1952 ES2 gearbox oil specification

You do need to steer clear of hypoid oils containing large amounts of sulphur (GL5 spec). The usual recommendation is for GL4.

However, a 50 grade engine oil is usually thought adequate. Not multigrade though.

Ian is correct, the thing to avoid is the EP additive (containing the sulphur compounds) which can corrode the yellow metal bushes in the box. We are looking for a compromise between an oil that is thick enough not to leak out too quickly from a box which is not that well sealed but not so thick that it fails to splash lubricate the bushes on the main (upper) shaft. 50 Engine or 90 Gear seems about right. Although Norton did recommend engine oil for the box Morris and others offer monograde gear oils without EP additives. I'm not sure about 30 or 40 grade in the primary chain case, the usual grade for that is 20 (also for the Roadholder forks).

Ian McD

Red Line gearbox oil for Harley Davidsons with "shockproof" is good stuff but expensive, comes in quart bottles for about £20. so catch it when you drain down.

Remember that the grading system for gear oils is different from that for engine oil (never understood why) - 90 grade gear oil has a similar (but not identical) viscosity to 40 grade engine oil at 100 degrees C.

Last time I asked for Castrol EP90 for my Commando, I was told it was harmful to the bushes, as previously mentioned, and was sold ST90 instead. Castrol's website doesn't appear to say anything to support ST90 over EP90 in this application, only that ST90 isn't suitable for hypoid applications, which suits us, no? Beyond that I have no idea ...

Red Line gearbox oil for Harley Davidsons with "shockproof" is good stuff but expensive, comes in quart bottles for about £20. so catch it when you drain down.