As some of you may know, I sprint and Hillclimb my ’75 Sprint which I have kind of race prepared for the discipline; even though it is road registered with an MoT and is taxed etc. it is not generally a road car.
To help with the faster venues like Goodwood and Blyton where gearchanges cost time, I have compiled a list of different gearboxes noting their ratios and predicted output speeds when applying the standard 3.45:1 final drive.
Clearly, these are hypothetical as they don’t take into consideration that car is shaped like a big unaerodynamic brick etc. but they are useful for giving a feel for the differences in ratios.
I’ve looked at the Ford type 9, 4 and 5 speed (V6 and straight 4) TR7 4 and 5 speed and RX7 boxes as the latter seem cheap and plentiful.
Looking at the figures, the best box by far for a better speed spread is the TR7 4 speed.
What can anyone tell me about these ‘boxes? Are they similar to an 1850 ‘box? It has been suggested that it might be out of a 1.8 Marina….hmmm…
Has anyone done the conversion…what might I need to do to make it fit…..will it be strong enough? I’m aiming for something like 150 BHP (at the wheels).
Looking forward to receiving your wisdom chaps!