CRD 2.7 722.6 transmission valve body

[OffroadSpike]

Hi.

I've been having some problems with the car, the symptoms I've been feeling are:

- Acceleration feels slugish on slow acceleration or feathering the pedal, if I go pedal to the floor it has plenty of power but doesn't feel quite right when cruising.

-I faintly hear some rattling noise/vibration from 1500rpm to 2500rpm, specially when going uphill and maintaining speed. I described this problem in other threads thinking it was a drivetrain/injector problem but I've discarded it comes from there

- Rarely, flares a bit when upshifting

I've removed the valve body for inspection/cleaning/renewal. The oil pan looked normal, some fine black and silvery dust but no metal pieces on it. I've put a new conductor plate in, the overlap valve and TCC damper Sonnax kits and a brand new Mercedes TCC solenoid.

Upon further solenoid inspection, all of them pass the ohm and "clicking" test, but 2 shifting solenoids were leaking air on the air pressure test (tested vacuum also with same results), I've ordered another 2 new Mercedes shift solenoids at around 80€ a piece.

https://www.youtube.com/shorts/2UnftYh9oG4

So, question time, what are the symptoms of leaking shift solenoids? Sure they can cause flares, but vibrations or rattling? Are the other 2 big black solenoids prone to problems? They are 250€ each and I'm not willing to spend that money just as preventive measure, I've not been able to pressure test them with compressed air since the opening they have is so big I can't fit a hose in it. Any other solenoid brand that can be trusted apart from geniune Mercedes ($$$)?

[JeanLuke]

For solenoids, see: https://www.rockauto.com/en/catalog/...+solenoid,8476

I'm not sure of the symptoms, but I do know a "moaning" when the TCC engages can be the TCC solenoid.

[Adrian D]

Can you duplicate the vibration when stationary? It might be a transmission mount that's going south...

Bad TCC solenoid causes oscillating revs once the converter is locked, at low load. My 2002 used to moan/groan when locking the TCC at low revs because of harmonics in the entire drivetrain. At some point I swapped in a 2004 TCU which locked at 70km/h and the noise was gone.

I believe both TCC and modulating pressure solenoid are PWM solenoids, maybe it's worth swapping them with eachother to confirm the modulating pressure solenoid is fine. I suspect that any oil pressure issue will cause poor performance.

Shift solenoids are only active during shifts.

3-4 flare is caused by wear in a certain clutch pack or wear in the 3-4 overlap sleeve bore. Can be improved with enlarging a certain hole in the valvebody steel plate. Can be masked by dialing in more torque reduction on the 3-4 shift. For my 2002 the Sonnax overlap sleeves did not help. When I installed a rebuilt valvebody I noticed the rebuilder used Sonnax overlap sleeves.

[OffroadSpike]

Originally Posted by JeanLuke

For solenoids, see: https://www.rockauto.com/en/catalog/...+solenoid,8476

I'm not sure of the symptoms, but I do know a "moaning" when the TCC engages can be the TCC solenoid.

When I accelerate hard I can hear some kind of whistle for a second

Originally Posted by Adrian D

Can you duplicate the vibration when stationary? It might be a transmission mount that's going south...

Bad TCC solenoid causes oscillating revs once the converter is locked, at low load. My 2002 used to moan/groan when locking the TCC at low revs because of harmonics in the entire drivetrain. At some point I swapped in a 2004 TCU which locked at 70km/h and the noise was gone.

I believe both TCC and modulating pressure solenoid are PWM solenoids, maybe it's worth swapping them with eachother to confirm the modulating pressure solenoid is fine. I suspect that any oil pressure issue will cause poor performance.

Shift solenoids are only active during shifts.

3-4 flare is caused by wear in a certain clutch pack or wear in the 3-4 overlap sleeve bore. Can be improved with enlarging a certain hole in the valvebody steel plate. Can be masked by dialing in more torque reduction on the 3-4 shift. For my 2002 the Sonnax overlap sleeves did not help. When I installed a rebuilt valvebody I noticed the rebuilder used Sonnax overlap sleeves.

The trans and engine mounts are new. There's multiple vibrations I feel, they are not strong vibrations but can get tiresome after driving for a while. One I can accurately point when it's happening is around 1000rpm, stationary or moving, the vibration feels/sounds like a rumble/droning noise, quickly disapears after 1200rpm.

Even if shift solenoids are only active during shifts, would they not properly sealing, as I showed in the video, leak pressure from the rest of the valve body and partialy try engage shifting all the time?

[Adrian D]

Originally Posted by OffroadSpike

When I accelerate hard I can hear some kind of whistle for a second



The trans and engine mounts are new. There's multiple vibrations I feel, they are not strong vibrations but can get tiresome after driving for a while. One I can accurately point when it's happening is around 1000rpm, stationary or moving, the vibration feels/sounds like a rumble/droning noise, quickly disapears after 1200rpm.

Even if shift solenoids are only active during shifts, would they not properly sealing, as I showed in the video, leak pressure from the rest of the valve body and partialy try engage shifting all the time?

The whistle during acceleration might be a broken exhaust manifold bolt or some noise that happens inside the turbo during spool-up, when the exhaust pressure is increased due to closing the vanes. I had it for a while now...

[OffroadSpike]

Hi.

I finally installed the rebuilt valve body but everything feels more or less the same. So I guess valve body was fine. I think the hard acceleration sound doesn't come from the exhaust or turbo, feels like coming from the transmission, anyway the contents of the pan were normal, just some clutch material and a few silvery dust but no metal pieces on it.

What I notice, and were wishing to fix with this, is my Desired TCC Slip and Actual TCC Slip values are very different on idle.



This was also happening before the valve body renewal. When engine cold, actual tcc slip is around 40rpm, but after driving for some time and warming up the engine, the actual tcc slip oscilated between 2 and 7 rpm. Is this normal?

What other tests can I do to know the transmission health? WJDiag is showing no errors.

[Adrian D]

At what speed are you checking this? Check it during driving, not standing still. And check before and after TCC lock-up.