Hi All

I'm new here and just after advice as I have a mk 1 morris mini cooper s, which has been sitting in the shed for over 20 years and now hopefully will progress towards having it road worthy. It has a straight cut gearbox and wanting to change it to a cooper s box. I have been offered a morris 1100 s engine and gearbox, what difference is there between 1100s box and cooper s?

Hope some one can advise or direct me to a link which may help. There seems to be a wealth of information here.

I'll move this to Mini Chat.

Your Mk1 will have a 3 speed synchro gearbox if it remains original.

The 1100s gearbox will come over, however the ratios will be different to a mk1 or 2 Cooper S gearbox. Broader steps between gears. The diff ratio will also be different. Depending on the gearbox type, it may also be a 4 synchro gearbox as well.

You would need as a minimum a laygear, 1st motion shaft as well as differential to create a close ratio Cooper S gearbox.

Your mk1 gearbox will be worth more than a few coins as well, just for the case on its own if it is the correct cast-in part number.

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SooperDooperMiniCooperExpertEngineering

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

The final drive could be different IE rubber Vs hardy spicer. The gear selection is a little different too. The selector must be used with the relevant g'box. Not interchangable.

EDIT: yes, remote shifter is different

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The bitterness of poor quality (or Crappy Workmanship) remains LONG AFTER the Sweet Taste of Low Price is forgotten.

Not sure what you mean by `selector'... (remote shift housing?)
The diff housing and remote shift housing of the 1100S are a bit different design to those on a Cooper S. There is a rubber sandwich plate between them and the 4 bolts are horizontal, not vertical.

It is possible to fit a Deluxe/S diff housing to an 1100S box then use the S remote shift, but the diff bearing housings need checking for size and alignment when bolted up. Some machining may be necessary, or the 2 dowels may need to be left out. But yes it has been done successfully many times in the past. I did one last year.

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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.

I've got an 1100 S box in my 1360 van. With a 3.4 diff the gear ratios were not ideal on 10 inch wheels, so I swapped in Mk1 Cooper S (3 synchro) 1st motion and laygear.

Doc is correct about the rubber 'sandwich plate' on the back of the diff housing, you need to use the 1100 remote, or change the housing to a Mini type. The rubber was supposed to dampen vibration but I'm not so sure it does anything much.

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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)

If you want to use the 1100 remote you can burn the rubber from the sandwich mount, and weld it up with a steel spacer in there to make it solid.

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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.

Thank you for the reply's. The gearboxes on the 1100s engines were they all 22G333? From my research there were two types of engines installed into the Morris 1100 s, one had bigger crankshaft journals to the other.

Can some one advise of the engine numbers and what are the physical differences.

Early 1100S had Cooper S rods and 1.625" big end journals.
Later one had HEAVY! rods with lumps on the caps and 1.750" big end journals.
You can confirm which you have by peering into the fuel pump flange hole.

Changeover was engine # 12YD/Ta/H10487/10488

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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.

If You do fit an 1100 S gearbox to your Mini I would suggest that You use the transfer/
Clutch Housing as well. because they are different, the locating dowels are a different size,
I am not saying it cannot be done just that You should be aware of it
As far as I know apart from the Automatic the 1100 S is the only one that
the transfer housing was machined to match the gear box case
Dr Mini Kev, may wish to comment on this

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" A Hundred Years From Now It will not Matter what my Bank Acount Was,
The Sort Of House I Lived in, Or The Kind Of Car I drove ... But The World May Be A Better Place
Because I was Once Important In The Life Of A Child"

John is correct, I have had to machine 1100S dowels down by 1/16" on one end a few times to use an 1100S box with a Mini flywheel housing or vice versa.
Mini dowels are 3/8" dia and 1100S ones 7/16", from memory.

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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.