The KD valve on the parts trans is of a different type. Its shorter and fatter so won't work. I pulled the one out of the trans on the car. I am able to blow through it slightly and the o-ring on the end has a flat spot. So it's suspect. I cleaned and reassembled. There was an aluminum washer present that isn't present on the parts trans so not sure it should be there? I had 4 speeds for about a half mile then back to stuck in second at 40. Seems to be a pattern. Car warms up and then the trans starts faltering....quickly. So as I wait for my set of gauges to come in the mail what else could be going on? I'm tempted to spray out the original valve body with brake cleaner and re-install.
I'm tired and need a "win" at this point boys.

A friend suggested disconnecting the control rod from the bell-crank to see what it would do.
-First thing I noticed was that it will now start in 2nd. (Progress!)
-When it gets to the 2-3 change there is a flare, I back off the throttle and it changes to what I think is third but could be 4th. At 50mph it sounds like its in third though. This seems pretty consistent.
-The kick down switch doesn't seem to be doing anything In this configuration.
-Shifting is really soft and awkward but I need to adjust the modulator back inwards as I have it way out from the last experiment.

The gauges just arrived but in true Florida fashion we are getting nailed by an afternoon storm and I can't go outside and play anymore.

Finally got a chance to put the gauges on it today. Here are some numbers. I pulled my specs from the technical service manual and converted to U.S. units. I can't find the modulating pressure test port so didn't test it. I had to do this by myself so factor a margin for error between the speedo and the pressures.

Governing
Speed(mph) Spec(psi) Observed(psi)
(12.4) ( 8.5) (8 or 9)
(24.8) ( 22.75 (21)
(37.3) ( 34.13 (32)
(55.9) (49.78) (43)

Working (Stationary/Full throttle)

Shifter Spec(psi) Observed (psi)
L (193.43) (220)
D (123.74) (220)
R (256) (220)

D (N/A) 90@ idle

I would also mention I adjusted the control rod as long as it will go and shorted the rod between the bell crank and the throttle pedal. It seems more readily to get into 3rd at low throttle or when I let off the throttle real quick.

BP:

The working pressure is a function of modulator adjustment; backing out the modulator screw will reduce the working pressure.
The modulating pressure port is just forward of the modulator; it is at the very back edge of the main case. Adjust for ~ 70psi in D, stationary, full throttle.

Should I be looking for working pressure to come down and be more inline with spec? If all the pressures are close then does this look like a valve body issue?
Thanks.

Modulating pressure was reading about 60 so I turned the adjustment clockwise inwards to get to 70psi. Now the working pressure is 260psi in drive full throttle stationary. Could I have the wrong fluid in this thing? Castrol transmax import multi vehicle. It says Dexron 3 and prior?

What are the thoughrs on replacing the valve body with s brand new one? High working pressure/ normal modulating and governed pressures makes me think it’s a blockage issue. Could a valve body even solve this?It’s not cheap but there is one on eBay right now.

A friend recommended a pinched cooler hose or blocked cooler. That would make sense as far as high working pressure is concerned. I’ll check it out this weekend and report back my findings.

I thought I had posted after you did the pressure test, must not have made it.

You need to get a hold of a hydraulic diagram that shows activity ( the colored ones that show each range )

For most trans, the cooling / lube circuit is fed and regulated from the main circuit and a blocked cooler won't / should not cause the shifting issue. There is a bypass valve that allows for a blocked cooler so the trans won't be starved for lube.

I’ve got a transmission FSM in the mail heading my way so hopefully it has such a diagram. It just doesn’t make any sense why the working pressure would be so high. But that high pressure could explain the 1st gear starts and reluctance to upshift I would think. I need To chase the source of overpressurization and not the lack of shifting at this point. There is a cascade effect going on.

Working pressure is controlled by the cable from trans to throttle .( or on other trans, the vacuum modulator ) This is called throttle pressure for most trans.

Have a look at a valve body diagram, specifically the 2 - 3 shift valve. Many times there are springs to fine tune when a shift occurs. If a spring in the valve is broken, it will affect one shift point and not the others.

We need to confirm if this trans is designed to start in 1st or 2nd. If designed to start in 2nd and it regularly starts in 1st, throttle pressure is too high.

We haven't even gotten into cross leaks, this is a real difficult problem to find. ( This is where the valve body halves warp and cause leaks between circuits. )

BP:

1) Connect the dots.
2) Back off the modulator.

Forgive me guys if these seem like stupid questions but this is my first go at a Mercedes diesel and an auto tranny in general.

Frank: If I back off the modulator then I potentially solve the over pressure issue but then the modulated pressure is going to be too low. Right? I did drive it with the adjustment adjusted way out (CCW). and didn't see an improvement although I didn't have gauges at the time and don't know what my working/modulating pressure was. I'm not questioning you but I'm trying to understand the logic if the spec is around 68psi and you told me adjust for around 70. It was at 60psi modulating and 240 working when I first hooked up the gauge. I adjusted to modulating spec. Again not questioning, and I appreciate the help but help walk me through through this.

97 SL320: The trans is a 722.108 and everything I've read indicates a 2nd gear start. It will start in second if I don't touch the throttle at all at this point or if I disconnect the control rod running from bellcrank to trans (This has the 2 rod setup, no vacuum or Bowden cable). See page 24 of the ATSG manual here for a diagram:

https://cardiagn.com/mercedes-722-1-722-2-transaxle-service-online/

Rods are currently adjusted for an early shift. (Accelerator to bell crank is adjusted short and bell crank to trans is adjusted long.)

The current valve body came out of a different trans with the stamping:
115 270 06 01027450 near the pan.
The source of this trans is a highly respected Mercedes tech friend of mine that knows what he is doing and said it was a working unit when pulled. He's far away/ busy and I'm just stubborn and want to figure this out for myself.

We did this because the original valve body in situ would not shift whatsoever except reverse and "A (1 or 2)" forward gear after a drain and fill with new filter. And it was recommended I try swapping them.

It is possible I have two bum valve bodies but I don't want to rule out anything else yet.

I'd also like to mention I took this to a local well respected transmission shop and waited a week to call on progress. When I called they told me to come pick it up because they were tired of pushing it around. Said they couldn't get it to start. Got it towed home by a friend of mine and the relay on the fire wall for the A/C clutch/ starting inhibitor was bad. Jumper-ed the wires and recharged my drained battery (they glowed the crap out of it) and it started right up. They were more concerned about my leaking oil cap making a mess.

So you see gents, I'm on my own. All I have is this forum. I'll gladly provide any information or perform any test. Just be patient when I ask stupid questions.

BP:

In the case of vacuum modulation (gas engine or diesel w/VCV), the modulator pressures do have some significance. With a fixed modulator pressure configuration however, the working pressure is the target pressure, as it influences both the governor pressure and the control pressure (throttle pressure), that are then balanced against each other to control shift timing. Now that you are able to measure working pressure, bring it down to close to the spec pressure, and note the effect on shift performance.

I adjusted the modulator until I was able to attain about 125 psi working pressure. I took it for a drive and it still seems to want to start in first with any throttle pedal. The shifts were extremely slow to occur. Almost like driving a CVT. The 2-3 shift is still inconsistent and is only brought on by revving really high in second then abruptly pulling the foot off the pedal to shock it into 3rd. I measured modulated pressure when I got back and it’s about 34psi. Half of what the TSM specifies.