GEARBOX - Limited Slip Diffs; necessary parts for installation.

Fitting an LSD isn't as simple as replacing the diff cage unit. In all cases a certain degree of diff housing modifications is needed - material needing to be ground/filed away to provide clearance for larger diff housing cases and crown wheel bolts. Although it has to be said the Quaife diff is supposed to fit without these mods. I've never found that. The design and manufacture of the LSD to facilitate any other function other than that of a standard 'open' diff assembly precludes use of standard CWPs. So one suitable for an LSD is needed. Naturally Mini Spares/Mania supply these in an extensive range of FD ratios. The output shafts are also different. A much thicker spline type is used within the LSD assembly. Consequently a suitable pair of LSD-compatible output shafts are needed. Some folk still insist on running the archaic, power consuming Hardy-Spicer type driveshaft to diff joints - although this is the only real option for rallying unless a change in driveshaft assembly

Gearbox - Up-rating diffs and FDs

There’s a good selection of straight-cut final FDs available. Examine the FD table, and using information from

'Gearbox - Final dives, standard' and 'Gearbox - Formulae for car speed, etc.'

you can assess which would best suit your usage. Bear in mind that they’re noisy, make sure you select one that’ll fit your diff unit, and also consider that using drop gears will allow fine-tuning of the ratio where necessary. See

'Gearbox - Up-rating drop gears'

Gearbox - Up-rating diffs, FDs and ancillaries.

part numbers: C-BTA166, C-BTA167, DAM6624, BTA101, 2A7062, DAM5071, DAM6027, RPS1418, C-AJJ3385, C-22A1731, ...Read more

Gearbox - Limited Slip Diffs, What they're about

Modified engines producing more power generally induce owners to drive with greater verve, particularly when competing in one of the many motorsport disciplines. Terminology - LSD - Limited Slip Differential In fact this isn’t isolated to modified Minis. Owners of relatively standard machinery competing in a discipline or merely out on a country lane blast are subject to the same determination. The more verve/determination applied, the more of a struggle keeping your Mini on the designated track becomes. Generally the problem is down to grip - or more precisely the lack of it. Suspension modifications and extensive twiddling of geometry settings can provide improvements in stability, both for straight lines and turn in/mid corner performance. But even throwing bucket loads of cash at super high grade dampers, and the odd arm/leg/lung handed over to ‘professional’ chassis tuners doesn’t solve the particular grip problem we’re interested in here - corner exit/acceleration grip, or

GEARBOX - Limited Slip Diffs, what's available.

‘Salisbury’ is the word banded about by most un-enlightened folk when discussing LSDs for Minis, mistakenly believing the word covers all Mini orientated LSDs. This is grossly incorrect. Terminology - LSD - Limited Slip Differential The ‘Salisbury’ was designed in the ‘50s at a time when racecars were a good deal less sophisticated than today. Tyres were usually cross-ply with severely limited grip due to poor compounds developed ostensibly for rear-wheel-drive cars; the front wheel drive of the Mini being a rarity. And tracks were more than a little ‘bumpy’. Agriculturally built cars needed an LSD designed along similar lines; enter the Salisbury - effectively developed from a tractor diff. High static pre-loads were more than common to help compensate for severe short-falls in chassis, suspension, and tyre design. To all intents and purposes the diff was practically locked up, making the car a real beast to drive.

C-AJJ3385 – Twin Cross-pin diff assembly.

This differential unit incorporates a twin cross-pin assembly and four planet gears. The kit is made to accept standard production crown wheels and standard differential output shafts of your choice

C-BTA166 COMPETITION DIFF PIN

Every effort has been made in the production of this pin to ensure its maximum specification with regard to material, heat treatment, and finish ground size.

The planet wheels to be used should be checked on the pin prior to assembly to ensure a reasonable tolerance. If excessive play is evident, select different planet wheels.

Due to excessive manufacturing tolerances, it should not be assumed that new planet wheels will be okay. Selection by trial and fit should be employed. If intended for arduous use Minispares recommend using the Molybdenum coated pin C-BTA164.

Use of high detergent content engine oil will drastically...

