your ‘49’s rear axle housing has a built-in air vent in the case? I certainly didn’t
Some background: When I bought my 6107 25 years ago the differential pinion seal was leaking. The mechanic who replaced it looked everywhere on the axle housing and could not find a vent to the atmosphere. In addition to the motor, he said these were necessary on all housings that contained a rotating mechanism in gear oil, including the rear end and transmission, to prevent oil pressure building up which can cause leaks and the oil to foam (which reduces its ability to lubricate). To rectify this he drilled and threaded a hole above the right-side spring and screwed in a small venting valve he took from a junked car.
I had no further problems in this area until recently, when my rear axle housing started leaking gear oil on the right side at the junction of the axle housing and the passenger’s side brake backing plate. (There’s a special channel at that point to direct away from the brake shoes any gear oil leaking past the axle seal.) It was a small leak, but it became very annoying to see it whenever I climbed under the rear of car for any reason. I replaced the axle seal, and even installed a spare axle shaft on the assumption that might help, but the leak persisted.
Thinking the leak might be due to a crack or flaw in the axle housing, I bought a used one from ’49er Joe Cutler and started the formidable task of removing and replacing it. However, while cleaning up my new purchase I noticed a slit-like hole on the upper right of the back of the round part of the housing, which is the long-lost air vent. (See arrow in photo on next page.)
I then checked out the same hole on the housing still in my car to find that it was barely visible and completely clogged with dirt. I cleaned out the hole with a small knife which stopped the leak. Problem solved.
