91 190E 2.3 transmission shift problems
 

ok, a customer's car... the complaint is overheating after medium drives... I check out cooling system, perfect no problems, no head gasket issues... so I take the car for a drive.
the thing rarely shifts out of 2nd, or third... at 40mph she's sitting around 5K

bowden cable is loose, fluid is fine. I'm not a transmission guru, but I know a car will overheat if driven all around town at near redline. she didn't know the transmission wasn't shifting right. (heck, the car moved forward, what could be wrong?)
anyway, I feel it's in the valve body, because as I was driving it around, I got it to BANG shift, and it upshifted ok, once.
I took out the downshift switch from under the accelerator, so that's not it.

anything I can test/check? I warned her that a trip to a transmission rebuilder is in order if I can't find something to test for...

You mean bowden cable is tight?

Check kickdown switch to make sure it's not stuck. Check vacuum line from intake manifold to transmission modulator for completeness (not disconnected, no leaks).

Check transmission modulator for leaks via vacuum line at intake manifold.

Reinstall bowden cable and adjust per FSM. Check throttle linkage to ensure it's in spec. ATF level and condition okay?

Is it a 722.3? If so ATSG says for "upshifts in upper speed range of gears only"

1) Bowden cable
2) Check regulator pressure - if the pressure is too low change the governor
3) Make control pressure regulating valve operable.

This is all on page 103 of the ATSG manual. Have you got a copy?


EDIT - warning - see ps2cho about the governor.

wow, it's a tiny car... not a lot of room to check things...
anyway, the bowden cable has slight slack at idle, I was going to adjust it loose, but it was...
"upshifts in upper speed range only"? that sucks... no economy shifting designed into that car eh?
I've removed the kickdown switch... no effect.
I do not have the astg manual... I'm a limited gearhead I guess...

If its got slack that's probably why....You need to tighten it. Tighter = shifts earlier, looser = later.

Not kickdown solenoid or switch otherwise it would be stuck in 1st gear and won't shift at all.

... tighter. ok, I would think that would make the transmission think the accelerator is pushed in... causing it to hold on to the gears, not upshift...

Exactly my thoughts.

Did you check for vacuum leaks at the modulator?

I talked to my transmission shop today, and they agreed, tighter would make the car hold the gears longer, preventing upshift, like I thought. they are NOT a MB shop, but they do work on them frequently.
they also mentioned the modulator, but I've not gotten under the car.
is the gasser vacuum modulator different from the diesel versions? I thought vacuum was just for firmness of shifts?

Adjustment of the shift cable controls what speed the trans will shift to the next gear.

Modulator controls how HARD the trans shifts.

If you disconnect the shift cable & drive, the trans should shift quickly into each of the gears.

MOST likely issue is a bad set of Teflon seals on the K2 clutch drum mount.

so... trans shop stuff, or diy stuff in my shop?:o