GM 4L80E Vacuum Testing - Pump Assembly

This video is an except from my '4L80E Basic Rebuild' series, updated with additional information on how to vacuum test a 4L80E pump cover (aka stator support) hydraulic circuitry via the Sonnax Vacuum test machine.

These transmissions are prone to wear in the hydraulic circuits which can lead to a number of problems including but not limited to:

1. Intermittent and/or chronic applied element slippage
2. Excessively harsh upshifts or downshifts that can lead to case or internal component damage or destruction
3. Torque converter clutch slippage, premature failure (P1870 or P0894)
4. Torque converter clutch drag, poor release characteristics (stalling at a stop)
5. Chronic overheating

I show each circuit being tested as well as display corresponding drivability symptoms and signs of impairment for each. I also show the installation of the Sonnax 4L80E-LB1 boost valve kit.

Performing testing like shown is an essential step in the rebuild process for these and numerous other transmissions. Identifying and either repairing or replacing the pump stator support will significantly drive down the risk of a come-back.