The OE bronze thrust washer behind the rear sun gear in GM Powerglide units gets compressed and distorted over time due to severe input shaft thrust loads. This in turn, creates a raised ring of bronze that blocks oil flow from the input shaft. Sonnax offers rear sun gear bearing kit 38208-01K, which incorporates an enclosed thrust bearing within a thrust washer. This kit eliminates compression and distortion due to input shaft thrust loads.
When using rear sun gears other than Sonnax current production, machining may be required to allow clearance for bearing.