13 replies to this topic

[Msmith3327]

Not really a problem, more of a hmmm i wonder.

I have been told that some Mini's had a higher final gear ratio which gave them a higher topspeed, is this correct. I used to have a 1990 city 998 with no modifications that used to go like a bomb in fourth gear 90mph. I now have a 1989 City that wont go over 75mph with a stage 1 kit fully tuned.

Is the gearbox rummor true????

[Ethel]

If it takes 70bhp to do 100mph (not saying it does, but probably not too far off) and your engine produces 70 horses at 6500rpm then you need a drive ratio that matches the 2 up. Too low a ratio and you'd run out of power to accelerate to 100mph: too high and you'd run out of revs (go past the engine's max power band).

guessworks has a gear calculator on his site and you could play around with Winsu (free download)

[Msmith3327]

Thanks Ethel, i dont want to do any internal changes, was wondering more if any standard Mini gearbox's were different and ran different final gears.

[Ethel]

there are masses of options, again GW's site has good info.

Yours are likely to be 3.1:1 as cities on 12 inch wheels

Thanks Ethel, i dont want to do any internal changes, was wondering more if any standard Mini gearbox's were different and ran different final gears.

[Msmith3327]

That is a very interesting and helpfull site Ethel, here is another question after reading through it. The car was originally an automatic and was converted to manual by the prev owner.

The question is.

Should they of adjusted or replaced anything to do with the speedo when changing the gearbox, if so how can i tell if they have put the right bits in.

[Ethel]

Thank John for the site - he's on TMF too.

his site also has good info on speedos (mph not budgie smugglers). The simplest check would be to compare the mileage over a known distance.

That is a very interesting and helpfull site Ethel, here is another question after reading through it. The car was originally an automatic and was converted to manual by the prev owner.

The question is.

Should they of adjusted or replaced anything to do with the speedo when changing the gearbox, if so how can i tell if they have put the right bits in.

[taffy1967]

Nothing happened to the gearboxes on either a 1989 or a 1990 Mini City and so you should be getting the same performance from your current Mini.

When the Mini City was known as the Mini City E (just prior to 1989), it did have a higher gear ratio (2.7 or 2.9 perhaps?) instead of the more common 3.1.

[Ethel]

I'm pretty sure the City/city E had 2.95 on 10 inch wheels and 3.1 on 12's.

Nothing happened to the gearboxes on either a 1989 or a 1990 Mini City and so you should be getting the same performance from your current Mini.

When the Mini City was known as the Mini City E (just prior to 1989), it did have a higher gear ratio (2.7 or 2.9 perhaps?) instead of the more common 3.1.

[taffy1967]

I'm pretty sure the City/city E had 2.95 on 10 inch wheels and 3.1 on 12's.

You're probably right, but the 1984 Mini 25LE had the 2.95 gear ratio which was the same as the Mini City E. That and the Mini Mayfair got 12" wheels and discs up front as standard from October 1984.

I always assumed that the City E retained the 2.95 gear ratio until it switched to being just Mini City in October 1988.

Either way the 1985 Mini City E and 1988 Mini Mayfair I once owned happily cruised along at 70mph.

Edited by taffy1967, 18 May 2010 - 03:04 PM.

[MiniBonkerz]

i was wondering how would a mpi on 10's perform with standard box ? ie will it run through gears faster and loose top speed or other way round?

[Msmith3327]

Sorry but being dim i dont get all this 2.9/3.1 stuff, In short if i were to get a second hand gearbox, which one would have a better final drive ????

[Guess-Works.com]

There are numerous final drives, both related to different models of mini but also metro's, buying a second hand gearbox can be a bit of a lottery for which final drive it has in it..

[Cooperman]

To explain a bit more. The higher the number of the final drive, like 2.9, 3.1, 3.44, etc, the lower the final drive gearing. So, with higher numbers it will be going slower at a given RPM.
Now, for best acceleration, you need a higher number final drive ratio (known as a LOW diff ratio), but for long distance steady cruising a lower number diff, giving a HIGH diff ratio is often used although this will reduce the acceleration.
You won't gain any more top speed with a higher diff ratio, as has already been said, and you can gear the car so high that it won't pull up to maximum power in top gear due to the gearing.
As for what gearing you'll get with another box, the only way is to count the teeth on the crownwheel and divide that by the number of teeth on the pinion. That will give the final drive ratio.
Ideally for your car a 3.1 or 3.2 is probably best.
You can't just guess what ratio you might have as the manufaturers used so many different ratios over the years on different models.

[Msmith3327]

Cheers cooperman, that cleared that up.