The Bull Pinion Seal is the primary cause of grease soaked brakes.
These tractors left the factory with leather bull pinion seals.
While structurally a robust looking seal, unfortunately the leather seal material deteriorates over time, the differential lubricant leaks out and soaks the brake linings.
New style Nitrile rubber seals have replaced the obsolete leather seals.
This is an image of Chicago Rawhide leather bull pinion seal that was original equipment on every "C" series tractor from 1948 to 1968.
Below is the modern Nitrile rubber seal that replaced the obsolete leather seal.
Bull Pinion Seal --
IHC #380922R91 is a
replacement part for the obsolete part 380921R91
Timken 450183
National 450183
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Other Possible Interchange
Part Numbers:
13690A
SKF
17494
SKF
IHC 75260H (Super C thru 240)
301334R91
IHC
378157R91
IHC
359790R91
IHC
378158R91
IHC
PH269
CASE
1189732
CHRYSLER