I have an 87 W124, 300TD wagon, 200K miles. It has the 722.317 transmission. I am a mechanic, but have only rebuilt a few auto transmissions (BMW, GM, Allison), never one for a Benz.
It worked fine, some leakage at converter seal.
Safety switch malfunctioned the week before, have to hold shifter forward in Park, or drop into neutral to start it.
Went into town for breakfast, noticed a little surging
Backed it out of parking spot and put into Drive, no go in any gear. Fluid was 1/8 inches the low mark. I added a pint. It does not attempt to engage any gear with wheels up on hoist, not does it drop idle RPMs.
Trans working pressure 95-100 Psi, should be over 200. Same pressure in any gear, any RPM. I cannot measure Governor or Modulating pressure as it cant be driven.
fluid drained from pan and converter clean and smells right .
Pan removed, no metal flake, burnt cork, or any signs of trouble. Shifter rack moves normally, no obvious problems found.
Proceeding with removal of unit.
Is it possible the neutral switch could have anything to do with low pressure? This does not seem to be electronically controlled.
I am assuming the main pump has failed, but would appreciate any advice.

There are no electronics whatsoever.

I think a piston can fail and cause a no forward gears situation. I'm not sure which one (b2, maybe?) as I have not (yet) had to deal with this on my car.

x2. Most likely an internal failure like the B2 piston.

FWIW, the NSS problem is more likely misalignment because of disintegrated bushings in the rod between shift lever and transmission.

Sixto
98 E320s sedan and wagon

thanks. got it out, pulled pump, no issues I can see. I will pull it down further after work tomorrow, i've had enough fun for one day
There is leakage from the B2 piston cover

The failed B2 piston can cause exactly what you describe: no forward gears but reverse works fine. Easy to replace the B2 piston with the transmission out, also very possible to do with the transmission installed.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Remove the B2 piston cover and take it out. If it comes out in pieces, you've got your diagnosis.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

reverse is gone too. will see after work

I found a small amount of dark fluid in the B2 piston chamber, but no damage, scoring, or obviously bad seals in either piston on that side. The seepage was from the secondary pump cover plate o-ring, inspection finds nothing odd, other than a bit more clearance than I expected, although free of any signs of wear.
None of the troubleshooters I have found describe a loss of all gears including reverse, at least with no catastrophic damage.

I've ordered the full seal/gasket kit, neutral switch, rear mount, flex disks etc, will do the full teardown when the parts arrive

Before throwing time/parts/money at a potentially dead transmission, put it in gear and watch the output flange on the rear of the transmission. Does it rotate? If it doesn't, you have internal transmission problems. I'm surprised nobody has suggested checking flex discs or the output yoke of the transmission for stripped splines.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I checked that before calling AAA. Thanks