The overdrive servo piston in Jatco/Nissan JR403E units is prone to cracking, allowing apply oil leakage that causes poor 3-4 shift quality and burned bands. The OE servo cover bolts stretch and break under normal use. As the cover becomes loose, it allows the piston to cock and break. Sonnax overdrive servo piston pit 62170-01K is thicker and stronger and will not break like the OE pistons do.
Replaces OE 88mm piston. Will also upgrade 75mm piston if used with new piston housing.