A revised first gear ratio was introduced on the TR-6 gearbox, changing the ratio from 3.14:1 to 2.99:1. This ratio change was effected by replacing the 33-toothed first gear on the mainshaft with a 32-toothed gear, and similarly, the 16-toothed first gear on the countershaft with a 17-toothed gear.
The gears concerned are directly interchangeable as matched pairs only. Details of part number changes are as follows:
|1st gear on mainshaft–33 teeth Countershaft gear, 1st & reverse16 teeth on second gear||152770)Fitted to gearbox number128107) CC89816 (3.14:1 ratio)|
|1st gear on mainshaft–32 teethCountershaft gear, 1st &reverse17 teeth on first gear||152803) Fitted from gearbox numberUKC 0662) CC89817 (2.99:1 ratio)|