We have known for some time now that the standard MG gearbox in Bluebell was really not up to the job of coping with life in a race car. We have two gearboxes for the car, the idea being that one is in use while the other is being rebuilt, due to the fact that a ‘fresh’ box will only last 4-5 races before the baulk rings deteriorate and you lose the synchromesh to the point that gear changes become slow and ‘crunchy’. The long term solution was to replace the MG box with something more durable and with closer ratios to help keep the car on cam when racing. We have now installed a Tran-X SL72 5 speed, this gearbox is designed as a direct replacement for a Ford Type 9 as fitted to the Sierra. This has many benefits;
for a start the box is a ‘dog’ rather than synchromesh allowing faster changes, it has a close ratio gearset and is specifically designed for competition cars up to around 300bhp. The other advantage is that the type 9 is a popular swap for road going B’s so there is an excellent adaptor kit available from Hi-Gear Engineering (hi-gearengineering.co.uk) to make the install a simple bolt on conversion, we didn’t have to muck about fabricating an adaptor for the bell housing or make up a cross member or get a prop made, it all comes beautifully made in the kit. It uses the original clutch, release bearing and arm and even the slave cylinder is retained.
The only issues we had were due to the fact that we have a non standard crank and the supplied adaptor for the spigot bush needed to be modified and the Tran-X box is about 15mm taller than a standard Ford unit which meant that the transmission tunnel required some ‘adjustment’! Neither of these were anything to do with the adaptor kit itself.
The only downside is that, in order to bunch the other gears closer together first gear becomes much higher so getting off the line is going to need a different technique as the car is more inclined to bog down and lose revs, it’s a bit like trying to do a full bore pull away and finding the car is in second rather than first. There are some more pictures on the facebook page http://www.facebook.com/pages/Scruffy-Motorsport/170257223025246.
