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 - Common Sources of Problems

Seems recently a number of folk have been suffering gearbox failures of various sorts; nothing new there then except they've popped their heads up over the parapet to ask why. part numbers: C-22A1738, C-22A1731, 88G396, CHM141, 13H9513, 22A611, 22A610, TSP100390, TSP100400, 22G2595 Under closer scrutiny this time around the reasons for bearing failures, gear tooth breakage, and jumping out of gears to name but a few are the sources of hassle. Just like in engine building, a gearbox needs careful and proper attention when building it up. It isn't a difficult job, and most competant DIY mechanics can make a decent job of it. But, just like engine building, it's the knowledge of what to look for prior to and during the build that sets the 'professional' builders apart. Hopefully resulting in a more reliable, perfectly functioning unit. One generally over-looked, or completely missed, feature is where the layshaft is carried in the gearbox casing itself. The shaft merely runs in tw

GEARBOX - Up-Rating Drop Gears

The standard drop gears are fine for practically all road use - almost irrespective of power output. part numbers: DAM9373, C-STR123, C-STR124, C-STR30, C-STR30A, C-STR30T, C-STR30TA, C-STR230, C-STR240, C-STR250 Terminology - Drop Gears - Transfer gears (primary, idler and input gears) Large-bore - Refers to anything based on a 1275-type unit Small-bore - Refers to anything based on 850/998/1098 units Despite what many folk believe - they are more than strong enough, and will perform perfectly well if correctly set up. That means getting the idler and primary gear end floats right, and using new bearings for the idler gear at each re-build. Simply following the methods outlined in the relevant workshop manuals will achieve these simple goals. There are two problems with standard drop gears - the main one is the helical cut of the teeth, the other a very limited selection of ratios. The helical-cut teeth are essentially power absorbing - both from increased metal-to-metal c

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 - Syncro vs 'Dog' engagement

NOTE

; A 'high' or 'low' ratio gear is in reference to it's performance, not it's numerical number. To illustrate - a 'high' FD ratio will give 'higher road speed', but will have a numerically low figure. A 'low' FD ratio will give lower road speed, but have a numerically high figure. part numbers: C-AJJ3371, C-AJJ3319, C-STN39, C-AJJ4014, C-STN76, C-STN77 A by-product of this will be reduced acceleration capability on the 'high' ratio, increased acceleration capability on the 'low' ratio. The main gearbox gears work in the exact same way. Cog swapping 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 (teeth are cut at 90 degrees across the gear as opposed to the angled helical type).

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.

GEARBOX - Close-Ratio Conversion Pre-A+ Gearbox

As outlined in the 'Gearbox - standard production gearbox types' article, it is entirely possible to change the common 4-syncro gearboxes to the helical close-ratio set-up as used in the Cooper S, 1275GT, 1300GT, and some early MG Metros providing the right parts can be sourced. And you don't already un-knowingly have the close-ratio kit fitted! Part numbers are detailed at the end.

The other pre-requisite for this conversion is that it can only be applied to the early, pre-A+ type mainshaft gears. That's those that have the square-topped teeth as supposed to the distinctively pointed A+ profile. This is because despite being endowed with A+-type fittings for the mainshaft end and layshaft, the conversion gears have the pre-A+ tooth profile. This is not to say that the conversion cannot be put into an A+ gearbox casing - it can and is detailed in the relevant article.

What is essential to understand is that the pre-A+ second and third mainshaft gears are going to be

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.

GEARBOX - standard production gearbox types

The first Minis rolled off the production line with a three-syncro gearbox, first gear as explained earlier was still a hit and miss affair.

Terminology -
FD - Final Drive

NOTE; A 'high' or 'low' ratio gear is in reference to it's performance, not it's numerical number. To illustrate - a 'high' FD ratio will give 'higher road speed', but will have a numerically low figure. A 'low' FD ratio will give lower road speed, but have a numerically high figure. A by-product of this will be reduced acceleration capability on the 'high' ratio, increased acceleration capability on the 'low' ratio. The main gearbox gears work in the exact same way.

I’m sure we’re all aware of Sir Alec Issigonis’ brilliant solution to the gearbox location in the Mini - just fold it up underneath the engine, simple. Following is a résumé of the production gearboxes to date.

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.

Engine transplants - Engine to gearbox fitment

Contrary to popular mis-guidance, all BBUs will fit all four-syncro gearboxes. It was only the three-syncro boxes that varied in casting dimensions causing hassles where 1275s were applied to 850/998 gearbox casings.

Terminology -
BBU - Big Bore Unit (1275cc based engines)
SBU - Small Bore Unit (850/998/1098cc based units)
FD - Final Drive

NOTE: This information is largely for transplanting large-bore engine units into small-bore engined Minis. For further information on up-grading transfer (drop) gears, refer to relevant separate article.

Contrary to popular mis-guidance, all BBUs will fit all four-syncro gearboxes. It was only the three-syncro boxes that varied in casting dimensions causing hassles where 1275s were applied to 850/998 gearbox casings.

Engine transplants - Engine to gearbox fitment

Contrary to popular mis-guidance, all BBUs will fit all four-syncro gearboxes. It was only the three-syncro boxes that varied in casting dimensions causing hassles where 1275s were applied to 850/998 gearbox casings.

Terminology -
BBU - Big Bore Unit (1275cc based engines)
SBU - Small Bore Unit (850/998/1098cc based units)
FD - Final Drive

NOTE: This information is largely for transplanting large-bore engine units into small-bore engined Minis. For further information on up-grading transfer (drop) gears, refer to relevant separate article.

Contrary to popular mis-guidance, all BBUs will fit all four-syncro gearboxes. It was only the three-syncro boxes that varied in casting dimensions causing hassles where 1275s were applied to 850/998 gearbox casings.

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.

C-22A1750 KAD GEARLEVER QUIICKSHIFT FOR REMOTE TYPE GEARBOXES

Remote Change

1. Remove original gearstick. Fit Quickstick with original plastic collar, spring and spring retainer, grease well and refit with new spacer. Place flange downwards using longer 5/16” UNC capscrews.

5 SPEED GEARBOX DISMANTLING SHEET

Your 5 speed gearbox has a special 5th gear, laygear, and reverse idler shaft assembled with a modified gearbox main case and a different speedo end casting.

These parts must be removed before the main gearbox cluster can be removed. When a clean work area has been prepared, the removal of the 5th gear and laygear is as follows.

1. Remove the new speedo end casting assembly with the two bearings. These are a slide fit in the casting and are not positively retained.

2. Remove taper bearing No LM11749 off the 5th gear shaft along with the needle roller bearing carrier from the bore of the 5th gear, leaving the gear loose on the shaft.

3. Remove diff and housing as per workshop manual, turn the selector rod at base of diff housing area anti clockwise-and with the spool pull out as far as possible...

A SERIES 5 SPEED GEARBOX - CUSTOMER SELFBUILD KIT FITMENT OF ANCILLIARY PARTS

With the engine and new 5 speed transmission re-installed in the vehicle, the new gear selector parts must be fitted before re-connecting the gear selector extension shaft. The new selector parts can be assembled without removing the gearchange remote from the vehicle. It is recommended that the gear lever be removed....