The stock ribcase gearbox of any Sprite and Midget can be transformed into a superb racing box with the installation of straight cut gears! Not only does the straight cut design provide more strength and take significantly less power to drive but the ratios of the various gears are ideal for high performance racing! Yes, the nature of straight cut gears is that they are louder than the stock helical, but if you are racing you shouldn't care about noise, only performance. This gear set when installed will make a 948cc engine feel almost like a 1275, and a 1275 will feel like a 1500! You can always be on the proper power band of any motor!
The gearset can be fitted to any ribcase that originally used the 22G1100 laygear. The first gear and the reverse gear in the stock box is retained. The installation of these gears is often done at home but it is better left to the experts. GSK106 is the gasket set to use if you do it yourself!
Mini Mania can supply either just the gearset or can provide you with a ready to race gearbox!
Stock S/C Close ratio
2nd 1.916 1.722
3rd 1.357 1.255
4th 1.0 1.0
Dog engagement is typically limited to racing applications where fast, precise shifting is needed. Dog gear engagement works by having numerous large teeth or ‘dogs’ that mate into matching openings machined into the opposite surface of the drive gear. Unlike the synchro engagement, there is no synchronizing mechanism to assist in equalizing speed.
The "Ribcase" acronym for the gearbox as found as stock in most later '60's and '70's. The original design parameters were conceived around a small displacement low torque and horsepower engine and the "Smooth-case" transmission. The demands on this gearbox were well within design limits. Over the years the engines got bigger and bigger as did the weight of the cars they were installed in.
Elsewhere we've considered what alternative standard production ratios are available - but that still leaves you with the power-consuming and limited-ratio alternatives helical tooth type gears. Not desirable in a competition orientated car. The solution to this comes in the form of several types of straight-cut gear sets
These closer ratios, in conjunction with the very high rev limits of my Bonneville racing MG Midget put the power band right where it needed to be. Additionally, the straight cuts gave less parasitic power loss and less fore and aft strain on the transmission case. Watch the tach in this video, and keep in mind we're running 4:22 gears in the pumpkin. We took a push start to 30 mph, and I dumped the clutch at 9500 rpm. Note the rev drop on gear changes - considerably less than one would encounter with a stock ratio set. This run was for 126.684 in the flying mile. Once launched, the engine never left the power band, and the transmission held up beautifully . . . https://www.youtube.com/watch?v=aRYNKIMGCEs&feature=youtu.be If you install these yourself, get a piston ring compressor to hold the spring loaded ball bearings in place under the speed hubs, and be mindful of the pins holding the gear sets to the mainshaft - they're tricky. It's not an easy do-it-yourself project, but if you are patient, and work in a clean area, an average mechanic can do this with some difficulty, but to great success.