25 years ago - The X Pin Diff was developed

The X-pin concept grew out of development work carried out by David Hirons in the mid Eighties to resolve the problem of persistent diff bevel gear and carrier failure on rear wheel drive Ford Escorts and Lotus Cortinas. The torque capacity of the diff could be increased by adding two extra bevel gears.

25 years ago - The X Pin Diff was developed

The X-pin concept grew out of development work carried out by David Hirons in the mid Eighties to resolve the problem of persistent diff bevel gear and carrier failure on rear wheel drive Ford Escorts and Lotus Cortinas. The torque capacity of the diff could be increased by adding two extra bevel gears.

GEARBOX - Final Drives, standard

FDs are ultimately responsible for the way your Mini goes after engine, gearbox, and under carriage tweaking has been applied. part numbers: DAM3647, 22G443, 22G101, 22G340, 22G338, DAM4131, 22A399, DAM4162, 22G940, 22A399, DAM2677, DAM2679, 22A411, 22A413, DAM2808, DAM6327, DAM2808, TCC10001, Terminology - FD - Final Drive/diff ratio The aforementioned and the degree to which it has been done will affect the decision as to what FD is required. They’re also responsible for much discussion between many tuning freaks, and confusion to the less informed. There’s nothing weird or scientific about it. Maximum acceleration requires a low final drive, top speed a high one. And these two terms confuse most. The confusion being the LOWER number denotes a HIGHER gear. Likewise the higher number denotes a lower gear. Likewise the higher number denotes a lower gear. Largely because the lower the ratio, the slower you go and vice versa.

Engine - 1098, Initial Tuning

The 1098 (1100) engine has had a lot of bad press over the years - largely because of early experiences when trying to tune the motor brought about problems with the then standard components available - they simply were not up to taking any real punishment as experienced in racing.

See bottom for useful part numbers.

This fallacy was handed down generation to generation like some scary bedtime story. Those that have used the unit in more recent years, employing more capable componentry know what a demon motor this can be. Following is an initial look at what it will do with a little modification - the results compared directly with it's smaller brother the 998 for illustration of the potential.

Abridged History
When the Mini was first conceived it ustilised a de-stroked version of the then quite remarkable 948cc A-series engine.

Thread Locking Compounds - Application

This is the frequently abused and mis-used stuff dolloped on to bolts/nuts to stop them coming undone. Having seen and heard of many horror stories concerning this stuff, I thought a few words of caution and common sense wouldn't go amiss.

There is a plethora of types on the market with no easy reference as to which to use for what application except in certain cases. Loctite have a very useful guide, their dealers generally able to help with choosing which is best for any given application. The trouble comes when folk buy stuff unwittingly from their local 'do it all' motorist/car spares place. Good stuff is expensive, and it doesn't go all that far. But at least it does its job when used in the correct applications. Unfortunately many buy a cheaper variety with not quite the same application strength, and then apply twice as much hoping it will do the job. It doesn't.

Thread Locking Compounds - Application

This is the frequently abused and mis-used stuff dolloped on to bolts/nuts to stop them coming undone. Having seen and heard of many horror stories concerning this stuff, I thought a few words of caution and common sense wouldn't go amiss.

There is a plethora of types on the market with no easy reference as to which to use for what application except in certain cases. Loctite have a very useful guide, their dealers generally able to help with choosing which is best for any given application. The trouble comes when folk buy stuff unwittingly from their local 'do it all' motorist/car spares place. Good stuff is expensive, and it doesn't go all that far. But at least it does its job when used in the correct applications. Unfortunately many buy a cheaper variety with not quite the same application strength, and then apply twice as much hoping it will do the job. It doesn't.

Gearbox - Fomulae for FD/Tyrespeed and Gear Ratio Calculation

Basic rule to remember is ratio is established by dividing tooth count ondriven gear by the tooth count on its driver. To work out overall gearbox ratios you also have to establish the constant ratio.

Terminology -
FD - Final Drive (diff ratio)

Formula : 60,000 FD (Final drive/diff ratio) x wheel rev per mile.

Calculation for establishing vehicle speed for different final drives.
Formula These are for common tyre types, and accurate enough for assessment - a combination of using industry standard for theoretical calculation, actually measured assortment of wheels/tyres, and calculated averages! Applying

GEARBOX - How they work

Having decided on or even implemented a course of action to bolster the performance of your Mini’s engine, maximising it’s potential should encompass a good look at the gearbox.

