Triumph TR6 A Type Overdrive - CP/CC 1969-1972
The ‘A’ Type overdrive unit that was fitted as an option to the TR6 PI cars operates in 2nd, 3rd and 4th gears. It provides a 22% reduction ratio to the engine speed for a given road speed when engaged. The reduction ratio is signified by the serial number prefix of the Laycock unit, In the case of the ‘A’ Type this is 22/, other cars used a different ratio unit, notably the Standard Vanguard at 28%, whose serial number begins 28/...... Overdrive gives 3 useful additional gear ratios, for use under all driving conditions. Creeping about in town the use of 2nd overdrive and 2nd gear saves on the continual 2nd to 3rd to 2nd gear changes. It nicely bridges that 2nd to 3rd speed ratio gap. The 4th gear overdrive provides effortless high speed long distance touring economy. The 3rd gear gives that little extra help for high speed overtaking when an upward gear change could best be ignored.