mk1-forum.net

Underbonnet photo of the first automatic Mini prototype in 1962



In 1965 the world's smallest automatic gearbox arrived, specially developed by Automotive Products. All parts were housed in the sump and uniquely lubricated by circulating the engine oil. Announced in 1965 but because of many problems only became available in quantity from 1967 making Mk1 versions very rare. Early testing revealed that oil surge in the sump under cornering could cause oil starvation of the torque converter and sky-high engine revs. To compensate for this failing the oil pump was moved to the centre of the sump and oil capacity was increased.

Final assembly problems also arose and manufacture of the gearboxes was transferred to clinically clean, dust free rooms to ensure a dependable assembly of the unit with its numerous hydraulic valves.

The design itself put all known hydraulic boxes in the shade and to make the most of the engine's meagre output, gave four speeds as against the three of other automatics current at the time.

A mechanical control ensured gear selection according to load when in automatic mode, and there was also a kick-down working directly off the throttle pedal. To compensate for the usual auto power losses on an 850cc, the compression ratio was increased to 9:1 and a larger SU carburettor with inlet manifold was fitted. (I can remember searching for the auto Mini's in scrapyards in the 1970's to aquire these parts for upgrading our 850cc manual cars!)

Useful AP Automatic Technical Information:
http://members.tripod.com/austin_america/id72.html


Mini-1100 AP Automatic Transmission:
http://www.austinmemories.com/styled-105/index.html

Automatic Mini Register:
http://autominiregister.proboards.com/

Great BMC Pathe film on factory build of the Mini/1100/1300 Automatic Gearbox (sadly no audio/sound)
Automatic Transmission And Power Units (1967)
https://www.youtube.com/watch?v=ieraaVfUs4Q

Wow...that looks very different from the final version.

Didn't realize they were that "rare" ( MkI's )
A girlfriend had a MkI auto 850 years ago...was an original export to CA.

Just been told by an ex-BMC/BL worker apparently there was a man in Longbridge who's sole and only job was to mate 7 A-series engines and AP autoboxes together each and every day!

I know that when compared to modern automatic boxes the Mini auto transmission is very primitive, but for its time it was an absolute marvel! Much more refined than most other boxes on the market & most amazingly, practically unchanged from its introduction to the end of Mini production. It started off under 850's & ended up under 1300 MPI's.

Was there really an automatic MPI ?
I always thought the MPI block was manual only.

Not sure if the MPi and SPi blocks are the same, I thought the late ones were but this is an SPi on top of an auto. Japan market.
https://page.auctions.yahoo.co.jp/jp/auction/h410114701

Thanks. Looks like that is as far as the automatic gearbox went?

Japanese spec Mini 40 was a hybrid using the MPI block but fitted with single point throttle body and the other pre-MPI ancillaries.

I’ve never seen or heard of an actual MPI automatic mini. Did it exist?

mk1 wrote:I know that when compared to modern automatic boxes the Mini auto transmission is very primitive, but for its time it was an absolute marvel! Much more refined than most other boxes on the market & most amazingly, practically unchanged from its introduction to the end of Mini production. It started off under 850's & ended up under 1300 MPI's.

Really, until the advent of advanced electronics in auto gearboxes, this one was way ahead of it's competition, even including a 'tow start' pump until they had to incorporate a Park position late in it's time. With regular Oil Changes, they lasted reasonably well too. The guys who developed it really did an amazing job.

iain1967s wrote:
I’ve never seen or heard of an actual MPI automatic mini. Did it exist?

Yes, they certainly did an MPI Auto - I have a block from one here. The Auto was available right to the end of production in 2000.

When they were developing the gearbox, AP said they could have made it a 5-speed!

-But it was already unique, being 4-speed, and the smallest-engined automatic at the time...

The only problem was sharing engine oil, and that's why they don't last. The 1800/2200/Princess was better as the engine and gearbox oil were separated. They used a 3 speed Borg Warner 35.

andy1071 wrote:When they were developing the gearbox, AP said they could have made it a 5-speed!

-But it was already unique, being 4-speed, and the smallest-engined automatic at the time...

About a year ago I got asked by one Mr Quaife to supply an auto box for their museum

Turns out he had developed a 5 speed sequential box many years ago and even a 6 speed , but they needed to be fitted in an auto casing

Waits for sound of forum members scuttling off to Quaife....

I talk to a local dog walker who worked at AP as their Technical Publicity Manager he was there for 12 years until the accountants took over .. his AP company car was a Cooper S with Auto. also told me the Manager of the AP Development Shop rallied a Auto Box Cooper S.
Hope more info comes out as the Dogs get Walkies.

Keith Gerrard and the 5-speed AP Auto box...."a little known part of BL history that deserves to be more widely known."

"There was a much altered and uprated 5-speed (instead of 4-speed) AP1 Mini Automatic gearbox developed by Keith Gerrard of Bushey Transmissions in conjunction with Jack Knight, which was fitted with a clutch with extra radial shock springs in place of a torque converter and an electronic shift mechanism."



Details and comments below are from Keith Gerrard posted in a thread on the Autosport forums:-
https://forums.autosport.com/topic/1446 ... was-worst/




The article below is from the September 1979 issue of Cars and Car Conversions in which an early development of Keith Gerrard’s Mini Hot Rod auto box was tested.




Another article below from CCC about the Midas rally car equipped with the Gerrard Auto based on the AP transmission.

Tim Harber wrote: ↑Sat Aug 31, 2019 11:31 am

About a year ago I got asked by one Mr Quaife to supply an auto box for their museum

Turns out he had developed a 5 speed sequential box many years ago and even a 6 speed , but they needed to be fitted in an auto casing

Waits for sound of forum members scuttling off to Quaife....

When Steve Harris shut down his shop years ago he held an auction and had two of those boxes.

As you say they were in auto cases with a big billet front plate with Quaife machined into them and many fancy gears inside.

Foolishly I didn’t buy those or the twin cam 970 engine he’d built but we have still got a vast quantity of seals and gaskets from him.