Hey everyone! My husband and I recently became owners of a 37 Plymouth P3 Business Coupe. We're looking at replacing all the fluids and whatnot - you know - basic maintenance kinda stuff, but I'm trying to figure out what fluids to use for the transmission and rear differential. Any suggestions?
Fluids are for new stuff … your Plymouth uses 85/90W gear lube in the trans & rear axle, 20W or 30W engine oil, & 140W gear lube in the steering gear.
GL 1 spec for transmission gear lube. The synchro pieces are brass and bronze, The newer lubricants have additives that don't play well with those metals. Napa still has gl1 spec available. Unless you know for sure the engine has been recently rebuilt which included a thorough block boil out, most folks will recommend staying with a non detergent single viscosity motor oil. Detergents in modern oils will begin to loosen deposits, circulating contaminants instead of leaving them lay happily in the sludge layer in the bottom of the oil pan and other low spots.
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