Farmall M/SM

This is a technical question for all you Farmall folks that have
tried this but will a Farmall SM pilot bearing fit onto the shaft of
a Farmall M. I have a Farmall SM input shaft that fifth gear
slides onto for engagement and a Farmall M upper sliding
gear shaft and to mate these to together I know I need the SM
bearing to fit in the input shaft. It is my understanding that the
SM bearing was bigger in diameter but just wondering if the
inside diameter of the two is the same?
Thanks,
Trent
 
Late M and SM input shaft has the same opening size as previous M for the pilot bearing. Front shaft bearing on input shaft was bigger on a late M and SM and they used a different input shaft housing and a slightly different length front yoke. Several different pilot bearing numbers were used over the years with some difference in type but all should fit, at least the ones used after a snap ring was used to retain the pilot bearing on shaft after the spring of 44. More than one type pilot bearing retaining bolt used so need to make sure bolt and washer works okay for the main shaft. Have added the late input shaft and housing to 49 models up with no problems. If I remember right all those tractor input shafts use a outer pilot bearing race in input shaft with the thin retaining ring. Seem to remember some early tractors with a pilot bearing that outer race wasn't separate from rest of bearing. Not sure about memory though.
 
Thanks a lot thats a lot of great info to know, so they actually never changed the size of the ?sliding gear? shaft where the pilot bearing slides on? Just the size of the bearing?
 
I?m sorry I re-read what you wrote that the opening for both pilot bearings were the same size. I have just heard that they changed the shaft the sliding gears were on when they went to SM?s so I was just trying to figure out what was changed about the shaft and if the early M shaft would work with the late M and SM input housing
 
Think the last main shaft IH made as a replacement for M and SM was 355720R92. It was for and fit M and SM tractors. SM counter shaft had part of it between front and rear bearings bigger than a M. So all M countershaft gears won't work on a SM countershaft or vice versa. Top shaft splines and all the same size for both. Some main shafts had a snap ring to retain pilot bearing early on. Rest were with a bolt and some had a different depth bolt hole. So check for a bolt to short or to long if mixing parts.
 

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