The bearings can be lubricated by being submerged in gear oil, or by oil splashed about inside the casing.
Where the shafts extend from the casing, oil seals prevent oil leakage and the ingress of dirt and moisture.
Garter spring lip-type seals are normally used. They can be single or double-lipped, depending on the application.
They can also be hydro-dynamic type seals, with helical flutes molded into the sealing lip.
The flutes create a pumping action as the shaft rotates, so any oil at the sealing edge is drawn back inside the casing.
Since the flutes are moulded in one direction during manufacture, care must be taken to ensure they are correctly applied, considering the direction of shaft rotation.
O-ring type seals are mostly used for static locations such as the speedometer drive gear housing, while gaskets are used to seal the mating surfaces between the casing and retaining plates or housings.
In some cases, the gaskets may be used as selective thickness shims or spacers, in addition to their sealing function.
