DIMITRIAR

I have a w124 300ce-24 with the 5 speed auto (NOTE:their is no econ/ power switch on this model). My problem is that it shifts from 3rd to 5th ,their-by completely by-passing 4th.The benz dealer service mechanics diagnosed this as having a faulty computer module.We put a new one in .I had the car for about two hours with it working and then ,same problem comes back.I can tell this by the amount of revs it should be doing at a certain speed, and also by the manual shifting from D across to 4th above 80 km's, or vice versa, where their is no change in revs.So i take it back , and they then tell me it needs a new solnoid valve, so we replaced that to.I get it back where all is working for about 3 weeks and then ,same problem is back.They are now baffled,but what i can tell you also is that every time i have taken the car back for this problem, they de-code the computer and then it begins to work again.So i have had it back working correctly for varying amount of times,such as one week, then 4 weeks and now 3 weeks,and once it goes it never comes back without me taking it back for de-coding.They now think it might be some wiring problem,but don't know where to start.I have paid big bucks for the computer and solnoide valve for no result. I have not asked for my money back yet, just for them to do what ever it takes to fix this problem at no further cost to me. Is their any chance you know what my problem is ? I'm so frustrated. I look forward to your reply. thanks.

DIMITRIAR

anyone, have any theories. PLEASE!

m444

If you disconnect the battery for a few minutes, with the lights on (to help discharge everything). Then reconnect the battery, does it start shifting like you prefer for awhile?

DIMITRIAR

that i'm not sure,but i will try it and let you know.

DIMITRIAR

just tried the disconnect battery with lights on test,and their was no change to the problem.Does this result help your thoughts, through an elimination process?Another point about this problem i should mention, is that even when i select 4th gear instead of drive at say, the beginning of a journey,it still ignores my command,and by-passes 4th.(3rd-5th).So basically,once it goes,it never comes back ,till i take it back to benz service and we de-code and reset the computer.I am really appreciating your thoughts , and look forward to your reply. Thanks don.

DIMITRIAR

also, i should note that we also replaced ,with new, all the wiring from the computer module to the solenoid valve .Again,no change. thanks.

m444

So it is not 'learning' its self into this situation, seems to be a code fault condition?

There have been issues on some Mercedes, where someone spilled a drink into the console and caused the transmssions to shift funny. I heard this indirectly from a Master MB mechanic.

I am not sure where they place the transmission ECU on the Mercedes, but it sounds like under/near the shifter console.

Let's see, you have not replaced the gear selector switch, yet? Seems like a long shot, but it depends on how the car was designed. If a spilled drink can cause major shifting issues, I would bet on the gear selector switch.

Find a Master MB mechanic at a dealership, that really knows these cars, it may be Mercedes quirk.

You need to find someone, who has seen this before on your model car.

DIMITRIAR

thanks for your further insights, Don.I will keep the selector switch in mind. I spoke to the master tech at benz service yesterday,and through his talking with the main (benz technical assist department),the next course of action they will take is replacing some more wiring that is connected to the solenoid valve,apparantly they had only replaced the wiring from the ecu computer to a connector,now it will be from the connector to the solenoid.They also want to check the valve body,and some of the adjustment type valves with-in.By doing this next task,we must be getting closer to cracking this problem,as we would have replaced everything with-in the area where the diagnostic equiptment says lies the problem.I will keep you posted.

blackmercedes

The 722.5 is a tricky tranny. Have they ruled out a mechanical problem? Did they find any debris or other potential mechanical issues when pulling the pan?

teky

http://www.benzworld.org/publications/pub.asp?id=241
fault codes and how to get them

DIMITRIAR

Up until now, they believe the problem to be an electrical one.The next step should this re-occur is to check the valve body and check as you say for any debris with-in.So far,the oil has checked out ok,and today they are completing the job of replacing the rest of the wiring from a connector to the solenoid.Just to clarify what the diagnostic equiptment has said from the beginning,first it gave the number 8 -(replace tranmission control module),which we then replaced.Then and up till this present day it reads the number 7-(replace solenoid, and or wiring).We have replaced the solenoid, and are now about to complete changing the wiring.

DIMITRIAR

had the car back after they replaced the wiring harnesses from the auto , they also checked the fuse contacts to auto ,then stripped,cleaned and inspected the valve body ,checked terminals in connector x26, and over voltage protection relay.Checked and adjusted terminal retention to n15/1(ecu).Also ,no debris was found in the oil or around the valve body.So again, after this work and de-coding , and reseting the (transmission computer),i had the car back operating normally for about one day,and the fault has occured again.What now? even the benz technical department whom the mechanics have been working with under instruction seem to be baffled.Surely this can't be such an isolated,and unusual problem , on a transmission that is out their in big numbers, that a technically respected company such as benz cannot immediately pinpoint the problem.This is driving me nuts,and it looks like i need all the help i can get.I will not give up, because i love this car and i want that 4th gear.Your thoughts on solving this problem are always appreciated.

