2006 Chevy 2500 6.6L Allison 1000

Complaint: Shortly after completing rebuild, transmission started slipping in 4th gear and setting code P0777 for Pressure Control Solenoid B stuck on.

Cause: Faulty Aftermarket C2 clutch piston

Correction: Replace piston with OEM piston

Part numbers related to the repair: NA

Year Make and Model of the Vehicle: 2006 Chevy 2500 6.6L

Mileage: 132,000

Shop Name: Falcon Transmission

Transmission: Allison 1000

Additional Notes: Vehicle came in for complete rebuild. The technician used aftermarket rebuilt kit complete with new clutch pistons. Vehicle returned after a few days slipping in 4th gear and setting code PO777. During disassembly the tech saw that the C2 clutches were burnt and during an air check on the clutch drum noticed it was leaking past the piston. He rebuilt the clutch pack with a OEM piston air checked it again and sealed perfectly. Always when installing a new molded piston check the drag on the piston, usually undersized piston will install with very little drag.

Pictures/Diagram: check photo below of piston

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