How did early Automatic gear boxes on cars work?

[Dave HalfordParticipant @davehalford22513]

Posted by Bruce Voelkerding on 06/06/2023 13:04:02:

this was in the States, out in the Country. We had a '63 Ford Galaxie, color Light Blue, which developed a strange Problem in 1968. Sometimes, not always, it would burn "Oil" and leave a blue Cloud behind it like a war-time Smoke Bomb. Us Kids thought it was fantastic – naturally we named it the "Blue Streak". It was odd that it was an intermittent Phenomena. Even more odd, there was no detectible loss of Engine Oil Level. It dawned on me one Day to check the Automatic Transmission Fluid. It was quite low, so it went to the Ford Shop.

I remember the Repair Cost was surprisingly low. They had replaced something the Guy called a "Vacuum Diaphragm" which he said was in the Vacuum Line between the Carburetor and the Automatic Transmission. Today I doubt it was a true Diaphragm but rather some sort of Oil Limiting/Collecting Surface.

Bruce,

Oh yes it was it was there to sense the reduced vacuum caused by the driver putting their foot down and would let the motor suck ATF if the diaphragm split.

Oddly the Ford cruise-o-matic box normally only used 2nd and top, 1st was only engaged when you flood the loud pedal.

[Nick Clarke 3Participant @nickclarke3]

While a student I moonlighted at a number of small backstreet garages, including one where the TV and electronics engineer partner (don't ask) also did trade repairs on autoboxes, often BW DG or Model 35 and 13J

His own van was converted to auto with a BW35 but it was fitted with a rear pump in addition to the normal front one which was used by the engine input to pressurise the system so if you rolled it down hill fast enough (30 – 40 mph!!) the rear pump would act in place of the front one and enable the brake bands to operate and the torque convertor would bump start the engine – sometimes! The rear pump was only used on some Triumph and Rover cars and then no for long, but all of the casings could accommodate one if you had one spare lying around.

Another memory is taking the metal plates out of a worn multiplate clutch in a BW box and being warned to take care as they were sharp. Even though not causing a problem the plates had worn down from approx 2mm thick to the point where they would cut a sheet of paper!

Perhaps not as efficient as has already been suggested, but they were incredibly engineered for a mass produced item!

PS:- The AP auto gearbox fitted to the BMC minis an 11/1300s were produced in a factory just round the corner from where I am typing this, on the Pershore Road, Stirchley in Birmingham.

Edited By Nick Clarke 3 on 07/06/2023 15:26:47

[Andy StopfordParticipant @andystopford50521]

The Borg Warner DG (used on older Jaguars) had a rear pump as well. I had a Jaguar Mk10 which needed to be rolling at 25 – 30 mph to engage the gears and allow a bump start – not a procedure for the faint-hearted since with no power assistance the brakes were basically inoperative (not that they were that great even with the engine running).

Iveco fit a thing they call an automated gearbox to some of their smaller lorries – a conventional manual gearbox and clutch, but with various servos to shift the gears and operate the clutch. I think they're absolutely horrible to drive because there's quite a lengthy pause between pressing the accelerator and the gearbox deciding its time to engage a gear and let the clutch in. This is not what you want when trying to pull out into a gap on a busy roundabout.

[duncan webster 1Participant @duncanwebster1]

CVT transmission used by Fiat and others was a development of the DAF system, the belts seemed to last well, or perhaps it was a service item. Father in law had one in a Punto, probably the only thing that didn't give trouble.

[Chris Pearson 1Participant @chrispearson1]

Posted by Nick Clarke 3 on 06/06/2023 10:10:27:

Manual gearboxes were extremely difficult to use until the introduction of synchromesh …

"Extremely" is a bit extreme.

My late father (born 1920) used to start in 2nd because he was brought up with limited synchromesh. By the time that he could afford a car, the gearbox probably had it on 3rd and 4th.

I have one car (TR2) with limited synchromesh and a couple of pre-war cars with none. They are not that difficult to drive!

[HopperParticipant @hopper]

Posted by Chris Pearson 1 on 07/06/2023 21:32:09:

Posted by Nick Clarke 3 on 06/06/2023 10:10:27:

Manual gearboxes were extremely difficult to use until the introduction of synchromesh …

"Extremely" is a bit extreme.