Fathead

Check out the news group, alt.auto.mercedes. Many highly skilled MB mechanics, collects, etc., subscribe.

I took the liberty of starting a thread, Australian W124 300ce-24 tranny mystery, that asks for members to help you. It includes a link to this discussion.

Check it out. The responses should offer some guidance.

Good luck.

Oh, but the way. Here's the note I posted on the other NG:


Subject: Australian W124 300ce-24 tranny mystery

Here's the link to a fascinating thread on MBWorld.org about transmission
trouble with a gentleman's w124 300ce-24 in . He seems at his wit's end.

I've suggested he monitor this thread. Figured with so many technically
advanced MB subscribers, certainly somebody on this NG can offer
suggestions, assuming his is a rare, but documented problem.

Thanks.

DIMITRIAR

so much appreciated fathead. i,ll be checking it out. Thanks again.

DIMITRIAR

just one thing ,fathead,could i get you to let me know the exact tital of the website i'm meant to punch in on the computer.Sorry for my ignorance,but i tried alt.auto.mercedes and came to nothing.

DIMITRIAR

no worries fathead, i found it,and put it on my favourates list.Thanks.

DIMITRIAR

now the tech department seem to think it has somthing to do with the valve body.Are we heading in the right direction? I have told them the problem seems to occur directly after the car has been sitting idle,like when i get into it in the morning after it's been sitting idle in the garage for the night.They say the valve body is heat related,so this may have something to do with it,but still they are not sure.I can't believe that the mercedes benz technical department of Australia is struggling to pinpoint and nail this problem once and for all.ANYMORE SUGGESTIONS OR COMMENTS, ANYONE PLEEEEEASE!

teky

only thing i can think would cause the problem would be the convertor looseing pressure over night a pin hole is enought to cause many problems, i really cant understand why their techs dont do a system pressure test with engine running on rolling road this would test the autobox out for sure they must have the gear to do at least that much or replace the g/box under warrenty

DIMITRIAR

many thanks for your thoughts and comments Teky.The latest news on this saga is that they are now going to replace the valve body for me , naturally at no charge to me.They believe this has to be it,but as has been the case,not 100% sure.The valve body is coming from Singapore,so it will take about two weeks to get here,but will still try to get one sooner.I just so hope this does the job. In the mean time,could you tell me what the converter is that you speak of,and where on or in the transmission it is located.Sorry for my ignorance,but i'm only just beginning to learn about transmissions due to what i have been going through.Is it also possible that (converter) also comes under another name.Look forward to your reply. Thanks.

teky

an automatic does not have a clutch peddle like the standard car so the clutch works through pressure which is generated by a torque convertor whis is in place of the standard clutch, i have pictures to help you understand how it works on my database http://uk.msnusers.com/autodatabase/gearbox.msnw
please feel free to join and copy any data you require you will also see in the mercedes section links to my specialits data on benzworld which show how to tune your car and check for faults and how to do it http://uk.msnusers.com/autodatabase/m.msnw

DIMITRIAR

thanks for the info teky.Yes i 'm not sure if they have done a pressure test,you would think they have ,being a authorised benz service center,but i will ask them when i take it in for the valve body replacement.Your theory on pressure loss regarding the convertor sounds logical,and i will put this to them . Thanks again.

DIMITRIAR

i am happy to say that the culprit was the valve body,which was replaced with a new one,and so far so good.One question though,ever since it was replaced i have detected something that was'nt their before.On a very light throttle, the change from 2 to 3,is not smooth,as their is slight hesitation,accompanied by a slight rise in revs.On more throttle, it,s totally smooth with no rise in revs.Also all other gears are totally smooth and normal,on a light or heavier throttle.Could someone please tell me what this is,and whether it's an adjustment issue,because the valve body is a new one,and as far as i know,nothing else was done to it.

DIMITRIAR

well, my original problem is back, so i,m looking for any theories and answers.This is really getting me down.

DIMITRIAR

the latest news with my on going unique problem is that after we found that my battery went very low under load,i installed a new one,and cleared the fault codes.What was amasing was that the 4th gear worked for 6 weeks before faulting.This broke all previous records by a mile.This can't have been a co-incidence,it may mean some sort of voltage problem to the trans.We checked the altinator,that was o.k.We cleaned the earthing to.At this point we are still exactly where we started in the very begining,no 4th gear.And what is worse,is that now the diagnostic led is showing no fault,their-for without a fault to clear we can not make 4th gear start working as we have in the past.

Fathead

Negotiate with the dealer for a remanufactured tranny?