Technical Specification Change Points are too numerous to detail, however the following information on axle ratios will prove useful.
Axle ratio
4 axle ratios are available for the TR7 and 8 with the later '5 speed' axle.

3.9:1 This ratio was fitted to standard manual TR7 U.K., Eire, Thailand N.Z. and H.K.
and all other markets ( except US) up to VIN 402027 and manual SD1 2000
Suitability: - Road going 2ltr cars with no significant power increase.
Triumph CWP Part number: - TKC3282

3.45:1 This ratio was fitted to manual Rover 2.6, Rover 2.3 manual and TR7 US
1980, axle number CL1 onwards and all markets except U.K., Eire, Thailand
N.Z. and H.K. from VIN 402027 onwards.
Suitability: - Road going 2ltr sprint/Hillclimb/ race/rally cars with significant
power increase.
Triumph CWP Part number: - TKC2946

3.08:1 This ratio was fitted to Rover 3.5, Rover 2.6 auto, TR8 and TR7
Auto US VIN 402027 onwards.
Suitability: - Road going V8 conversions with moderate power sprint/Hillclimb/mild race/rally cars
Triumph CWP Part number: - TKC2945

2.84:1 This ratio was fitted to Rover SD1 Vitesse and Vanden Plas ESI
Suitability: - Hi Power V8 conversions with significant power sprint/Hillclimb/race/rally cars
Triumph CWP Part number: - TKC7375

General note:
All the above assumes standard 13" wheels and therefor standard rolling radius.
If larger 14 or 15" wheels are fitted then a higher ratio CWP should be used.
Further information is available on our website against each individual part number.