From what I know the 722.5 transmission is derivated from 722.3/4 transmissions by adding electronically controlled 5th gear. Is this correct?
Now is there such thing as completely hydraulically controlled 722.5 transmission, with other words with NO electronic controlled fifth gear? And if such animal exist, what is the part # and in which models it could be found, as well as what is the main visual/visible difference between both transmissions?

My understanding is that it's more electrically controlled than electronic. I say that because the box is basically hydraulic but they added an 'overdrive' that's controlled by a switching mechanism that's in turn controlled by a thing called the MAS box that also contains the fuel pump relay.

This MAS box does have some rudimentary intelligence but it's far from the true electronic control of the 722.6 box. That said, there are electronic issues. In my case, the 722.5 box refused to spend any time in 4th gear and it's overall responses became very sluggish. This was solved completely by clearing the stored fault codes that had somehow put the system into a sort of 'safe mode'. This followed the replacement of the engine and gearbox mounts but I cannot be sure of the exact cause of the problem.

So, the answer to your question is, "No, there is not a 722.5 box that's 100% hydraulic".

My question is, "Are you having a problem with a 722.5? If so, what?"

Regarding the models, mine is a W124 300CE-24 Sportline. The box was also fitted in the W129 SLs and, probably, in other 300-24s.

Any old way, there will be someone along fairly soon who will give a more detailed comment. Failing that, I recommend that you go to some of the UK boards because the 722.5 box, I think, was much more common in Europe. And if your German is up to it, try Deutschland.

Bon courage.

RayH

Hi,

I have a 1994 W124 E280T with the 722.5 gear box, with the same problem where the gear box skips the 4th gear and goes from 3 to 5, making the box very sluggish and partially ruining the driving experience ;(

My transmission had an overhaul 2 years ago and ever since it skips the 4th gear, and just really annoys me cause it seems a bit sleepy compared to the way it did before crashed and had its overhaul.

I went back several times and spoke to the mechanic who in the end agreed with me that it 'might' be that the transmission is skipping a gear, but that he also doesn't know what to do with it, since all the mechanical parts inside the transmission were replaced etc.

So my question is, how do I reset the fault codes in the MAS box.

Please help

Namy

The .5 5 speed is closer to the .3 4 speed with many internal parts interchangable. ( the .4 is a scaled down version of the .3 4 speed)

Does it try to hit 4th at all even for a second?

This might help

http://www.electrandiagnostics.com/shops/78/article11.pdf

It speaks of a no 5 th gear but offers insight on how the system works. It applies voltage to the 5 th gear solenoid in 1 through 4 gears then drops voltage to get 5 th.

IIRC with no outside input the 722.5 will shift 1-2-3-5. The electronic control unit makes the trans shift into 4th instead of 5th.

-J

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