I think the circular snap ring inset into the rear of the main gear is there for a reason...when the T84 is assembled, the roller bearings will not back out of the Main Gear. However, if you have had to remove/replace/remove/replace the main shaft in order to get the spacer sorted out, they will fall out of position if you are not careful. They can do that in two ways, first as you remove the main shaft one or two may fall into the main gear pocket and you may not even know it....until you try to assemble the T84! Secondly, if the snap ring is missing, as you draw back the main gear the grease adhesion to the roller bearings may pull one or two out which conveniently fall into the bottom of the case.
So...what is that snap ring for?
1) if in place, the rollers will not slide back with the nose of the main gear (yay!)
2) if in place, you may find it hard to get the roller bearings in there....unless the last one you slide in is where the gap in the snap ring is.
3) should you remove it? Uh, if you are using the same main gear then leave it alone and put in new roller bearings
4) if you bought a new main gear without the snap ring, trying to remove it from the old one and put it into the new one is a good idea
5) do you NEED it? Once correctly assembled you don't...during fitting of the main shaft spacer issues, it is a good thing to have.
6) I have never heard of anyone having the roller bearings walk out of the main gear...they only end out in the case or tipped over when you are removing/replacing the main shaft
GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
GPW 108552 4/17/43 Louisville, KY. USA 20371278 (DOD est./Tom W.)
Bantam T3 4582 10/29/42 USA 0173499 (est.)