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DIY Classic Mini Gearbox Articles
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GEARBOX - Close-Ratio Conversion A+
(Calver's Corner)
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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)
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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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Center oil pick-up pipe C-AHT54
(Technical Information)
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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)
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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 lon...
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GEARBOX - Close-Ratio Conversion Pre-A+ gearbox
(Calver's Corner)
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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)
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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 gearbo...
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GEARBOX - Final Drives, standard
(Calver's Corner)
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Terminology -
FD - Final Drive/diff ratio
FDs 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 in...
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GEARBOX - How they work
(Technical Information)
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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 seemingly formidable teeth and decide it's not for th...
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GEARBOX - Limited Slip Diffs, What they're about.
(Calver's Corner)
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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)
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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 - standard production gearbox types
(Technical Information)
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New Page 1
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 capabilit...
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GEARBOX - Syncro vs 'Dog' engagement
(Technical Information)
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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 ca...
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GEARBOX - Up-rating drop gears
(Technical Information)
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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)
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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 )
S...
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Idler gear - Setting end float
(Calver's Corner)
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Terminology: DTI - Dial Test Indicator
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 sh...
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LSD Design
(Technical Information)
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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)
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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)
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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)
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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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PRIMARY GEAR - Bush problems
(Calver's Corner)
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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)
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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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Quaife Limited Slip Differentials
(Technical Information)
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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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