Dumb Question..722.xx Transmision..Dumb Because..

[RonD]

Because I rebuilt the Transmission myself, but need help diagnosing a problem.
First off..I am not a professional mechanic and never have claimed to be.

I have rebuilt automatic transmissions for many years for race cars, but always American such as T-350's and Powerglides.

I have a 1988 E300 with the 722.xx 4 speed transmission. It has slipped bad since i got it (very cheap because of it) a couple years ago. I finally decided it was time to pull the trans and rebuild it.

I have several other vehicles so I was in no hurry to get it done and took my time (about 3 weeks of a little bit here and there). Upon disassembly, I found what I thought I would. All the clutch plates were pretty much gone!!. Replaced all the clutch’s and seals and yes, even drilled out the rivets from the K1 and K2 hubs to replace the piston seals. Replaced the modulator, filter and cleaned everything. Put it all back together and boom…seemed to work fine. No more slipping from 2-3rd. Adjusted the cable to get my shift points at about 2000 rpm, adjusted the modulator for a little firmer shifts and time for a road test.

Well, everything seemed just great until I realized I was not getting any 4th gear!!! I tried everything and still not 4th gear. The car accelerates well, shifts good from 2nd to 3rd when I start out in (D). Shifts good from 1st thru 3rd when I start in 2nd gear.

Okay, so now the dumb question. What in the world happened? Does it sound like a valve body related issue (I Hope), or more like the K2 hub? I certainly don’t what to go through dropping the transmission out of the car again unless I have too.
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Ron D.
1988-300E, 1998-E320, 1998-ML320

[C32AMG]

Did you change the sealing rings (rear hub) for the K2 drum? Does the transmission have the T seal for B2 PISTON? Did you also change the B2 piston case seal? Other possibilities (valve body) are K2 accumulator cracked, stuck K2 control valve.

[RonD]

Did you change the sealing rings (rear hub) for the K2 drum?

Yes, and it was quite tricky.

Does the transmission have the T seal for B2 PISTON?

It seemed more like an L but I guess it could be called a T seal.

Other possibilities (valve body) are K2 accumulator cracked, stuck K2 control valve.

I like this possibility most. The K2 control valve may be the culprit.
At the risk of sounding very stupid (because I do not have a shop manual for this transmission), which valve controls the K2 drum?

Thanks so much for your suggestions.

Thanks again,
Ron D.
1988-300E, 1998 E-320, 1998-ML320

[C32AMG]

3-4 plunger command valve, 3-4 command valve, K2 accumalor, K2 accumulator control valve and K2 shift valve. The Black seal in the B2 piston bore is very important, did you change that seal.

[RonD]

The Black seal in the B2 piston bore is very important, did you change that seal?

Yes, I did replace the seal. One thing I do remember when I was reassembling the trans was the B2 piston seemed to stay in when I compressed it to put the snap ring back on. I remeber thinking it would pop out once there was pressure behind it. Maybe it didn't?
I will have to pull the car back into the garage the begining of the week and check it.
If it stuck in, would that prevent the trany from shifting to 4th gear?

Thanks again for your time!

Ron D.
1988-300E, 1998-E320, 1998-ML320