what makes one 722.3 different from another?
 

What are the differences between 722.3s for different applications? Obvious to me are the bell housing bolt pattern and tail housing speedo drive. What other characteristics are or can be different?

1) Torque converter stall rpm. Any other TC differences within 722.3s? Multiplier ratios?

2) Vacuum modulator. What differs besides the color of the plastic case?

3) Valve body. Gear selection and shift timing based on selector position, modulator vacuum, control pressure input from engine throttle, centrifugal governor signal, kickdown switch signal, instantaneous gear setting. Oh, inane second gear start. Anything else?

4) Centrifugal governor. Is this what tells the transmission how high the engine can rev safely; i.e., when to downshift or else?

5) Secondary pump. Doesn't affect behavior.

Aside from interfaces and possibly beefier components, what is different between, say, a 722.370 (S500) and a 722.315 (123 300D)? Why can't Brian just swap a 722.321 (87 SDL) valve body into his 722.351 (300SEL) to have first gear start?

Thanks,
Sixto
87 300D

The statement by SST is that the springs in the valve body that setup the governor shift pressure points are all different for the diesel and swapping into the gasser will result in the vehicle shifting way too early.

Whether this can easily be corrected with a simple Bowden cable stretch is the question.

I'm still hopeful that the simple modification of removing the spring from the governor boost pressure valve will result in a FGS.

Eric still has plans to send the valve body from the 300SEL to SST to perform a test on that theory using the dyno as SST.

First a daft question - is SST a name of a company?

If you look in the ATSG manual (722.3 / 4) you can see that the vacuum modulators changed after 1981 - version A and B are shown. You are meant to upgrade to the latest version...

...on the same page (5) you can see that 722.310 transmission can have all of the colours available! .312 can have all but one colour (white) most transmission types listed by ATSG are either green or red - and many of them have been fitted with both green and red...

I get the impression from the ATSG manual that the colour of the vacuum dashpot is of little importance even though they have gone through to the trouble of listing virtually every type of transmission with virtually every colour produced. It is all very confusing.

Note also at the end of the ATSG manual the modulator brackets are different for the two types => page 107. Additional information concerning the modulators is conveniently hidden on page 119...


As for the governor I think this is the most important part of the transmission when it comes to shifting up or down. The governor is the mechanical / hydraulic brain that controls or manages the when to shift points in these transmissions - it is all calculated from road speed. (Thanks to Govert for sending me information about this - sorry it is in Dutch so it is of little use to most readers here)


The valve bodies are indeed complicated and the springs used within seem to have been changed quite a bit - see page 120 in the ATSG manual for example. Dieselkraut23 and whunter have been searching for part numbers - see

http://www.peachparts.com/shopforum/diesel-discussion/311685-k2-part-number-722-3-a.html#post2869018

http://www.peachparts.com/shopforum/tech-help/270894-k2-spring-kit-mb-part-numbers-needed.html

Differences highlighted in the ATSG manual include the TV plunger (whatever that is) see page 108; separator plate page 115; B1 piston page 116; and the lower valve body update information on page 120.


I have a gut feeling - and it is only a gut feeling that rather than changing the valve bodies more of a correct shifting effect would be gained by changing the governor. However, to be on the safe side matching both the governor and the valve body in the swap would probably be best.

EDIT:-

As far as I can tell from the ATSG manual, the gear ratios stayed constant between each type. I don't know for sure if that is the case - but I understand for top gear the output is usually 1:1 and only the final drive at the differential was changed for say a diesel powered vehicle and one with a big fat V8.

It's Silver Star Transmissions in Oklahoma.

I am still planning to send out my VB up to Silver Star. I need to have a rough idea of how long they intend to keep the thing also. If the VB from my 300SEL is the same as a 300E, I could just go grab one off a car in the JY and have no down time.

300SEL is back on the road after the valve job and running fantastic. Passed sniffer big time. :)

The different colours of vacuum modulators probably reflect the different ways in which vacuum is produced. Petrol engines have intake manifold vacuum, which is different from the low vacuum produced via the VCV of a W123 diesel. Diesels with a vacuum transducer have a different vacuum behaviour, which calls for a different modulator. That is my thinking.

The 722.3 transmission has green, red, black and white modulators. The German FSM lists the appropiate one for each type of transmission.

Valve spring change
 

Hey I've been playing with my 300SD shifting issues for over a year now. I bought a kit with new springs for the valve body to correct the hard 1-2 and very soft 2-3 & 3-4 shifts. Its the best $65 I have spent on this car. 1-2 is still firm but not neck snapping, 2-3 & 3-4 are perfect. A lot easier than replacing the 1-2 band. Search for Bulkparts.com and they sell it. Its not a simple job but if you take your time it worked great for me.

Just my 2 cents