I've acquired a thin flange 1100s (1275) motor.
Do they come with a 3 syncro or 4 syncro box.
And what ratio would the diff be?
Thanks guys.

3 synchro.
Diff is 4.13, I think..
They had 12" wheels & high profile tyres.

You would want a 3.44 to go in a Mini.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

They came with the three syncro box.
Diff ratio was either 3.765 for the 12Y motor and 4.133 for the 12YD motor.

It is not unusual for things to have been changed since they left the factory though.

Thanks guys.
The motor was taken directly from a Morris 1100 so it's probably unchanged.
I'll check tomorrow for the engine number.
I want to avoid the "goin' for 5th gear" feeling I used to get with the 1100 motor.
The S motor will get a small amount of work before it goes in, so if it needs a slightly taller diff now's the obvious time to do it.
Ps. It'll be going in the MG

That's what I have in my van with a 3.44 diff and 10 inch wheels. Also changed the input and laygear to 3 synch Cooper S type for better ratios.

The remote gearchnage has a sandwich plate which attaches to the diff housing - different from the Mini housing. It was supposed to reduce vibration on the more 'upmarket' 1100 models, but I can't discern any difference.

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Slide
1965 Mini Van (1360)
1970 Mk2 Cooper S (1310)
1978 Rover SD1 V8 (4.6)
1996 Land Rover Discovery V8 (4.0)

The engine No is 12YD/Ta/H5***
So it looks like its got the slow diff.
What would the standard diff be for the 1100 that's in it?

An MG 1100 should probably have a 4.133 diff.

We used a 3.647 in Morris 1100's 1100S stroker and he says it goes like a train.
Plenty of this ratio about, I have 1 or 2 here.
3.765s are easy to find too, any Mini Deluxe or 850 has one.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

What is a good cruising RPM for a 1275 at about 100k?
And I take it that to change ratios, the gearbox needs to come apart?

You have done very well. I would have thought you would have had to change more than just the input and laygear to get the 3 synch cooper S ratios

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" A Hundred Years From Now It will not Matter what my Bank Acount Was,
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