Hi: Have the same problem -did you find a solution??? BobThere are actually two things retaining the gear the key on the end (visible in the picture) as well as a roll pin passing through the collar of the gear ( barely visible end, at about 11:30 position. Looks like the key takes the load and the roll pin prevents the gear from walking off the end of the shaft.
There was plenty of oil, I will need to find some yellow metal compatible gear oil.