Seals for gearboxes

Gearboxes need to be lubricated, no matter how many gears (gear pairs) are spinning in the case. Harley-Davidson has relied on oil for gearboxes from the very beginning, i.e. as early as 1915 - whereas in good old Europe, grease or semi-fluid grease was used for a long time. Grease will certainly stay in the gearbox housing longer, but it has disadvantages in terms of the smoothness and functionality of the gears. And oil is much easier to change when the filling is used up. That's why Harley riders have always filled the gearbox with oil.

Hints on changing gearbox seals

Mainly older Harleys before 1984 are the subject to regular seal changes. In Big Twin transmissions with five and six gears, the main shafts and the main drive gear are mounted in such a way that no excessive clearance can occur in the bearings during normal use. This is why the seal rings stay tight. In the older 4-speed gearboxes of the Knuckles, Pans and Shovels, these bearings are designed differently and are more susceptible to wear. The transmission shaft runs in a bronze bushing, the output gear in a needle bearing. Both bearings are susceptible to wear as they suffer from a lack of lubricant due to their design. Therefore, before replacing the sealing rings on the left-hand side of the gearbox, always check the play of the output gear in the housing and the play of the main shaft in this gear. No play should be felt by hand at either point. Any sensible play would make it impossible for the sealing rings to do their job.