My SD isn't shifting right either. I only expect to fix it when I am willing and ready to go through the process of making sure that all control systems are set up correctly. Right now, I don't have a working pressure gauge so it ain't gonna happen.

Just guessing at various pressure and turning things doesn't work. Professor google turns up lots of how to's and service manuals for various iterations of the 722.xx trans. IF you have correct vacuum AND fluid pressures in the tranny, you can go through the process.

My understanding is that most flares & hard shifting are vacuum & pressure induced or at least can be adjusted away - but not all. One can't determine that hard parts are needed without knowing that the external systems are working.

My attempt at guessing instead of measuring was akin to urinating off the high side of a sailboat.

Here are a couple of links.

Mercedes-Benz Transmission, Steve Brotherton, ImportCar, February 2002

http://www.transtec.com/downloads/tech_inserts/mercedes/94642.pdf

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

The links make the assumption that the transmission is reasonably sound and that adjustments can bring it to a state of perfection. This is not always the situation.

If there is flaring, always start with taking away all vacuum to the modulator. If that eliminates the flare, you are on your way to tuning with the vacuum system. If the flare remains, you are stuck with increasing the modulator pressure. If the flare still remains, you've reached the end of the road, unfortunately. The control systems cannot fix a completely worn box.

You can't guess at what hte vacuum and modulator are doing unless you don't want to fix it. Professor Google has lots of information on the various 722 iterations.

Here are a couple of links.

http://www.transtec.com/downloads/tech_inserts/mercedes/94642.pdf

http://www.transtec.com/downloads/tech_inserts/mercedes/94642.pdf

Mercedes-Benz Transmission, Steve Brotherton, ImportCar, February 2002

Adjusting the trans without going through the testing process is akin to urinating off the high side of a sailboat.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

I tend to disagree with the above conclusion for the following reasons:

1) The performance of a worn transmission is never going to match any of the specs that exist for the box.

2) Many of them are near the end of their serviceable lives and adjusting them at the very limit of the range might buy some additional time before an overhaul.


While technically improper, moving the adjustment in the desired direction without testing can assist in the driveability of the vehicle.

AND measuring gives starting point and confirms that the expected changes actually occur.

Most of the literature says that a hard shifts point to high modulator pressure when vacuum is correct. It "seems" (to me) that VCV and modulator interact. I tried turning the modulator down without using a gauge. Perhaps I should have turned VCV up. Regardless, the modulator change didn't fix the shifting and I have no idea whether or not my turning the modulator T actually had an effect on modulator pressure.

Vacuum out of the pump has always been ~ 18' on my car with my gauge(s). It is less than that coming out of the orifice. I don't remember what the VCV pressure is but it does drop to 0.

Modulator pressure? I have no idea. It does (did the list time I measured) hold vacuum. The other vacuum systems except for the door locks are good. Door lock system is plugged with a bolt and is out of the shift system.

I'll go back and test pressures then measure what effect changes have. Now, I'm mostly flying blind. Will report back.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

You never stated the symptoms of your issue..........?

Although you believe you are "flying blind", I have a suspicion that you're flying in the wrong direction.

There are specific tests that you can make to put you on the correct path, even if accurate data points are not currently available.

Current symptoms are hard shifts from 1-2 & from 2-3. 3-4 is very acceptable. It is a little hard when moving from Park into Drive and sometimes Drive to Reverse. Shift points are ~ what is listed in various trans manuals.

I will go back and confirm current vacuum pressure and that the modulator still holds before changing anything.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Step 1:

Remove modulator line from T above VCV.


Step 2:

Connect Mityvac to modulator line.



Step 3:


Pump up Mityvac and see if it holds vacuum. If it does not, you found your problem at the modulator............either cap or modulator valve itself.



Step 4:


If Mityvac hold vacuum, route Mityvac into cabin and take vehicle for a drive with Mityvac pumped up to 18" or so. See if hard shifts disappear.


Step 5:

If hard shifts become very soft, some work is necessary to the vacuum system.


Step 6:

If hard shifts do not change with 18" vacuum, the modulator must be replaced.



See, I don't need any baseline data that verifies the various specifications for modulator pressure or vacuum to take you down a path of correction for your issue and I am definitely not urinating off the high side of a sailboat.