My late father (born 1920) used to start in 2nd because he was brought up with limited synchromesh. By the time that he could afford a car, the gearbox probably had it on 3rd and 4th.

I have one car (TR2) with limited synchromesh and a couple of pre-war cars with none. They are not that difficult to drive!

These days they would be considered "impossible" to drive. A policemen told my my car is unlikely to get stolen because the youngsters who do such things do not know how to drive a manual car.

And apparently manual cars are harder to sell secondhand for the same reason. Many youngsters here get their license in an automatic and never get the endorsement now required to drive a manual.

Changing gears? Physical effort? Isn't there an app for that?

[Nick Clarke 3Participant @nickclarke3]

Posted by Hopper on 08/06/2023 01:40:18:

A policemen told my my car is unlikely to get stolen because the youngsters who do such things do not know how to drive a manual car.

And apparently manual cars are harder to sell secondhand for the same reason. Many youngsters here get their license in an automatic and never get the endorsement now required to drive a manual.

Changing gears? Physical effort? Isn't there an app for that?

For years I recommended anyone learning to drive to learn and pass their test in a manual car because that left all their options open but nowadays it is far less important as the next new car someone drives is likely to be electric or hybrid, both of which count as automatics.

[Howard LewisParticipant @howardlewis46836]

It used to be that, in UK, to pass the PSV or HGV driving test one had to be able to bring the vehicle (With an unsynchronised – "crash" box) to rest usingbthe gears and the handbrake.

A friend had a preserved Austin K2 A T V, which had a knob rather than akey to moperate the ignition switch,

The gearbox was unsynchronised, and rather like the Bedford O lorries and OB buses and coaches made lovely "vintage" noises . The gear change was light, BUT you HAD to get nthe rvs right, or else the whole world knew about it.

He used yo leave it boutside his house, saying if anyon took it, "They probably wouldn't get past the end of the road, being unable to get into second gear".

With such a gearbox and less efficient brakes than today, it certainly taught you to look ahead and anticipate!

On the Bristol buses (LDs and FLFs )used by Brighton Hove and District, with a skilled driver, and a properly adjusted clutch stop, upward changes could be made quickewr than on a syncromesh box.

On the Southdown Bristol REs,with the manual box, the synchro on second was so poor, almost non existent, and there was none on fifth gear, so safest was to double declutch every gearchange.

A "crash" box was usually lighter and sometimes quicker than oine with balky synchromesh.

If the clutch operating system failed, (Fluid leak or broken cable ) by driving as if unsynchronised, it was possible to drive. (onbce across town in the evening rush hour, and once the 55 miles to home.

Our daughter brought her car home to Peterborouygh from the Hague when the clutch cable broke!

On vehicles with heavy clutches, such as the Scammel Pioneer, it was quite usual only to use the clutch when starting or stopping.

Howard

[John HaineParticipant @johnhaine32865]

I had a Fiat500 old model with constant mesh, at least on some of the gears. I learned to double declutch quite quickly after a while found that I was depressing the clutch less and less so decided to stop using it except when starting off as an experiment, it worked very well. But it was a horrible car, shed all the teeth on the sprocket driving the camshaft after not many miles, apparently a standard fault.

[SamsarandaParticipant @samsaranda]

During my time in the Air Force at one station I used to drive an ancient Bedford Tanker which was filled with hot de icing fluid which we used for hot de icing of large transport aircraft. The tanker was quite large and I am sure that there was no syncro in the gearbox but the worst aspect of driving it was that it did not have power steering, it was a real brute to manoeuvre round corners with god knows how many thousand gallons on board in the tank, driving it was better than a workout in the gym. Dave W

[vintage engineerParticipant @vintageengineer]

I have a 1979 Ford F100 truck with a 302cu in v8. It has an autobox as they were cheaper to produce than a manual box that would take the power of the engine.

[Robert Atkinson 2Participant @robertatkinson2]

Modern CVT 'boxes use metallic link belts not an elastomeric ones like the old DAF 33. My Outlander plug-in hybrid has one CVT 'box plus two motors and a generator. It can run pure electric on one or two motors, IC only, IC + 1 motor in parallel, IC + one or two motors in series / parallel. The software tries to keep the IC engine on a optimum operating point and changes mode automatically depending on demand and battery state of charge.

