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Old 11-09-2017, 06:35 AM   #7
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Join Date: May 2010
Location: FP, NJ
Posts: 2,442
Default Re: 40 Ford Rear Axle Grease Seals

All of the seals in the rear end are "lip" seals. The cross section of the seals have a "V" shape. If pressure is applied to the "top" of the V, that pressure will push the sides out which will prevent any leakage in that direction. If pressure was applied to the "bottom" of the V, that would push in on the sides allowing grease or oil to leak past it. In all of the seals, hub, axle and driveshaft, the seals should be installed to keep grease or oil from flowing towards the brakes, thus allowing it to leak towards the transmission. So, hub grease is kept from leaking into the brakes and is allowed to leak towards the axle seal. The axle seal keeps differential oil from leaking into the hub bearing and allows hub grease to leak into the differential housing. The driveshaft seal keeps universal grease from leaking into the differential housing and allows differential oil to leak into the universal. The transmission should allow any pressure to leak to atmosphere. If a rear end is converted to open drive shaft, the differential housing must be vented to atmosphere at the top. All of this keeps the brakes dry!
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