Check out the links at the bottom of the DIY they have loads of information and troubleshooting guides for the 722.3 and 722.4 transmissions
I should not be credited for all the information in this post it is just compiled from hours of searching and compiling information from many sources and putting it all together in one place to help assist those with this problem.
Recently I have seen many questions pertaining to the Modulator and shifting problems. I put together this DIY to help assist with the common problems and effects of a bad modulator valve or vacuum leak and how to change and adjust the modulator on the 190E.
Diesel Owners this is a good link referencing the vacuum system and transmission on the 190D. This references how to adujust the system to get the best out of the diesel vacuum system and transmission modulator. Mercedes-Benz Transmission, Steve Brotherton, ImportCar, February 2002
Below are common questions and this DIY will cover them.
My Transmission slips/flares on 2nd to 3rd upshift Most likely the K1 piston spring problem that is common in these trannys read here k1-spring-kit-install.html
My Trans Shifts to hard? Most likely a vacuum leak or modulator adjustment
White/grey smoke coming from exhaust after adding trans fluid?The only way tranny fluid can get from the tranny to the motor is threw the modulator vale vacumm line.
My Trans feels like it slips for a second and then catches after stopping at a stop sign? Or my transmission is slow to engage?Most commonly a low transmission fluid level. Caused by a leak in the tranny or bad modulator diaphram allowing fluid to get sucked to motor.
My trans has soft or slow shifts? Soft Shift can becaused by the modulator being turned to low or a broken or worn modulator pin.
Before you begin with replacement of a Modulator Valve you should always check for vacuum leaks. Vacuum leaks are the most common reason for modulator problems. Vacuum leaks are common on older vehicles due to age and cracking. Vacuum leaks can cause various problems such as tansmission shifting hard and power locks not working correctly on the 190E or a bad Vacuum pump or leaks on the 190D can make the modulator function incorrectly.
The valve going bad can cause different problems. One being hard shifts. The other common problem is the diaphram rupturing in the modulator, causing it to suck transmission fluid from the transmission in to the motor this can cause white/grey smoke from the exhaust and transmission fluid loss. If fluid loss has happened then you may get a slow reaction time when the vehicle is moved to drive or reverse from the park position or you may have it feel like it slips and then catches when you come to a stop sign and take off.
Knowing Your Vehicle Transmission Number and Where to Find it
To get parts for your Mercedes 190 series vehicle you will probably need your Transmission Numer. It can be found on the side of the transmission above the pan see picture (courtesy of Member Samoila Stefan)
or you can decode your VIN here to get your transmission number.Mercedes-Benz Club Russia | Mercedes-Benz / VIN
This is only good if you still have the original transmission.
Most commonly the first 10 digits of the number are the part number, the next 6 are the transmission number, and the last 6 are the serial number
(123 270 77 01 722 400
) Sometimes you may need this serial number because of changes made to that model of tranny.
Different Modulators For Different Models
Green 722.400,722.408 -722.403 722.410 Red 722.409,722.413,722.414
Recomended Transmission Pressure Per Transmission Model
722.400 .....................Green..................46 psi (3.2bar)
722.403 .....................Green..................44 psi (3.0bar)
722.408 .....................Green..................57 psi (3.9bar)
722.409 .....................Red.....................48 psi (3.3bar)
722.410......................Green................ ..51 psi (3.5bar)
722.413 .....................Red.....................47 psi (3.2bar)
722.414 .....................Brown..................41 psi (2.8bar)
722.416 .....................Black...................44 psi (3.0bar)
722.418 .....................Red.....................47 psi(3.2bar)To serial #813648
722.418 .....................Black ..................47 psi(3.2bar)From serial#813649
Removal, Replacement And Adjustment of Transmission Modulator Valve
You need to do this to properly check the internal hydraulic pressure of the transmission after installing a new modulator.
Overview of What to do:
You are going to connect a psi gauge to a test port on your transmission's underside near your vacuum modulator.
