www.sl113.org/forums/index.php?topic=22821.msg163115#msg163115

Why is your speedo not working? Is there an issue with the speedo drive at the gear box?

[piddler]

Thanks for the information and links. The transmission fluid was changed recently by a shop that works on these old Mercedes. I will check the fluid when the weather breaks and I can get the car out again.

I will also check into the links you provided.

Thanks, Pete

[Coops]

I think that the fact that your speedo is not working is not innocent!

The speedo drive is taken off the same shaft as the centrifugal governor. This governor provides the step pressure, which controls all the shift points for the gearbox.

So unless the cable is broken, in which case I apologise for a false clue.

It is possible to take the rear housing off to examine this assembly with the gearbox still in the car.

The process is described in the BBB CHAPTER 27-28

There are a couple of tricky points so if you decide to follow this path I will send some further information and photos