From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Schematic of a four-wheel-drive drivetrain with a central, front, and rear differential.
| Identifier | WestWitteringFiles\U\2January1930-September1930\ Scan079 | |
| Date | 15th April 1930 guessed | |
| DIFFERENTIAL REV 1ST | ||