my car is the 300ce-24 with a 5 speed auto(NOTE : no econ/sport mode on this model).The problem is that it shifts from 3rd -5th ,completely by-passing 4th.Benz service centre has diagnosed this to having a faulty transmission computer module.We replaced this and i only had it back for about two hours before it resorted back to missing the 4th gear.Then further diagnosis was done were they said i also need to replace the transmission solenoid valve, so we did that to, and after having it back working properly for about 3 weeks,it goes back to missing 4th gear again.I can always tell its gone by the amount of revs it should be doing at 60km or 80km's & also by shifting the lever from (D-5th gear, across to 4th above 80km's,)where their is no change in revs.The mechanics are now baffled as to what it could be thats causing this to happen,yet every time i have taken it back to be looked at after we replaced the computer module,& solenoid valve,they first would de-code the computer to refresh, and then all begins to work again,every time.But as i have mentioned before, this will last anywhere between 2hours and up to 3 or 4 weeks, before resorting back to by-passing 4th gear.Also ,once it goes,it never comes back until i take it back for decoding.The only solution they can come up with now, is that it's probably a loose connection somewhere in the wiring ,and that they will have to go about re-soldering every wire to do with it.A pretty daunting task,but at no further cost to me ,as i paid big bucks replacing those two things i mentioned ,which have made absolutely no difference to this problem.I have not asked for a refund , but for them do do whatever it takes to fix this once and for all.This problem has really dragged on,and it's getting me down.Does anyone have any knowledge about this,and what it could be? Are the mechanics at least about to embark on correcting this problem by the re-soldering of wires?Knowledgable reply's will be much appreciated. thankyou.

 

any theories ? PLEASE! cos the wiring that has to do with the transmission has also been renewed and still ,the problem persists.

 

anyone who has had this problem or knows something about it please go to mercedes tech talk forum and look up the above post thread . I need all the help i can get. It will be much appreciated. Thanks.

 

the latest is to my seemingly very unique problem is they replaced the wiring harness from the trans computer to the connector and a new valve body,and still the problem persists.Then i replaced the battery,as we found that under load it would go very low,which in theory may trigger my fault.This was some sort of breakthrough as we cleared the fault codes and all worked beautifully for 6 weeks in stead of just a few days,so maybe we are getting close to cracking this problem.Only problem now is that the transmission computer is not showing any fault now,their-for without a fault to clear,we are unable to get 4th gear back working.

 

I am a little confused. I thought Mercedes never made a 5-speed automatic transmission, until 1996.

 

yes,here in australia we had the 300ce-24 with the 5-speed auto as standard. It was optional in some other country's.This was the same engine ,transmission combo as the 300sl of the same era.

 

after relocating to a major city(perth)western australia,i took my car the biggest most established benz dealership (diesel motors),and they found the problem with-in two hours of my leaving it their.It was a stray earth wire,situated close to the battery area which was tucked under something,but not connected.these guys were very professional in their approach with lateral thinking,unlike the hillbilly's i had to deal with in a small regional town like cairns.i'm so happy now.

 

to avoid future problems I would get the fluid and filter changed as well. drain everything, even the torque converter and refill it all with amsoil.

 

I have a solution to my long running Auto transmission issue,well, sort of!
It can be found in the Tech Talk Section, headed "5 speed auto problem".

 

The six cylinder cars -- especially the heavy ones -- have had automatic 5-speeds since 1990 for the R129 300SL/SL320 and 1992 for the W140 300SE/S320.