The output planetary assembly in GM 6L80 transmissions has a lube dam, or cover, that directs lube oil flow to the planetary lube feed passages. Over time, the lube dam allows gunk and sludge buildup, which chokes off lubrication. This commonly happens after overhaul, resulting in comebacks due to failed planetary assemblies.

In addition, the large OE pinion pins do not supply lube to the small gears, resulting in burnt gears, pins, bearings, needles and washers. Save the planetary assembly by installing Sonnax output planet saver kit 104584-80K, which includes upgraded pinion pins to supply continuous, critical lube to the small gears.