W124 - Gearshift problem, 5 speed autotr.

[zolu]

My current problem applies to a 1993, E280 with M104 engine and 722.5, 5speed auto box.
Auto box is misbehaving - Missing the 4. gear

1. Starts fine, up changes quite smoothly and at correct speeds.
2. At the 3 to 4 up-change point, it engages 4th for about half a second then changes to 5th.
3. Switching from D to 4th with the lever has no effect, it remains in 5th.
4. Down-changes are very slow and only happen when very low road speed is reached.
5. Manual selection of 3rd results in 3rd being selected after around 2 seconds (very slowly). If
left in 3rd, it behaves much as it should short of being reluctant to select 2nd except at very low road speeds.
6. Kick down (foot flat to the floor) results in 2 or 3 seconds of 'thought' and then off we go!

I am suspecious about the Transmission Controle Module (TCM) that have influence on the gearshift on 4. and 5. gear. It have a "Safe-Mode" where it skips the 4. gear and go directly from 3. to 5. gear (and 5. to 3.), when getting inproper signals from involved devices.

The diagnose tester also mentioned a mistake on the TCM. It is possible to reset the fault, but after some time (a day or two) the problem is back.

If it is the TCM making trouble, so the question is: Is it the TCM gone bad ?, or is it the devices given input to the TCM that is failing ? ... or are they all correct because a faulty part inside the tranny, is giving signal to the TCM that something is wrong, so the TCM is going correctly in "Safe-Mode" as it should ?

Thank You for spending Your time on helping us disabled W124 lovers !
Best regards from Luciano (Denmark

 

[ray_hennig]

Your time on helping us disabled W124 lovers !
Best regards from Luciano (Denmark

My 124 is disabled but, so far and touch wood, I am still functioning as well as can be expected!!!

Ho hum.

RayH

 

[zolu]

Well-well Ray, with all that cheap france white-wine I would be worried.

I got the problem back yesterday, so 2 days with a lovely 4.gear !

I heard from others who experienced the same problem that a common fault is code 9, the Control valve (Y3/1y2) going bad (getting disabled ...). But the diagnostic tool do not mention this fault, so .... still searching.

So now I have even more to think about ... could it be the cheap homemade tool given bad info ?

 

[ray_hennig]

Cheap wine - Yes, that's true ...

I did say, "... as well as can be expected." The wine does take its toll. But with prices starting at €1.70 a bottle, I can't complain.

On a more serious note, I am going to take the car to Mercedes in Périgueux where the top labour rate is €60 per hour. This is much lower than the UK and, I imagine, lower than in Denmark. Are the MB main dealers good at diagnosing older cars?

I'm happy that you've had a short period with 4th gear - I've forgotten what it's like.

Bon courage.

RayH