Hi all
I have found out what my diff ratio is but would like some feedback on the process I used.
As I don't have a tachometer or an accurate speedo and didn't want to pull the engine I did the following.

With the car in 4th gear and jacked up on one side I can turn the wheel and with an indicator on the distributor rotor I could count how many times the distributor rotates. Easy
Because you are only turning one wheel the differential will halve the ratio !
Because I measuring at the distributor it rotates at half the engine speed !
So, if I turn the wheel 4 full rotations, i (or in this case the wife) could count the number of rotations of the distributor and I would have exactly the diff ratio

Indicator marked in 18 degree segments (0.05 of a rotation).


The wheel marking point to count its rotations.


4 wheel rotations gave me 4.15 rotations of the distributor so I have a 4.15 to 1 ratio, right
Are my assumption correct

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Find a job you love and you will never have to go to work !

Try it again but with the car on the ground and push it in 4th gear.

Then it should only be 2 rotations of the wheel to allow for the half speed of the distributor right

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Find a job you love and you will never have to go to work !

Just wheeled along the driveway and two wheel rotations gave 4.05 at the distributor so allowing for parallax error both results are pretty close to each other.

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Find a job you love and you will never have to go to work !

The nearest diff ratio to that would be a 4.1.
Which is a fairly useless road diff in a Mini.

Useless is an understatement.
I'm considering something around 3:1. It is an 1100S so it should pull that OK I think.

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Find a job you love and you will never have to go to work !

Mates runs a 3.1 in his cooper s and it still goes really well.

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I can't comment on how to find your current diff ratio but I do have a 3:1 in my car and I love it. It still has good acceleration and is great on the highway.

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Respect mine and I'll respect yours.

4th gear is 1:1 so whatever your diff ratio is will be 2 x the dizzy rotation since the dizzy rotates at half the engine speed!

With the car in 4th gear and the road wheel turned 1 revolution, the dizzy should have turned 2.05 times for you 4.1:1 diff ratio yeah?

Cheers Shane

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If it's not a Cooper S, the mini was designed to be modified!

Thanks Bubbacluby, Kennomini & MiniVLT for the info on diff ratios.
I'll have to chase up a 2.95:1 or a 3.1:1.

Phil

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Interesting outcome ...hope you pulled the plugs before pushing in 4th

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"Show me the Mini!"

Why? It will push quite easily in 4th.

Oh sorry Mike, didn't allow for your clapped-out, needs new rings, lots of blow-by, low compression engine

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"Show me the Mini!"

Yes, pulled the plugs otherwise I might've needed a new ring

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Find a job you love and you will never have to go to work !

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.