Help-Trans fluid in the Shift Modulator vac. tube.
 

Need a little help on an trans problem on a 90 190 E 722.4 . I noticed ATF in the vacuum tube connected to the Shift Modulator. It's shuttering from 2nd to 3rd/ 25 to 36 mph. I have the replacement modulator and I know it must be set to 48psi for my trans. What I don't understand is how to pressure test the Modulator. My pressure/Vacuum tester only goes up to 10 psi and the Vacuum units are (in Hg) down to 30. What type of pressure gauge is used and where do you hook it up? How do you test the pressure to set the modulator and how do you set it when the pressure must be read at 31mph? If any one knows how to do this test procedure it would really help me out. My PM MB shop cd sends me to another section to perform testing, but that section isn't there.

Generally one disconnects the vacuum line to the modulator when setting the pressure. The pressure is read by connecting the appropriate guage to the modulator pressure port on the transmission, and running the car at 31 MPH while reading and adjusting the modulator. Thats it.

Proceedure:

1. Disconnect valuum line to engine & plug it.
2. Connect pressure guage to modulator tap on transmission.
3. Run car at 31 MPH.
4. Read pressure and adjutt the modulator till 48 PSI is achieved.
5. Put it all back together.

Thanks for the reply, do you know what type of pressure gauge is used? Fuel line testers are the only pressure gauges that I saw with scales that high. Won't 48 psi blow the hose off the modulator?

I dont think you understand. There is a port on the side of the transmission that is where you connect the test guage. You do not connect the pressure guage to the modulator valve in any way, shape or form. You need one that goes to 250psi since that is the highest pressure in the tranny. You disconnect the vacuum line to the modulator to set the modulator pressure. The modulator pressure is not present in the vacuum line that leads to the engine. The engine vacuum is what modulates an internal pressure used by the transmission. It is this pressure that needs to be set. And you do it without any vacuum present on the modulator. There is a mechanical setting on the modulator that you trun to set the pressure. The tranny has to be turning the wheels at 31 MPH while the setting is made. Watch the guage and turn the setting until the pressure is set.

Off the original topic, but that illustration is too good to pass up.

Crawling around under my 560SEL this morning, I noted some leaking from the rear of the transmission. If you look in the upper illustration, just to the right of the words "160-190 psi @ stall in drive". there is a bolt running fore and aft in the transmission, holding a black part to the transmission body. In the car, it has another piece plugged into it, with a wire that goes off someplace. Well, this guy is drooling transmission fluid. Please help me out, and identify it? I would like to buy a new seal or o ring or gasket, and stop this mess! Not a huge leak, but just enough to leave a mess there.

Also, is the transmission manual you used as a source for the illustration available someplace? I searched my CD Rom for the car, and found nothing on the transmission.

Thanks for the help!

The part you described is the kickdown solenoid, the wire is the kickdown lead and runs to the switch under the accelerator. The bolt holding the solenoid in place should be torqued to 14 ft/lbs (I think, working from memory here). There is a sealing washer between the solenoid and trans body.

Might try re-torquing it, especially if any tranny work had been done to it.

Manuals are available from ATSG. Automatic Transmission Service Group. They are on the web @ www.atsgmiami.com.

Mike, Dave thanks for the info.

No transmission work has been done, at least in the last 15K miles that I have owned it. I will put a wrench to the kickdown and see if that helps. I doubt it, less than 14 ft lbs, the bolt would be hanging out I think. Probably take a new seal to fix it right.

I am ordering the manual right after I finish here. $20 is cheap for any book, never mind for a tech manual! 722.3/4 manual is correct I believe.

Thanks!

Just got my new manual UPS to my door.

I am one happy guy! Great manual! Thanks Dave!

good find on the manual
 

Dave. I received mine UPS today for the 300D tranny. Based on what I have read so far the gov'ner is causing mine to shift the way it does. Great looking manual that seems to go into the kind of detail I need when I decide to work on it.
thanks