Chevy Master Parts Book lists "Transmission main drive gear bearing retainer nut" as part # 591150, with the same part listed for all 3 speed transmissions from 1937-54. Description says 1 3/8" - 12 left hand thread. The illustration calls it "nut and slinger". The 4 speed uses a smaller nut.
Same part is used on GMC 3 speed transmissions of the same years.
Given the size, not exactly something you'd find on the shelf at your local Ace Hardware, but given the many years of use there ought to be an old tranny laying around you could liberate one from.
Last edited by Bill Hanlon; 12/14/2023 3:05 PM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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