The VCV controls vacuum to the modulator. It is there to soften shifts.

B's and K's in the shift chart refer to which brake band (B) or clutch pack (K) is engaged for a given gear.

The B2 piston is internal to the transmission and controls the brake band on the gear assembly. Transmissions wear out, when they do, things start misbehaving. A leaking seal or worn cylinder will cause fluid pressure leakage and affect operation. The more brakes or clutches are engaged, the more critical the pressure leakage becomes.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]