Actually the B2 failure is one of the good things. The other tranny question running concurrently probably had this simple problem. To bad he already paid over 2100 to re-rebuild it.
The B2 servo piston was redesigned in later years and the replacement doesn't fail. It is easily replaced from the outside and is working in all forward gears except 4th. B2 is the Band for first gear, B1 is added for second, B1 is dropped and K1 (?) is added for 3rd and B2 is dropped and K2 (? not sure the nomemclature on K1&K2) added for fourth gear.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician