A Laboratory Study of Automatic Transmission Thrust Washer Wear

The wear and load capacity of automatic transmission thrust washers was investigated in a laboratory study in which flat, steel-backed washers with successive overlays of bronze and lead-tin alloy were rotated against alloyed cast iron surfaces. Test results demonstrated that the thrust washer antiwear quality of a Dexron automatic transmission fluid containing no sperm oil derivative was comparable to that of a sperm oil derivative-containing Dexron automatic transmission fluid, whereas thrust washer load capacity with the nonsperm oil automatic transmission fluid was somewhat higher than that with the sperm oil fluid. Wear was not appreciably affected by additive package concentration or type. Thrust washer load capacity was increased and wear decreased substantially by a reduction in the surface roughness of either the thrust washer or mating cast iron surface.