Then, turn the car on and make some adjustments, and then remove the gauge and you're done.
You need to set the pressure correctly. There's a right answer - it's not a rule of thumb or by feel measurement.
Each transmission is different and You need the factory presure for your transmission.
- 12mm socket and 1/4"Rachet
-you can purchase a transmission pressure gauge set it works better to me just thread it in.
You can get one hereTransmission Pressure Gauge ATD5550
for under $35
OR you can make one this way
1 banjo bolt scrounged off of an ALDA on a yard car. The ALDA is the square unit on top of the injection pump on a turbo model. There is a banjo fitting leading into the ALDA from some clear tubing. Thats the one you want. Take the hollow bolt, two washers and banjo fitting.
- a few feet of 3/16" ID vinyl tubing rated for 60 psi or more.
- a 0-100 psi gauge.
-teflon tape for NPT fitting
-ramps for front wheels. Jackstands can work too.
-chocks for rear wheels
-TDM (Tecnical Data Manual) pressure settings for your transmission.
-Make sure your homemade guage or the one you purchased is clean. Transmission fluid is going to go into this fitting, and then get sucked back into the transmission. You want this thing clean!
-attach your gauge to the hose fitting using some teflon tape.
- push the the ends of the vinyl hose onto the hose fittings on the gauge and the banjo bolt.
-make sure everything looks nice and tight. This stuff will be under 50-80 psi.
-wrap a plastic bag around the banjo bolt (keep it clean!) end of your gauge assembly and bring it to the car
Removal of Modulator
make sure you have the right fluid level in your transmission.
- put front wheels on ramps. Jackstands can also work, but get them up high!
-put e-brake on and chock the rear wheels. Safety first...
-turn car off and put in P.
-Remove the exhaust bracket form the rear of the transmission. You may also need to remove seporate the exhaust to get the transmission to lower enough to have good acces to the modulator
- Support transmission with a jack and Remove transmission crossmember by unbolting the two bolts on either side of the member and the transmission mount bolt. You may also need to unbolt the driveline carrier
Using a 1/4" allen socket with a long extension and a swivel ratchet remove the retaining bolts from the modulator.
-Remove replace modulator
If you are just adjusting the modulator you can leave the exhaust and transmount in tact but it will be very tight to work on.
It is also a good Idea to replace the modulator Pin which is located behind the modulator after removal these are know to break.
Setting the Modulator:
-make sure you have that pressure setting from the TDM handy
- a little below and to the rear of the modulator is a 12mm bolt. This is your test port. Unscrew the bolt and put it to the side somewhere...you guessed it..Clean!.
-screw in your banjo bolt or purchased guage. Point the hose up and to the rear of the car. BE VERY CAREFUL to seat the bolt correctly. Check again. If you dont, fluid will spew everywhere when you do the test.
-snug it down, but do not overtighten.
-look at picture this is how it looks, but you wont have red fluid in the line yet.
-check everything again, and crawl out from underneath the car.
-plug the vacuum line that dives down to the transmission from the engine compartment.
-start the car. Quickly look down and check for leaks.
-Fluid will be running down the tube, but wont make it to the gauge. A pressure reading will be registering on the gauge
-what you need to do next is make the adjustment. This is done on the modulator itself. There is a little black plastic cap that hides a t handle. To make the adjustment youll need to pull the cap off, pop the T handle out a little bit and screw IN(right) to RAISE pressure, and screw OUT(left) to LOWER pressure. Adjustment is a little bit at a time.
-the adjustment doesn't take long if you do it with the car running.
-once the correct reading is achieved, let the car idle for a bit and make sure the reading is nice and stable after the transmission is at operating temperature.
-turn the car off.
- take off the banjo bolt or purchased guage, reinstall the 12mm plug bolt. re install the modulator rubber cap. reconnect the vacuum line.
- remove chocks, take car off ramps. test drive
Be sure to view these links they will help you out alot with the 722.3 and 722.4 transmissions
ATSG repair manual automatic transmission 722.3, 722.4