When KAD decided to produce their own 5 speed race gearbox there were two main criteria which had to be met by the design. Firstly it should fit a standard gear casing without expensive modifications. Race engines can have blowups and replacing an expensive casing just adds to the misery. Secondly it should be direct drive in fifth, we figured that this would offer the maximum torque output at the point where aerodynamic drag was at its greatest: high speed. The other 5 speed boxes on offer were all of the over driven fifth type which meant torque would be lost when engaging fifth. The end result is a no compromise race gearbox that is easy to use with gear ratios ideally suited to today’s race tracks with their frequent slow to medium speed corners.
The compact gear train fits into a standard A+ rod change gear casing and has straight cut gears with face dogs, typical of conventional racing gearboxes. The gears are manufactured from a vacuum arc remelted steel (VAR), this is a very high specification material which has higher strength and greater purity than commercially produced steels giving stronger gears and allowing a narrower gear width and lower frictional losses. The selector forks are made from aluminium bronze which has good wearing properties and high bending resistance. The selector mechanism has been designed to offer a fast reliable change and the shift pattern has been arranged with first on a dog leg, to the left and back. This puts 2nd, 3rd, 4th and 5th in an H pattern, a great benefit when making high speed down changes from fifth to fourth. Quickshift gear levers are not required as the forwards-backwards change is faster than standard whilst the side to side movement is the same. This makes gear selection easy, precise and fast. Input and output shaft splines are the same as standard Mini allowing the same transfer and final drive gears to be used. The KAD pinion bearing support housing is used with the 5 speed to reinforce the free End of the mainshaft, this gives better pinion gear life as it prevents the pinion from trying to climb the crown wheel under hard acceleration (available separately for four speed boxes). A centre oil pick up pipe is also supplied as the laygear layout requires a different path for the pipe.
Gear ratios have been chosen with competition in mind,
and 1:1 in fifth.
Only available for ROD change gearbox.