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DIY Classic Mini Gearbox Articles

GEARBOX - Close-Ratio Conversion A+ (Calver's Corner)
GEARBOX - Close-Ratio Conversion A+ 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 ...
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22G2026MM Rod Change Shifter Conversion Bracket (Technical Information)
Procedures Align the holes in the red wooden locating blocks with the holes in the bracket and tape or glue the blocks to the bracket. Attach bracket, with locating blocks attached, to the gear lever housing and raise the housing until the locators touch the tunnel. Drill two 5/16” diameter holes through the tunnel at the spots marked, using the bracket and locating blocks as guides....
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C-AEA3240 - REPLACEMENT FULLY-FLOATING PRIMARY GEAR BUSHING (Technical Information)
  FOR 1275-TYPE PRIMARY GEARS ONLY  To eradicate the hassles caused by primary gear front bushing seizure/wear, this bush has been developed to be a straight replacement with no post-fitment corrective size machining required.   In race use, the bushing can become seized/partially seized on the crankshaft, spinning the bushing the primary gear journal and usually preventin...
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Center oil pick-up pipe C-AHT54 (Technical Information)
FITTING INSTRUCTIONSOil pressure loss caused by oil surge can be experienced under hard cornering. To alleviate this it is essential to fit a centre oil pick-up pipe. Mini Spares' continual research and development program has seen advances in pick-up pipe design, replacing the original ancient design conceived by Abingdon ST some thirty-plus years ago. The finer gauze (as used in many oil sys...
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Classic Mini Gearbox Rebuild - Mini Mania Video (Technical Information)
Classic Mini Gearbox Rebuild Gearboxes may seem complicated but they are very simple in their construction, and surprisingly easy to put together. The main issues are having the right tools to do the job. So here's a list of what you will need: Torque Wrench with a maximum range in excess of 150lbft 1 1/2″ deep socket ( a ball joint socket is ideal ) Small ratchet and a long...
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ENGINE TRANSPLANTS - gearbox information (Calver's Corner)
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 ...
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GEARBOX - Close-Ratio Conversion Pre-A+ gearbox (Calver's Corner)
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 ...
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Gearbox - Common sources of problems (Calver's Corner)
 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. 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 need...
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GEARBOX - Final Drives, standard (Calver's Corner)
The final drive gears are ultimately responsible for the way your Mini goes after engine, gearbox, and under carriage tweaking has been applied. 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 ...
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GEARBOX - Formula for Final Drive calcualtions (Technical Information)
Calculation for establishing vehicle speed for different final drives. Formula :                               60,000                      FD (Final...
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GEARBOX - How they work (Technical Information)
SHOP GEARBOXES and GEARBOX PARTS   GEARBOX - How they work       click on links for related images      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. It rarely does, as most folk take one look at those seemingl...
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GEARBOX - Limited Slip Diffs, What they're about. (Calver's Corner)
Terminology -LSD - Limited Slip DifferentialModified engines producing more power generally induce owners to drive with greater verve, particularly when competing in one of the many motorsport disciplines. 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 determi...
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GEARBOX - Limited Slip Diffs, what's available. (Technical Information)
Terminology - LSD - Limited Slip Differential   ‘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. The ‘Salisbury’ was designed in the ‘50s at a time when racecars were a good deal less sophisticated than today. Ty...
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GEARBOX - Limited Slip Diffs; necessary parts for installation. (Calver's Corner)
  Terminology -   LSD  - Limited Slip Differential   CWP - Crown Wheel and Pinion   FD    - Final Drive   Fitting an LSD isn't as simple as replacing the diff cage unit. In all cases a certain degreeof diff housing modifications is needed - material needing to be ground/filedaway to provide clearance for larger diff housing cases and ...
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GEARBOX - standard production gearbox types (Technical Information)
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.  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. The spee...
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GEARBOX - Syncro vs 'Dog' engagement (Technical Information)
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...
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Gearbox - Up-rating diffs and FDs. (Technical Information)
Terminology - FD              - Final Drive/diff ratio LSD           -  Limited Slip Differential Drop gears - transfer gears (primary, idler, and input gears)   There’s a good selection of straight-cut final FDs available. Examine the FD table, and using informa...
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GEARBOX - Up-rating drop gears (Technical Information)
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 The standard drop gears are fine for practically all road use - almost irrespective of power output. Despite what many folk believe - they are more than strong enough, and will perform perfectly we...
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Gearbox Rebuild (Technical Information)
Gear Box Rebuild  Written By GuessWorks Gearboxes may seem complicated but they are very simple in their construction, and surprisingly easy to put together. The main issues are having the right tools to do the job. So here's a list of what you will need. SEE VIDEO HERE Torque Wrench with a maximum range in excess of 150lbft 1 1/2" deep socket ( a ball joint socket is ideal ...
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How do I know which transmission my Mini has? (Technical Information)
It’s really quite easy to tell which generation of gearbox, shift linkage, and axle your Mini has.  Let’s say you want to order a replacement but terms like “remote”, “rod-change”, or “pot-joints” have you a little befuddled about just what the heck to order!  Let’s very simply describe the three styles  used in the production of...
