#46RES. 518, 46RE / RH, 727, performance rear band servo (GAS not 904). Many Chrysler A727, A518, A618, and A904 transmissions experience rear servo piston sticking / breakage, pin bore wear, and reverse band slippage. The servo piston has a tendency to get cocked in the bore and there is insufficient force to apply the band in a direct line. The high reverse line pressure continues to apply against a cocked piston, causing piston breakage. The bore of the piston also wears from side loading, resulting in insufficient band apply pressure.