722.6 transmission - disabling/testing W setting
 

Hi all,

Is there any way I can test the S and W settings on my gearbox at all? I need to check if the switch is functioning correctly as there doesn't seem to be any difference between the S and W settings - I am aware the 'Winter' setting should start in 2nd.

Is there anywhere I can simply pull a fuse or relay to disable the gearbox switching into W mode at all?

Hi!
Just clean the switch mechanism, that can stuck in W setting - I had this problem before on both my E300TD.
You must feel the different if you start driving without touch the throttle pedal.

The W/S switch is part of the gear range recognition switch assembly. It slides a wiper across pads on a circuit board. If there is dirt in there it could definitely affect its operation.

The switch assembly comes out from the top of the shifter assembly
Put the car in Reverse, shut it off (you won't be able to remove the key), and set the parking brake
Remove the knob (1/4 turn on the black collar) and pull up
Remove the console wood
Remove the upper cover to the shift mechanism - clipped in place in several locations
Unplug the 2 connectors
The switch assembly is in a cartridge, the PRND4321 lights are the top of the switch assembly. Pull the assembly out and take it to a bench.
The head with the lights and the W/S switch is a top hat on the cartridge, it does pull off the remainder of the switch assembly.
Disassemble the switch housing - be careful, a spring will fly out - and clean the circuit board with alcohol.
Put the switch back together and make sure the W/S actuator is pushing the little lever which is in turn moving across the circuit board properly.

When you go to reinsert it there is a little witness hole in the side of the switch that has an R pointing at it. Rotate the selector until the white plastic piece shows up in the hole. With the gear selector in reverse this ensures the switch will be properly aligned when reinserted.

Thanks for the help guys, I will have a look into it this weekend, I am not 100% sure if its sticking/needs a clean but my guess is that if it doesn't really feel much different between the settings it might just need a clean.

Did you count the number of shifts? If you have access to a scan tool that will view trans computer data, you can see the W S switch and trans shifter position.

If no scan tool, you should be able to probe the trans computer inputs looking for the W S signal. I'm pretty sure the trans shifter position is either variable resistive or 4 bit binary.




At least on the 97 MY, the MB star must be removed ( it is on with 2 sided foam tape ) and a torx bolt removed.

I wonder if that was changed for 98, my knob is definitely twist the locking collar and pull up.

Sorry for the quick thread update, I haven't had a chance to count the shifts but it doesn't feel like the S and W modes really make much difference to me, it might be due to perhaps me needing to accelerate a fair bit owing to how slow the autobox is sometimes it might shift down to 1st even in W mode.

I removed the surround hoping that it was a separate button but it seems to be inside the shifter mechanism - I am tempted to remove the top cover of this to check inside with regards to the contacts, is it a simple case of pinging up the tabs?

If you sit at the lights in w with foot on the brake and select s you should feel the car go into 1st gear, there will be a very tiny lurch as it selects 1st.

Try a gearbox reset as well.

Thank you, will try that out, never thought of testing it like that, I have a feeling it might be stuck in W mode as it sometimes pulls away slowly but then sometimes feels like it's kicking down for more acceleration.

Here are details of how to proceed
Mercedes E-Class Reset and Synchronisation Procedures

Thanks for the help on this, I have tried a few things:

Sitting in drive, foot on the brake and switching between S and W - no change.
Manually set it to be in 1st only and checking acceleration vs in S and drive - manually setting it in 1st is much faster.

I will reset my transmission but I have a feeling it might be something to do with the actual switch on the shifter, its never really felt right so I have a feeling that either the contacts or the switch have gone. I believe the switch has basically set my transmission in W all the time meaning acceleration is slightly worse off the mark and it feels like a slight delay when moving off.

I can see that the shifter mechanism has a clip on top - plan to try and remove this to get to the switch inside and check/clean the contacts. I have already added some contact cleaner to the switch to see if that makes a difference but it might be a case that the switch has broken.

Are they difficult to replace or is it just a case of unbolting one and bolting in another? The car only has 237k miles on it so fairly new for a 90s diesel Merc.

It is easy to remove the whole shifter box.

4 X 5 mm hex heads and it just lifts off the floor. You will need to detach the clip in the linkage underneath.

Pro tip: I would get some string and tie that off that clip before attempting to remove it. It is not fun trying to locate that clip when it flies away.

Once you have it on the bench it is obvious how the top comes off and then you can extract the switch cartridge to clean or replace it.

Thanks guys, I will try and reset the autobox first and see what happens, I guess I also might not have noticed that much as when in W setting the box kicks down to 1st if going full throttle from a standstill. On the way back from work I did put it manually into 1st when at a standstill, makes quite a difference in the pull away! Its probably the first time I have ever pulled away in 1st without it starting to pull away in 2nd - really quite rapid and I can see why this car was the fastest diesel production car when it came out.

" Resetting " is only for the adaptives and fill volumes ( shift quality ) , it won't affect a 1st gear start.

For 96-99, from what I'm showing, the W / S switch status output at the trans computer is connector 1 pin 3 purple wire. ( Connector 1 has the most pins ) On the shifter it is pin 2 but the trans computer is easier to get to. The diagram does not say if the purple wire is pulled to ground or powered up to change states or what position = what condition.

If you are 2000 and up, the shifter communicated with the trans computer through CAN. If yours is 2000 up, the switch on the shifter or the input to the CAN translator isn't working properly.

Mines a 1997 so it will hopefully be something simple!