Leakage of Gear Oil onto Brakes

The most common reason for leakage of oil from differential gear cases onto brakes is overfilling of the housing. Under such conditions, the leakage will probably take place no matter how effective packing may be. Use of quite low viscosity gear lubricants, for example, SAE 75 grade in hot weather may also contribute to such leakage. Use of air pressure to help remove oil from the gear box may also cause leakage onto brakes. Failure of packing should also be investigated case there is a problem of gear lubricant on brakes.

Thickeners for gear oils

The use of thickeners in gear lubricants is not common:  hence, little space need be devoted to the subject. Where lubricating  greases  are  used  in gear sets,  soap  is  normally  the thickener  and  hence will  be  present. In  gear  housings  which  are not  tight, grease will  stay  in  place better  than  will  oil. Later  some  specific  applications  will be  mentioned  where  lubricating  greases are  employed, and  in  such  cases  the  type  of thickener   present will  be  evident.

Resins, both natural and synthetic, are occasionally recommended as thickeners in gear lubricants. Thus, resins separated from Pennsylvania residua are so used. Likewise, certain  grades of  polyethylene  are  thought  to  have not  only  thickening  power  but  also  to  contribute  film  strength  to  lubricants.

Inorganic solids, which  were  previously  mentioned as  being  used  in  gear oils  because of their EP  characteristics, have some  thickening  power  but  are  normally  used  in such  low  proportions that  bodying  is  not  evident. However, fine  silica  is a  component  of  some  semi fluid lubricating  greases  used  in   gear  cases  which  are not  tight and thus would  show  abnormal  leakage  with  fluids.