Robert.

[john halfpennyParticipant @johnhalfpenny52803]

When I was a development engineer on hydraulic auto gearboxes, the two significant problems were starting from rest, and getting a smooth gear change without flare or tying up (for all oil temperatures and throttle openings). The first was typically solved with torque converter, maybe also fitted with lock-up clutch for the last 5-7% of slip. The latter was addressed by ever more complex valve blocks, but by the early 80's we saw the early use of electronic position control for a manual type clutch, and electronic maps to account for the shift variables.

Our prototype DSG on a Ford Fiesta never reached production, but VW did make a big success of it a few years later.

I have a modern hydraulic 8 speed auto, and am very impressed with the shift quality under all conditions. It's very difficult to catch out the logic, and the packaging is very impressive.

[John Doe 2Participant @johndoe2]

It certainly is very impressive. And with electronic control, they have solved the clutch activation – my Audi DSG gearbox feels as it if had a fluid torque convertor, (without the losses), but it has two conventional friction clutches, actuated automatically by servos. They have got the logic of the clutch engagement just right, and pulling away from rest is absolutely smooth and seamless. Very clever.

All this and 7 gears + reverse in a front wheel drive gearbox housing

Edited By John Doe 2 on 09/06/2023 10:05:37

[john halfpennyParticipant @johnhalfpenny52803]

The beauty of DSG is(was) that 95% of the gearbox is identical to a manual. All that is needed is a quill shaft through the mainshaft cluster and a small wet clutch at the opposite end to the main clutch. So it fitted in the same space as a manual and coukd have the same number of ratios, but of course manuals are no longer required by most users.

DSG itself is a very old idea -used by Citroen and others more than 100 years ago. It can give a power on shift – very useful for tractors

Edited By john halfpenny on 09/06/2023 11:13:33

[SillyOldDufferModerator @sillyoldduffer]

Posted by john halfpenny on 09/06/2023 11:10:31:

… but of course manuals are no longer required by most users.

…

Though manuals are in decline, they're still the most popular single type of transmission as this graph from Statista shows:

Quite interesting to see what manual gearboxes are losing out to – it's not plain automatics, sales of which are also dropping. Winners: AMT, rare but growing slowly; with CVT and DCT both big players.

There's a mystery! The graph shows the fastest growing transmission type is 'others', predicted to have 9% of market share by 2025. I guess these could be the incoming electric transmission systems, does anyone know? Or are there other types, perhaps driving hydraulic motors on each wheel?

Dave

[not done it yetParticipant @notdoneityet]

Posted by Simon Robinson 4 on 05/06/2023 15:39:49:

In modern Automatic cars the Engine management system detects the need for a gear change through things like the MAF sensor which detects strain on the engine. But in early automatic transmission cars there were no computers or even MAF sensors etc. So how did the planetary transmission system know when the engine was under strain such as climbing a hill or moving in slow traffic etc?

In a few years time, the modern gearboxes will, I expect, all be single speed reduction, so no longer a need for electronics to control the gearbx.🙂

This is an interesting thread on bygones and those that preserve them. I just off-loaded my last automatic gear-boxed vehicle. All I remember of the 1970’s Borg Warner three speeders was that there must have been an over-ride switch (as well as smooth control for normal progress) when the ‘kick-down’ was required. The minis, with the four speed box, had an easy change from top to third, rather than the less-than-precise manual selection with the three speeders (really only required for maintaining a lower ratio, rather than anything else).

[john halfpennyParticipant @johnhalfpenny52803]

The AP (Mini) box allowed lower gears 123 to be held and changed manually, or be fully automatic in D. Regrettably never fitted to sports cars, but I did often have an Alfa 2 litre prototype with 4 speed auto transaxle at weekends. Canned by Fiat, but a fabulous machine for visiting my girlfriend, instead of my more mundane transport. My best Preston to Warwick was 1 hour 42 min on a Sunday evening in 1976.

[Howard LewisParticipant @howardlewis46836]

Back in the late 20s, the Tilling Stevens buse was a petrol electric (Similar in basic principle to the Diesel elctric locomotive ) Because of the poorer technologies then available, and being DC, then they were not immune to faults such as flashover.

Not quite like our modern Hybrids

Howard

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