I was wondering if anyone knew what ratio my gearbox is as it needs replacing, also my gearbox seems to be different than my friends due to his not liking being in 4th at 30 whereas mine does so i want to know if i can find out ratio it is and if its a good ratio to have.
Thanks
Jackman
It basically depends on the year of the car… the 4th gear is infact a direct drive ( via the drop gears which are a 1:1 ratio ) from the crank, therefore the only ratio in the system is the final drive… ( Differential )
Not liking being in forth ( do you mean it’s jumping out or just making a bad noise ) eitherway it is quite likey that the main bearings, in the gearbox, have gone.
The thing you need to get right is the final drive when changing gearboxes.
The most common are…
3.77 - used on 850’s and some vans
3.44 - the most common for Pre A+ mins
3.10 - Used on 12" wheeled Mins.
2.95 - An economy FD
2.76 - Used on Most late model minis
Quick tip, if you engine is original, and you have then engine number this will probably tell you which FD is used in the vehicle..
Post the first part on here…
99Hxxxxxxx
The gearbox is fine on his but his engine struggles to pull the car in 4th whereas mine is fine and will go nicely, my engine number is 99HB81P0142721
Thanks for your help so far.
Jackman
yours is described as…
998cc A+ engines from 1985 on Ungrooved lower main bearings, piston with circlip pin. 42 HP
As no specific diff is detailed would suspect a 3.1 final drive
Guessworks where did you get that information from?
Most information can be found by googling, but ( not that I want to promot any other forum… )
Ratio: 3.11:1 teeth: 59/19 model: City/Mayfair with 12" wheels (1985>)
found that here http://www.ime.org.uk/ime/f/final\_drive.html
what does 3.11.1 mean??
Right here cometh the maths…
3.11 : 1 means that for every 3.11 turns of the engine ( when in 4th ) then the wheels go round once…
Therefore using the the standard tyre 145/70x12 ( or for that matter 165/60x12 as the rolling distance is only a mm or so different ) approx 1595mm
so to workout the speed for a give engine rpm, use the following
( engine rpm / 3.11 ) * 1595 * ( 60 / 1609344 ) = mph
1609344 is the number of mm’s in a mile and 60… minutes in an hour !
so… at 3000rpm
( 3000 / 3.11 ) * 1595 * ( 60 / 1609344 ) = 57.3 mph
bluddy hell ur good at maths lol
Bloody hell!! Thanks for that, its helped me alot.
:nugget:
:worship:
i reckon we should get rid of that man holding the flag thoing and put a pic of gessworks there..
i remember doing that stuff at college but i would never be able to remember it like the way you just put it,
well done!
