Just for your info,
If you plan to replace worn parts (bearings, shift collar, etc) in your Sherman, John Smith and Red Rock Manufacturing (Phil Smith) will probably have what you need.
If'n you need to replace a badly worn Sherman counter-shaft, The Old Hokie can help on that too...
If you replace the Sherman countershaft and find the case is a little oversize, then use some loctite bearing retaining compound at the shaft to case mating surface upon istallation to seal that from a possible leak.
I did not seal mine, so I have a small seepage that makes its way out the cotter key hole below.