Here's another one of Ray's "Saddlebagrail" tricks to stop a four speed from leaking, two seals instead of one seal in the main drive gear where the mainshaft runs through the middle of it. The counterbore for the shelf is 1.250 inch in diameter and the inner diameter of the bushing that the mainshaft rides in is 1.000 inch in diameter. The counterbore is basically 7/32 or 0.21875 inch deep.
The seal is just under 0.200 inch thick.
Here's the new counterbore all the way to 7/16 or 0.4375. Again there are a lot of ways to do this depending on your skills and equipment. This was done, like my kickershaft counterbore, with a CNC mill via circular interpolation. The project would be well suited for a manual lathe as well.
Primer, retaining compound, and two seals. Use as directed.
Fancy seal driver. Once and...