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Semi-automatic gearbox

rover 75
on 19 December 2009

I have decided to purchase a classic car ; After some deliberation my prefered choice is a Rover P2 6 cylinder in the 1939-1947 era , I also have an interest in Daimler/Lanchester from the immediate pre-war period . I like the latter for the Wilson pre-select gearbox and Daimler fluid flywheel offering a very smooth drive .
The question is why did this type of transmission fall out of favour ? It seems there are lots of current drivers who do not get on with the modern semi-automatics for example recent debates on the Honda Jazz . This might be a post for the more mature driver!
John.

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Lud on 19 December 2009

Armstrong-Siddeleys had the Wilson box too.

I don't know why it went out of favour. Expensive to make perhaps? I wasn't aware of any maintenance problems, but there may have been some.

It was indeed smooth. If the brakes failed you could put the car in reverse and rev the engine to slow it down, or so owners claimed. It made a nice noise too, a pleasant whine. Gearchanges were quite deliberate, and perhaps some owners thought it not very sporting. Would have made cars a bit thirsty too.

Most of all though, ordinary US-style slushpump autos were being made in large numbers and could easily be bought in by manufacturers. Being a minority thing the pre-selector probably just got a bit expensive.

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galileo on 19 December 2009

In the 1950's the local corporation had a number of Daimler buses, both single and double deck, which had Wilson pre-selector gearboxes and survived into the 1960's.
The early Atlantean type buses may also have had some sort of pre-selector as the gear change was a finger size lever and was moved well before any ratio change.

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Avant on 20 December 2009

The London RT buses (pre-Routemaster) had preselector gearboxes (were they the same thing as Atlantean? - forgive my ignorance!)

Daimlers and Lanchesters had them until well into the 1950s: I remember the ferocious Mrs Scott who ran Meals on Wheels in Farnham through the 1960s and 1970s, until she was over 90 - she drove a huge old 1950s Lanchester and was never going to learn to use any other form of gearbox.

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DP on 20 December 2009

The early Atlantean type buses may also have had some sort of pre-selector as the

gear change was a finger size lever and was moved well before any ratio change.

Many post-war British buses had the Leyland Pneumocyclic gearbox, which was a semi automatic "clutchless manual". Gear selection was by means of a tiny lever through an open gate, the operation of which directed compressed air to cylinders in the transmission which operated the brake bands on individual gear sets. There was a short delay between moving the lever and the change of ratio.

It was reliable, easy to operate (the "gear lever" was little more than an air valve selector) and very widely used. There are many buses with this gearbox still running today. There were also "automated" versions where the air selection was automated and the box changed gears by itself, giving the driver an option to "hold" a selected gear for hills etc.

My dad drove buses when I was a kid, and I was always fascinated by the concept of a manual shifter with no clutch pedal! :-)

Edited by DP on 20/12/2009 at 13:24

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DP on 20 December 2009

Good example here:

www.youtube.com/watch?v=GmkGX8IJDf4

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