TECH: Main Drive Gear Seal Modification

Have you ever used the "fully enclosed - with metal Front and Backside" Main Drive Gear Seals?????  They press in really hard, and they're almost impossible to remove with sheet metal screws.  I think it's because the backside is enclosed, and they can't crush a bit.
I chucked it in the lathe and cut the back side out . . . now it should press in with a reasonable amount of press fit, and I can still get it back out with "a reasonable amount of effort."  It's like the old style stock seals now.  Remember: Always install your seal with the inner seal spring towards the oil, or on the same side as the oil you're trying to keep from coming out . . .

2 comments:

david ervin said...

Apparently, Harley installs the seals "backwards." Actually, you could debate which way they should point. The early Ironheads had a crank vent between the crank and the primary case that had a check to allow air to go into the crank from the primary case on the upstroke. Some call this an "oil transfer valve" but the valve was too high in the case to work that way. In any case, if that was the plan, it would have sucked primary oil into the crank for no apparent reason. My guess is that it was there to supply some clean air into the crank to facilitate the oil scavenging downstroke (if you throw some air away new air has to replace it).

So which way do you need to seal? Do you seal against the pressure downstroke or against the vacuum upstroke? Or, as you state, are you trying to keep the engine oil, that dribbles through the Timken, in the engine?

Noot said...

This particular seal is for the Main Drive Gear on a 4 speed transmission. But, I know what your saying about the sprocket shaft seal on a lower end. I weld that ironhead vent shut and vent the primary through a rear motor mount bolt I drill through the middle, connect a fitting and run a hose.