The OE cast bronze thrust washer behind the rear sun gear in GM Powerglide units gets compressed and distorted over time due to severe loads. This in turn causes the bronze washer to seize to the input shaft or break apart into pieces, damaging the gear set. Sonnax offers rear sun gear thrust washer 38208-03, an upgrade that incorporates a steel core with bronze layers on both sides which are impregnated with a PTFE coating for decreased wear and increased durability.