Gear Vendors Overdrive Units
Below are pictures of Gear Vendors overdrive Units for A-904 and A-727 transmissions. These units are based on the British Laycock-DeNormanville overdrive design that was used in many European made cars from the 1960s through the 1980s, including Volvos, MGs and Triumphs. It was also used in 1974 to 1976 AMC Hornets & Gremlins and 1976 AMC Pacers. The Gear Vendors version is a much stronger adaptation of the original design, with Gear Vendors stating that their units are rated for up to 1,200 horsepower.
The Gear Vendors units have extension housings that replace the stock Torqueflite tailshafts, and offer a .78:1 overdrive ratio. The units are controlled by a dash switch that allows both manual and automatic operation. With the switch in "auto" mode, the car will act just like it came from the factory with automatic overdrive. The overdrive will kick in automatically at 47MPH (or whatever the eprom is set for), and it will turn back off at slower speeds without the driver doing anything. With the .78:1 OD ratio, a car with 4.10:1 rear gears will act like it has 3.20:1 gears, and a car with 3.55 gears will act like it has 2.77 gears. The units can also be manually controlled to switch in and out of OD to provide six forward speeds - called "gear splitting". However, many users indicated that there is no real advantage in using OD in first gear, but gear splitting from 2nd to 2nd/OD and then to 3rd and 3rd/OD works very well.Photos:
- A-904 with Gear Vendors unit installed - Courtesy of SMR Transmissions
- A-727 with Gear Vendors unit installed - Courtesy of Gear Vendors, Inc.
- Big block A-727 with an older late 80s Gear Vendors unit installed. This probably came from a motor home. (Contributor unknown)