AUTOBOX PROBLEM

[mobi]

I recently changed the oil and filter in my 1998 c200 petrol merc auto gearbox.
I did this because the mileage was 100,000 miles and it very occasionally stuck in first gear after it had gone from park to drive with quite a hefty bang jerking the car, this might happen just once in a few weeks of driving and you can run it up to the red line without it changing,have also tried moving the selector over to manual and changing down to no effect, it will then change gear as if nothing had happened.
After the oil change it seemed to have cured it but today, after about 300 miles since the oil change it played up again, pulled away from standstill and holding in first gear up to the redline for a few seconds then changing gear as normal for the rest of the journey ,has anybody got any ideas, could I try an additive in the box oil.?

 

[ELGRINGO]

gear box

Hi normaly very good gearbox , needs to go on starsounds likespeed sensor possibly playing up.

 

[television]

Do clean the contacts on the box ECU with a non drying switch cleaner (Maplins) There were loads of problems during these years with the CAN connections making poor contact, the end 2 pins.

Its worth a go

 

[Pathfinder]

Did you also drain the flywheel/torque converter?

 

[rapide]

auto box probs

as television electrical not mechanical there is tempreture sensor that holds on to lower gears to warm up the Cat perhaps thats gone up the wall! there are threads on here about 722.6 box that may help, the early box is a bit fragile if abused, later box tip shift late 1999/2000 on, very good.

 

[mobi]

Yes I did drain the torque converter, (it holds a hell of a lot of oil,don't it) but as it happens so infrequently I don't think it could be a temp sensor, but I could be wrong, I'll try cleaning the contacts next, thanks all.

 

[mobi]

Box ECU

Can anyone tell me where to find the auto box ecu as I want to clean the connections also the position of the speed sensor and auto box temp sensor, the auto-data book is useless as far as this is concerned.

 

[television]

I will try and find it, either on the bulk head in engine or under the dash

 

[mobi]

Have found the control unit for the autobox, it's in the front passenger footwell under the carpet ,bolted to the back of a metal plate, which is held in place with three 10mm plastic nuts .pulled out both connectors from their blocks and found some corrosion on the pins which I cleaned off.

Thinking back , about a year ago while driving around a right-hand bend in heavy rain I heard a sort of water sploshing sound followed by a squeal from my wife sitting in the front passenger as a large quantity of water poured over her feet,(not a pretty sight !)
It transpired that the scuttle area had a blocked drain hole and when I cornered right the water flowed left,poured over the lip round the air inlet for the heater, poured through the heater over the wifes feet and seriously soaked the carpet which I had to remove and found the underneath of the carpet is bonded to shaped foam rubber blocks to raise the carpet to allow flat plastic air trunking to feed air to the rear passengers feet. This was absolutely soaked through right into the foam rubber. it took weeks to dry out properly before refitting it to the car, so I guess that's where the corrosion started. It drives like a dream at the moment so I hope that's it.

 

[television]

Thanks for posting back on this,,,and I do hope its a permanent fix, it should be.

Big problem is with CAN signals they carry no current at all, so they cannot arc themselves better