Gearbox

The pre-SD1 4 speed Rover P6 3500 S manual gearbox has been used but the poor reliability of this unit, coupled with the fitting problems and the lack of a fifth overdrive gear ratio have made the unit a poor choice. So I swapped to the SD1 five speed gearbox as it is the ideal gearbox for the conversion and this is the unit that has been used in the Capri V8. The gear ratios are superior to the Ford  box and the fifth gear is an overdrive ratio. This gearbox seems to be the strongest unit for use with the V8. Some people do say to use the T5 from a Cosworth as these were also fitted to TVRs but if the SD1 box comes with the engine or you’ve driven the car then go with it. The box is narrower, higher and shorter and modifications are required to the gearbox cross member, prop shaft, clutch hydraulics, speedo cable and transmission tunnel. The standard Ford prop shaft is not suitable as it is the wrong length also the Rover one is unsuitable. Early boxes have a manual speedo cable and once the speedo cable has been charged this can be utilised obviously the speedometer will need re calibrating. The latter boxes are fitted with an electrical transducer this can easily be removed and the earlier type fitted. The tunnel will have to be cut and an extension fitted. The tunnel can be dressed up to accommodate the 5 speed unit although I have found it easier to cut the tunnel and make good in a similar manner to the original Capri one. Some minor dressing of the tunnel will be required to clear the edges of the larger bell housing. The gearstick fortunately is an approximately the right position and slight modification of the cut-out in the tunnel, towards the offside, will allow the gears to be selected. The remote on the top of the gearbox is a separate unit and this can be repositioned with shim washers if required. You do have to cut and shut it to achieve a nice throw-cut a piece about 21/2” out of the middle and weld it back together. Be careful when purchasing a second hand 5 speed gearbox separate from the engine, because this unit was used in a variety of different BL vehicles and apart from the different bell housing the clutch release arm pivot, release bearing carriers and gearstick remotes were different.

With such a powerful engine the Rover automatic gearbox is another suitable alternative but this requires similar modifications to the five speed unit. The gear selector mechanism has to mounted and obviously the auto has the added problems of an oil cooler and kick down cable.