 | This article relies largely or entirely on a single source. (April 2019) |
| AP Automatic Transmission | |
|---|---|
| Overview | |
| Manufacturer | Automotive Products for British Motor Corporation |
| Production | 1965-2000 |
| Body and chassis | |
| Class | 4-speed transverse automatic transmission |
The AP automatic transmission is a 4-speed automatic transmission unit developed by Automotive Products and the British Motor Corporation specifically for use in the Mini.
It was unique in that not only was it one of the first transverse mounted automatic transmission units tailored for front wheel drive, it was one of the smallest in order to be used in the transmission-in-sump installation beneath the A-series engine used in the Mini, and later the 1100/1300 ranges. Another novel feature was that the transmission was designed to use the engine's lubricating oil, rather than conventional automatic transmission fluid (ATF). The units were manufactured in a BMC plant in Kings Norton, Birmingham which supplied complete powertrain packages (the unit required a unique engine variant) to the Longbridge and Cowley assembly plants.
Around the early 70s, the transmission received revisions with the new pre-oiler pump that prevented the 3-4 engine surge between shifts, and the quiet engagement into drive and reverse thanks to a revision valve that held the gears until it was fully engaged, eliminating a hard clunk heard on earlier versions of the transmission.
It was also later used on the Austin Allegro, and also in the original A-Series engined version of the Austin Metro, which remained in production until 1991 (outlasting the manual transmission version which ceased production the year before in favour of the heavily revised Rover Metro).
It also remained an option on the Japanese Domestic Market Mini until the demise of Rover Japan in 2000.