For production purposes, the piston and piston pin snap ring design was changed for 2008 and later Tribeca 3.5L and 2010 and later Subaru Legacy and Outback 3.6L models.
The piston wrist pin snap ring was changed to a circlip style. As a result, the new piston features an access notch at each end of the pin bore.
The new style piston circlip and piston was incorporated into production starting with the following VINs:
Part name New Part # Old Part # Remarks
Piston set 12006AD651 12006AD650 A-size
Piston set 12006AD661 12006AD660 B-size
Piston set 12006AD671 12006AD670 0.25 OS
Piston set 12006AD681 12006AD680 0.50 OS
(New P/N piston sets include piston, pin and circlip. Old P/N piston sets include piston, pin and snap ring)
NOTE: New/old style pistons and clips cannot be interchanged. New style pistons must be used only with new style circlips. Old style pistons must use older style snap rings.