Hello,
   The upper shaft is the powered shaft from the engine, the lower shaft is from the transmission to the hydriclic lift-all pump. The lift-all pump is a simple pump for raising plows, cultivators, loaders, or aftermarket three points. The lower shaft can be removed by removing the cotter pins and then sliding the metal cuffs toward the center of the shaft. If you don't plan on using the pump it is recomended by IH that the shaft remain removed. That being said, I have a #31 Power loader on my '52 H about a quarter to half the time and haven't bothered to remove the shaft when i'm not using the pump and haven't experanced any ill effects.
Hope this helps, and good luck
Aaron Dickinson
Mason, Michigan

1940 Farmall A
1946 JD B
1952 Farmall H
1952 Ferguson TEA-20
1953 JD 40 Crawler
1954 Ferguson TO-30
1956? Farmall 300

