Worn boost valve sleeve allows reverse oil leakage and worn end plug causes imbalance of pressure regulator valve
Ensure proper main regulator valve control with this boost valve and sleeve kit with O-ringed balance oil plug. Replaces 1991 - current OE boost valves.
Factory style sleeve, no O-rings
Common problems in vehicles with a 4L80-E transmission are uncontrollable line rise (upward of 500-600 psi), high line pressure in reverse, buzzing noise, broken direct clutch drums and/or broken cases. These problems are usually caused by reverse boost oil that enters the torque signal circuit due to a wear-created cross leak at the sleeve. High line pressure and buzz is created by oil leakage past the aluminum balance plug. The Sonnax replacement assembly 34200-03K eliminates these problems.
If you detect leakage between the sleeve and pump bore, use 34200-01K, which includes an O-ringed sleeve to compensate for pump bore wear and prevent pump scrappage. Kit includes instructions to retrofit parts dating back to 89.
Wet Air Tests can be done using either the reverse boost orifice or the torque signal orifice for this particular application.
Click here to view PDF if instructions do not appear below.
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