GEARBOX - How they work

Having decided on or even implemented a course of action to bolster the performance of your Mini’s engine, maximising it’s potential should encompass a good look at the gearbox.

Clutch plates - Pre-Verto types.

There are generally three types to be concerned with these days - standard pre Verto, fiber rally/race, and sintered race. All at 180mm diameter.

Standard-type plates. The pre Verto plate has a spring-steel centre section to which is riveted the lining. Between the linings are sprung washers. These take up some of the shock impact of engagement and slight surface imperfections of the flywheel and pressure plate surfaces. Providing a genuine Unipart/AP Lockheed one is used, it will cope with most fast road applications without any problems. This includes almost all road-going standard over-bores (+0.020” to +0.060”) and a vast majority of big-bores (1380/1400). That covers up to 110 bhp and/or 90lb ft. - both flywheel measurements of course!! It is the torque that causes more problems than out-right horsepower. It can also be used in the Verto set-up to improve judder/grip/slip problems experienced when using the 'correct' standard plate...

Engine - Metro engine identification data

The widespread and prolific fitment of Metro engines into Minis - usually those endowed as standard with small-bore (850/998/1098) engines - practiced in the UK has been spreading to many other countries worldwide.

So it's not surprising that the most commonly asked question has also become more prolific concerning the fitment of said engine - apart from actually how to manage the transplant and the differences in the installations, covered in articles relevant article on this site - is just which type of engine the individual concerned has bought or what they already have fitted to their car and is it worth keeping or junking. One initial question I pose often draws a pregnant silence whilst said inquiree scrambles their brains trying to find an answer for. Following that protracted pause, 'I dunno' is the usual answer. I then have to get into a lengthy explanation as to how to determine what said engine is.

Engine transplants - Changing FDs and speedo drive ratios.

What they don’t tell you in the manual! Terminology - FD - Final Drive (diff ratio) What they don’t tell you in the manual! If you’ve decided the FD fitted isn’t what you want, changing the FD is possible without separating the engine from the gearbox. Removing the diff case will allow you access to the diff assembly to change the crown-wheel, and access to the gear-change linkage. Use a manual for crown-wheel replacement. While you’re in there it would be just as well to replace the thrust washers and diff-pin as these are the source of many a gearbox problem. Particularly for up-rated engines where fitment for the competition diff-pin is highly recommended. Once again, follow the manual here. Now the bit they don’t tell you how to do... Rod-change types - Removal of the speedo drive housing gives access to the pinion retaining nut (1.5”AF socket needed and a long bar). To be able to undo the pinion nut (torqued up to 150lb ft !!) you need to engage two gears - 2nd and 4th - t

Engine transplants - gearbox information

A subject worthy of an entire book to explain the whys and wherefores, and also causes much consternation on the part of the transplanter. Terminology - BBU - Big Bore Unit SBU - Small Bore Unit FD - Final Drive (diff ratio) A subject worthy of an entire book to explain the whys and wherefores, and also causes much consternation on the part of the transplanter. Much confusion’s spread over which gearbox has the best ratios, is best to use, and with which FD. For a detailed account on this and covering all gearboxes fitted as standard to the Mini, see the relevant separate articles 'Gearbox - Standard production gearbox types'. Fortunately, when selecting a complete engine and gearbox unit from a Metro, the gearbox will pretty much suit the engine and be easily transplantable whole into the Mini. It shares exactly the same rod-change linkage as the Mini. Difficulties only arise when fitting a rod-change gearbox into a pre-1973 Mini that has the old remote-type gear-change mechan

Gearbox - Formulae for FD/tyre size/car speed and gear ratio calculation

Calculation for gear ratios and transmitted engine rpm Basic rule to remember is ratio is established by dividing tooth count on driven gear by the tooth count on its driver.

Basic rule to remember is ratio is established by dividing tooth count ondriven gear by the tooth count on its driver. To work out overall gearbox ratios you also have to establish the constant ratio.

Terminology -
FD - Final Drive (diff ratio)

Calculation for establishing vehicle speed for different final drives.
Formula :                               60,000 
                    FD (Final drive/diff ratio) x  wheel rev per mile.