Merl wrote - My T90 rebuild is finally done, and I must say that it went along much easier than I had expected. I used Rick's rebuild guide and a blowup picture for part name reference, never even looked at the shop manual for instructions on the rebuild. Overall, I'll give Rick's manual a hearty recommendation. Crown Automotive J8126806 Mainshaft Gear Nut for 46-75 Jeep CJ, SJ & J Series with T90, T14, T15 Transmission, 66-67 CJ-5/6 with T86 Transmission & 76-79 CJ with T150 Transmission - Self Locking Item: 52115.0078.14 But if transmission was really no good.. it was usually the transmission case.. which led to or resulted in other bad things.. Poor lube is probably biggest killer. I think this transmission is pretty sturdy, and I have taken apart several that worked fine…even though looking at the gears, you would think it was trash. Willys America Universal (CJs) & Military Service & Repair ... carburetor, electronic ignition, general service, electrical repair. 1946 CJ-2A Ron, California Engine rebuild, upholstery. 1952 M-38 Jack, California Multiple mechanical repairs. 1951 M-38 Richard, California Transmission, transfer case, major service, electrical repairs, brakes ...