The broken B2 piston problem is a well understood and easy to fix transmission problem with certain Mercedes 722.xxx automatic transmissions found in 126, 123 and 107 body cars. Although the car is drivable with a busted B2, it's a bit tricky.

There is a school of thought that says any pre 1994 MB with one of these should be replaced as preventative maintenance.

The good news is you can repair the transmission without taking it out of the car.