W140 transmission when cold

[frog1520]

My W140 doesn't like the cold. When its left overnight, it acts strangely about 50% of the time...

It seems to have difficulty choosing which gear it wants when its in Drive! When I go from R to D (as I reverse out of the drive in the morning), it can take a few seconds to engage D. As you go along, it doesnt change up as it should - it seems to get stuck in 3rd and wont go any higher. Now, I know that when its cold it holds the gears longer to warm up the cat etc - i'm used to that but this is different! After a minute or so, it will decide its in the wrong gear and go into the right one with a jolt, and after that its fine.

Now, if you select gears manually for the first minute or so, the gears engage fine and its perfectly happy. i.e go from R - 1, 1 - 2, 2 - 3, 3 - 4, 4 - 5. After a minute or so, you can just leave it in D and then its happy.

I've had the ATF changed and the filter (in the torque converter as well) and they reported that the ATF was very clean and there were no metal bits at all in the old stuff.

I'm thinking it has to be electronic, because the gears engage fine manually. And after the first minute, its perfect - gears change smoothly and correctly up and down. Its got 110,000 so I guess the gearbox could be buggered, but I'm hoping its something simpler (and cheaper !

Any ideas?? Thanks!

 

[Birdman]

Mine used to do something like this as a result of my then vigorous driving style - the 'box 'remembered' I wanted to drive briskly and hung on to gears for too long for when I was driving more cautiously in the morning. Add in the tendency to hang on to 2nd or 3rd on a cold start to spare the catalyst and you have a maybe. Plus, if you're not in winter setting on the autobox.

Of course, it might be an electronic prob...

 

[Glenn Smith]

Mine went like this after i changed the oil, but is back to normal, took quite a while to sort itself out, i put it down to having the battery disconnected whilst i did the job. there is also a procedure for resseting the throttle pot electronicaly, no idea if it's valid but it did seem to help my gear changes, worth a try. can't remeber the exact procedure, i'll see if i can find it.

 

[panason1c]

Mine went like this after i changed the oil, but is back to normal, took quite a while to sort itself out, i put it down to having the battery disconnected whilst i did the job. there is also a procedure for resseting the throttle pot electronicaly, no idea if it's valid but it did seem to help my gear changes, worth a try. can't remeber the exact procedure, i'll see if i can find it.

Here is a c/p of the procedure....i tried it on mine and there was a big difference afterwards....if you still have problems it could be the MAF sensor playing games......


Resetting auto gearbox memory without disconnecting battery..

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Found this on the US MB slk forum... was a little scepticle at first until loads of guys reported that their cars were quicker off the line, changed gear at more optimum points etc, so I tried it and it does indeed seem to work!

The long way to reset the gearbox memory is to disconnect the battery for 30 minutes - but follow this quick procedure and it can be done in a couple of minutes!! Give it a try yourselves and post the results if it works!!

" 1. Get in your car, it doesn't matter if you close the door or not.

2. Turn the key to the on (not start) position, the position just before the starter turns over.

3. Press the gas pedal to the floor with the key in the "on" position.

4. Hold the pedal to the floor for five seconds, then turn the key back to the "off" position (don't remove the key), then release the gas pedal.

5. Wait 2 mins for a full alignment.

6. Drive the car as you always do.

Depending on your driving style, this may or may not be a big factor. I do a lot of city driving so I noticed a big change after erasing my history. It is not hard to do this, just follow the instructions - Key on, pedal down 5 secs, key off, pedal up, wait 2 mins. Keep the key in for the entire thing. Seems to work on mine. "

 

[frog1520]

Thanks for that - I've tried the reset procedure and it certainly makes a difference to driving (i.e feels quicker!), but doesnt solve this particular problem!!! Back to the drawing board....

 

[Sp!ke]

If its any use, I have a similar thing on my 23 year old w123.

Once warm its fine but when cold, its rather weird.

My point being it might be mechanical, possibly oil related.

 

[frog1520]

If its any use, I have a similar thing on my 23 year old w123.

Once warm its fine but when cold, its rather weird.

My point being it might be mechanical, possibly oil related.

Interesting!!! How long has yours lasted like that?!

 

[MBTECHNICIAN]

does sound like the oil level is low it would cause these problems

 

[panason1c]

frog1520...........A faulty MAF can cause similar symptoms.