Welcome to the latest instalment of our DIY Mini Restoration series! In this guide, we revisit the Bogus 2 Mini build, focusing on setting up the transfer gears. This guide provides instructions and practical tips to help you achieve optimal performance for your Mini. If you need technical advice or assistance, don’t hesitate to contact the Mini Sport team. Let’s dive in!
Transfer Gears for Classic Mini
More Straight-Cut Transfer Gears: Noisy, Rattly, and Strong
Fitting the Straight-Cut Drop Gears
We start by fitting Mini Sport 1:1 straight-cut drop gears. These gears are designed to handle the extra power from the engine and reduce drag, ensuring less power loss during the transfer from the engine to the gearbox. In a Mini, these gears produce the characteristic chatter at idle and whine during acceleration. For any high-output engine, straight-cut drop gears are an essential part of the gear train specification.
Using a New End Casing
For this build, we are using a new end casing, identifiable by the sensor hole near the starter housing. Older casings can be refurbished with replaced bearings if necessary. This new casing also includes a crank breather hole. Always inspect the casing and bearings before fitment, just as you would with any build.
Checking Tolerances
Before bolting the gearbox to the short block, offer the end casing to the gearbox casing with the gasket in place to check the tolerance in the idler gear thrust washers. Roller bearing versions, often referred to as Timken bearings, are available from Mini Sport for enhanced performance.
Assembling the Transfer Gear Set
Here, you can see the inverted engine and gearbox with the full transfer gear set assembled, prior to attaching the end casing. Note that the bearing on the gearbox output shaft is a nylon casing type, which requires careful handling to avoid breakage. Some builders prefer to use the old-style roller bearings for the output shaft if they can find them.
Fitting the Primary Gear
After applying a dab of moly grease on the inner-bearing face, place the primary gear oil seal tool over the teeth. This inexpensive tool reduces the risk of damaging the critical oil seal. Ensure both the seal and the cleaned tool are oiled. Avoid touching the inside of the oil seal, as this can cause damage and lead to leaks from the clutch housing.
Installing the Primary Gear Guard
Don’t overlook the primary gear guard, as a leaking oil seal can cause significant damage. Make sure to place the C-washer correctly, pointing downwards with the engine at TDC. When checking the tolerance on the straight-cut primary gear, set it the same as a standard one. For race engines, allow a few more thousandths of an inch, particularly when using a cerametallic clutch, to prevent clutch loss due to tight tolerances when the clutch gets hot.
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Check out our gearbox components and accessories to find everything you need for your build. Stay tuned for more detailed guides in our DIY Mini Restoration series!
By using high-quality components, you'll ensure your Gearbox is perfectly set, leading to improved performance and reliability. Happy building!
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Don't miss out on the rest of the Bogus 2 Series!
This blog series is your go to for a guide to taking your Mini from a bare shell to a road-worthy classic. Check out the rest of the series for tips and advice from our Mini Experts for every stage of your Mini restoration!
This guide is meant to provide general guidance and a step-by-step approach to build your Mini's Gearbox. It is always recommended to contact a trusted professional if you are unsure about any part of the process or lack the necessary tools and experience.