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Idler gear - Setting end float (Calver's Corner)
A fairly crucial part of how the idler gear operates is its tolerances and running clearances. End float is a continual problem as folk either ignore it through ignorance or lack of accessible information on how to do it, or belief special tools are needed. Also, later factory assembled engine units (from about 1992 onwards) were built up using whatever shims and thrust washers were available, sin...
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LSD Design (Technical Information)
Mini Mania is the sole US representative of the excellent "Evolution" differential. Basically a clutch type diff, it is a 1950's ideal incorporating a 1990's technology. It is much more refined than the previous plate type diffs. Modern engineering and design allows cariations in static pre-load, percentage torque transfer and accelleration/decelleration action to be made. This f...
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Magnetic oil trap, C-2A3637 (Technical Information)
         Installation of this kit involves opening and re-sealing the oil suction passage. Improper sealing can result in low (or no) oil pressure and subsequent engine failure. Always observe the oil pressure warning light/oil pressure gauge when starting the engine after installation of the kit or re-installation of the magnetic plug ...
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Mini Idler Gear- 4 sync 22G943 (Technical Information)
Idler gear shimming You need to check the clearance before you mount the engine. Here's how: Insert the idler gear with the thrust washers it came with into the gearbox. Bolt the end casing in place with the gasket. Tighten to the spec torque. Measure the idler gear float with a feeler gauge. It should be ~0.003". If it's more than that, a...
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New design of C-AHT54 Central-oil pick-up pipe - the reasons why. (Calver's Corner)
Terminology - COPUP - Central Oil Pick Up Pipe For years there’s only been one type of COPUP commercially available, but recently Mini Spares has seen fit to produce a new and much improved version. This initially caused much apprehension as it was a far cry from the original Abingdon 'ST' design Perhaps the most voiced question was 'Why? Isn't this a case of if it ain't broke don't fix it?...
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Phantom Grip LSD Installation Instructions (Technical Information)
PHANTOM GRIP LIMITED SLIP DIFFERENTIAL CLASSIC MINI BASIC INSTALLATION INSTRUCTIONS KIT INCLUDES 2 DISC PLATES, 4 GOLD SERIES SPRINGS, INSTRUCTIONS, AND 2 STICKERS Click photos for larger image   STEP 1: TOOLS NEEDED: HAMMER, DOWELL REMOVER, WRENCH SET, TABLE PRESS, T...
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PRIMARY GEAR - Bush problems (Calver's Corner)
Although not of immediate interest to many road-runners/street-burners, mainly accorded to the racing scene, it seems to be a perplexing problem to a very large number of folk around the world, and has burned up plenty of telephone time. Distilling the myriad of ‘the symptoms go like this’ descriptions down from various languages it has been put to me in – the end result was ...
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Primary Gear - Bush Replacement (Calver's Corner)
See bottom for useful part numbers. With the cost of new primary gears spiralling ever upwards, and the availability of good, serviceable used ones, fitting new bushes to existing gears is becoming a more common solution. For some reasons for bush failures and rectification to stop it re-occurring, see article Primary gear - Bush problems. Since there is no useful information given in any of the w...
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Pros and cons of Limited Slip Differentials (Technical Information)
Evo (Trannex) 1950s design with 1990s engineering and technology - originally done by the inimitable Davc Hirons at Trannex, now under the EVO banner at Mini Spares Centre following their buy-out of all the Mini/Sprite Trannex products some years back now. The only real similarity to the old Salisbury is the 'plate type' design - purely because it gives maximum frictional area, therefore most e...
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Putting Our Mini's Transmission Back Together (Restoration)
Putting Our Mini's Transmission Back Together December 19, 2012 Our Mini needed some transmission love  Mini Mania owner, Don Racine inspects our Mini's gearbox internals Our gearbox came out perfectly  When we bought our car, the engine and transmission were pretty much completely disassembled. While there isn’t much on an old British car that ...
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Quaife Limited Slip Differentials (Technical Information)
The Quaife torque biasing differential enables your car to accelerate quicker and corner faster. How? By getting the power to the ground! The Quaife Differential powers both drive wheels under nearly all conditions, instead of just one. With an ordinary open differential, standard on most cars, a lot of precious power is wasted during wheelspin under acceleration. Thi...
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Quick Shift Kit, Remote & Rod change type, C-22A1750 & C-22A1751 (Technical Information)
REMOTE CHANGE 1. Remove original gearstick. Fit KAD 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. ROD CHANGE 1. Remove original gearstick assembly and using molewrench, remove two dowels from top of diecast gearchange housing. 2. Fit aluminium bell to top of gearchange housin...
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Rebuilding the Shifter Mechanism (Restoration)
Rebuilding the Shifter Mechanism Febuary 13,2013  Our shift mechanism is now rebuilt with original style boot & knob from Mini Mania Left to right- Early, mid & late shifter designs. Found on the back of your transmission.  The insides of shifter housing were   simple. Just required some clean-up. There are three type...
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Synchromesh Transmissions vs Dog engagement (Technical Information)
Synchromesh Transmissions Most modern cars are fitted with a full synchronized engagement gearbox. This relatively old design concept assure the delivery of smooth, reliable, and quiet operation.  This is an absolute must have for any car that is a daily driven vehicle. Synchromesh transmissions operate using a special collar that applies force to a cone-shaped area attached to the gear. The...
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