The Sunbeam S7 and S8 were made by BSA after they took Sunbeam over.
The dodgy worm drive was apparently caused by using the wrong oil, which ate the phosphor bronze parts - or so I read.
Frank
That echoes what I have heard about GL5 grade gear oil. I have been led to understand that many, though not all, formulations of it contain some sort of phosphorous-based anti-impact compound that doesn't play well with brass, copper or bronze bits. It is a commonly discussed topic on Triumph auto and Amphicar forums how GL5 can dissolve those brass gearbox synchronizers like salt on slugs, so all are urged to use straight GL4 instead of GL5 or those "GL2 through GL5" formulations. If GL5 is mentioned at all on the jug, then it is best to steer clear of it.
My 2005's Owners Manual specifies "EP 90 API GL-4" (450 ml) for its 5-speed box. I have never gone deeper into it than removing its outer cover, so cannot say if it has brass or other vulnerable metals within, but if GL4 is what is recommended, then GL-4 is what she gets. The issue there is that straight GL4 is rarely seen in the automotive lubricants section of stores nowadays. But you will find it in the marine section, since it's often used in outdrives. Having used up the last of my AMSOil GL4 jug, currently my bike is running Quicksilver (Mercury Marine) EP 80-90 GL4, and runs and shifts as sweetly as can be.
In view of the possible risks, if your gearbox calls for GL4 and instead has or even MAY have GL5 in it, maybe draining it and replacing with GL4 may not be the worst idea. Just strain and use the old stuff to lube your drive chain.
Topic: Not an Interceptor? (Read 5140 times)