Automatic gearboxes such as the 722.1 work by using hydraulic pressure to apply brakes or clutches to stop particular parts of a sun and planet gear system from turning. The 722.1 transmission has three sun and planet gear systems. (To read more general information about automatic gear boxes and sun and planet systems have a look at these links
http://en.wikipedia.org/wiki/Automatic_transmission and
http://en.wikipedia.org/wiki/Sun_and_planet_gear)
Here's a schematic of the 722.1 transmission
And here's a summary of the relationship between each element in the gear box and the desired gear.
I hope this will help with the many “is it my B2 piston” threads.
Here's a picture showing some names of the parts of the transmission.
You can find a nice exploded parts diagram of the 722.1 transmission here (
http://www.ganzeboom.net/images1/ganzeboom/parts/Mercedes/722.0,%20722.1,%20722.2.pdf).
I recommend you down load and print this pdf out before going any further!
At this stage I don't fully understand how a 722.1 transmission works. I can see how in principle it should,but there are certain parts such as the ident piston in the "tail cone" section that leave me thinking what the %^&^*& is that for?
If we get a long cold winter like we did last year I plan to work out exactly how the 722.1 (and perhaps also the 722.3) transmissions work. But that will be the subject of another thread.