Normally high temperature bearing grease is used for relatively low-speed shafts, especially front wheel bearings on cars (which get very hot due to the heat transferred from the brake). For the gear head I would use a standard general purpose automotive chassis grease, if I couldn't find out what the manufacturer recommends specifically. In Bruce's instruction manual, Shell Retinax EP2 is prescribed. That is a standard general purpose automotive chassis grease, but happens to have Extreme Pressure oil mixed with its soap base, rather than a straight mineral oil. EP oil is formulated containing an extreme pressure additive, usually sulphur, to act as an anti-seize agent in situations such as hypoid rear axle gears. The sulphur is extremely unhelpful to any machinery containing copper, bronze, brass etc., so I tend to avoid EP oils anywhere I can. However in this case a pair of spiral bevel gears is involved, and I doubt any copper is present, so the EP2 seems a good choice of grease.
If the gear head is grease-lubricated, at least one possible reason for using an open bearing with a separate oil seal becomes clear. If the owner installs a grease nipple into the lubrication plug hole and then applies a grease gun too vigorously, the oil seal will pop out without damaging anything inside the gear head. If a sealed bearing retained by a circlip was used, very high pressures would develop in the gear head and probably crack the housing.
Last edited by grumpy; 15/11/12 06:27 AM. Reason: Add detail
