07-06-2018, 10:30 AM
I have dug various books on tribology out of libraries over the years. Some suggest that 20 is marginally thin for heavily loaded manual gearboxes ie towing caravans out of the Grand Canyon. Some sources suggest that the older mutigrades are seen by gears as the thinner. But with Seven powers, loadings must be much reduced cf moderns.
Abrasive wear is now largely countered by anti wear additives. The tendency to pit is probably increased with thin oil but few Sevens are going to do another 150,000 miles.
For synchro Sevens noise and leakage likely the main determining factors originally.
Abrasive wear is now largely countered by anti wear additives. The tendency to pit is probably increased with thin oil but few Sevens are going to do another 150,000 miles.
For synchro Sevens noise and leakage likely the main determining factors originally.