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1275 auto into minimatic?
https://ausmini.com/forums/viewtopic.php?f=5&t=88405		 Page 1 of 2
Author:  Garagedefend [ Fri Jan 23, 2015 1:20 pm ]
Post subject:  1275 auto into minimatic?
hey all, I've got a 998cc minimatic at the moment. Goes alright but I would just like a bit more go to keep up with traffic atleast.

I have someone with a 1275 auto block for sale.

I imagine gearing wise it would be the same? so it'll get to 80kph faster but still be screaming its head off at 100?

or is there also an alternative gearing available for an auto box?

and can the auto boxes take a slightly hotted up car? basically just want a better exhaust and maybe carb but its just for putting around town so not extremely fussed. Maybe just exhaust as its got a leak anyway.
Author:  peterb [ Fri Jan 23, 2015 2:01 pm ]
Post subject:  Re: 1275 auto into minimatic?
There's a 2.760:1 ratio, but their availability, I don't know
Author:  simon k [ Fri Jan 23, 2015 2:12 pm ]
Post subject:  Re: 1275 auto into minimatic?
Greig Malure's girlfriend drives a 'matic with a 1275 stroked to 1430 and it's got a lot of grunt
Author:  9YaTaH [ Fri Jan 23, 2015 2:18 pm ]
Post subject:  Re: 1275 auto into minimatic?
3.1:1 would be good...or with more power 2.9:1...but will all manual diffs go into a slush box?
Author:  Garagedefend [ Fri Jan 23, 2015 2:26 pm ]
Post subject:  Re: 1275 auto into minimatic?
I'm under the impression they didnt. Or maybe its just the motor/box itself hence needing an acutal auto 1275.

Thats a good option then I suppose. 1275 stroked to 1430 on an auto. Is he on the forum? would love to find out a little more about it.


if you can change the diff ratio out on an auto that would be good then. Atleast I can sit on a highway and not have it screaming its head off
Author:  drmini in aust [ Fri Jan 23, 2015 5:57 pm ]
Post subject:  Re: 1275 auto into minimatic?
The diff ratio in an 1100S (or Minimatic) autobox is 3.26 it is true, but... the drop gear ratio is only 1.15:1, not 1:1 like a manual is.
sooooo... the overall ratio is only 3.76:1. NOT 3.26.

They tend to scream their tits off with 10" wheels, I used to own a `Matic with an 1100S auto in it.
Not much you can do except put big wheels on.. a manual crown wheel and pinion do NOT fit an auto.

As for the comment above about Greig Malaure's 1430 Matic, it only did around 18secs at WSID when it ran there on the ausmini night drag. Had 112HP crank HP then on the engine dyno I believe. Hard to get off the mark due to the low stall speed of the converter.
Author:  Garagedefend [ Fri Jan 23, 2015 9:34 pm ]
Post subject:  Re: 1275 auto into minimatic?
Can you fit any taller gears At all? I'd really like to keep the 10s.

Otherwise a built motor will only get it to screaming point much quicker hahaha
Author:  Kennomini [ Fri Jan 23, 2015 9:49 pm ]
Post subject:  Re: 1275 auto into minimatic?
Can u change the drop gears or is it just the Morris 1100's that had the 1.15:1 :?:
Author:  drmini in aust [ Sat Jan 24, 2015 9:04 am ]
Post subject:  Re: 1275 auto into minimatic?
Nope the drop gear setup is completely different to a manual box. Even the primary gear and its splines are different. Nothing interchanges.
The diff pinion and crownwheel setup is much bigger, and different pinion splines too.

I dunno what ratio the late Rover autoboxes were, perhaps they had taller gearing? :?
Author:  Garagedefend [ Sat Jan 24, 2015 9:25 am ]
Post subject:  Re: 1275 auto into minimatic?
never driven an auto rover box. Are they of the same idea though? as in no actual computer to control the gearbox?

I suppose as a worst case I can just go 1275 and keep the box I've got in it and just stick to 80/90 and 100 when needed. I cant go fast but atleast I wont be slow LOL its mainly when going from a stop and going uphill
Author:  drmini in aust [ Sat Jan 24, 2015 11:48 am ]
Post subject:  Re: 1275 auto into minimatic?
Rover auto box is much the same inside, except it has been re-engineered to have a Park position. Which MiniMatic and 1100S auto did not.
Some bearings etc for all these boxes are now unobtainium.

I'd stick with a manual... they go harder. :wink:
Author:  Garagedefend [ Sat Jan 24, 2015 8:38 pm ]
Post subject:  Re: 1275 auto into minimatic?
I suppose I should just teach my wife to drive manual when this motor packs it. Box was rebuilt in 2002 tho
Author:  9YaTaH [ Sun Jan 25, 2015 6:27 pm ]
Post subject:  Re: 1275 auto into minimatic?
drmini in aust wrote:
The diff ratio in an 1100S (or Minimatic) autobox is 3.26 it is true, but... the drop gear ratio is only 1.15:1, not 1:1 like a manual is.
sooooo... the overall ratio is only 3.76:1. NOT 3.26.

They tend to scream their tits off with 10" wheels, I used to own a `Matic with an 1100S auto in it.
Not much you can do except put big wheels on.. a manual crown wheel and pinion do NOT fit an auto.

As for the comment above about Greig Malaure's 1430 Matic, it only did around 18secs at WSID when it ran there on the ausmini night drag. Had 112HP crank HP then on the engine dyno I believe. Hard to get off the mark due to the low stall speed of the converter.


Bugger! (ooops I mean "bother")
Author:  Morris 1100 [ Sun Jan 25, 2015 6:38 pm ]
Post subject:  Re: 1275 auto into minimatic?
They built thousands of automatic Minis right up to the very end.
Just get a late motor, stick it in your car and enjoy.
Author:  850man [ Sun Jan 25, 2015 6:48 pm ]
Post subject:  Re: 1275 auto into minimatic?
I fitted a 1275 Auto to the President of the VMCI mini recently. It goes very well.
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