4L60E Bonded Piston Kit, Hi-Per Blue 74960K

This is a Hi-Per Blue bonded piston kit for the GM 4L60E and 4L65E, part number 74960K (A74960EHPK). Bonded pistons have the sealing lip molded directly to the piston, so there is no separate lip seal to roll, cut or install backwards during assembly. It is a common upgrade on rebuilds and performance builds.

Fitment: 4L60E and 4L65E with the 16-bolt pan, 1997-up. Applications include 1999-2013 Silverado and Sierra 1500, 1997-2010 Tahoe, 2000-2011 Yukon, 1997-2014 Express and Savana, 1997-2005 Corvette, 1997-2002 Camaro and Firebird, 2003-2012 Colorado and Canyon, Trailblazer, Envoy, Hummer H2 and H3. Verify your pan style before ordering.

Why replace pistons: original rubber piston seals harden with heat and age and start bleeding apply pressure. That shows up as a slipping or flaring shift, a clutch pack that burns up repeatedly, or a unit that fails an air check at teardown. Fresh bonded pistons restore the seal on the clutch apply circuits.

On the bench: lube the bonded lips and the drum bores with assembly lube, install each piston with an even push (a lip protector or seal installer helps on the inner diameter), and air check each clutch circuit after assembly before the unit goes back in the case.