I show an air check of a GM 6L80 pump and drum service pack which includes the 1-2-3-4, 3-5-R and 4-5-6 clutch packs as well as the Compensator Feed circuit. Air checking these parts on the bench will help you confirm subassembly build-out was done correctly or find and fix issues before the case goes together.

Also applies to 6L45, 6L50 and 6L90 transmissions.

I'll probably do a follow up video to this one showing the air check of the low reverse and 2-6 clutch.