The output planetary assembly in GM 6L80 and 6L90 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.
To clean out the lube passages, the lube dam must be removed — which requires destroying it. By cleaning the lube passages and installing Sonnax output planetary lube dam 104584LP, you can avoid output planetary-related lube failures and comebacks.