Unusual ways to change gear, cont'd

"Cé hé sin" (michael-m-mouse) 02/10/2020 at 15:35 • Filed to: Rover, Roverdrive, Unusual ways to change gear

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Time to visit Auntie. Auntie? Auntie. The Rover P4, made from 1949 to 1964, a long and with hindsight too long model life as it gave Rover a staid and old fashioned image.

It tended to appeal to drivers of a similar specification and so Rover decided that they might appreciate something easier to operate than the standard and partially synchronised manual (it began with synchro on third and fourth only). They could have used one of those newly introduced automatic boxes but they came from America and attracted import duties, being foreign. Something home grown would be more affordable and so Rover came up with the Roverdrive. It was fitted for only two years to a specific model, the 105R, which had that many bhp . Yes, Rover plus overdrive, but not only overdrive .

Beginning at the front, Roverdrive consisted of a torque converter, a clutch, a two (yes, two) speed synchromesh gearbox and a Laycock overdrive unit, a thing much in vogue with the UK motor industry (and Volvo) until the 70s and 80s.

As the service sheet sets out, the driver was equipped with a gated gearchange, just like a Ferrari but with fewer possibilities, and a gear knob with a button on top. Press the button and a vacuum servo released the clutch. Just the two forward possibilities were offered and the lower of these was “emergency low” if the driver found himself (of course himself - t his was a car for chaps) starting on a steep hill. Otherwise high gear sufficed. Once high was engaged one could introduce the pedal to the floor and the car would shoot off. Relatively speaking. Even by the standards of sixty plus years ago the 105R offered performance of an extremely modest nature, with road tests producing a 0 to 60 time of about 23 seconds. Quite what it was like to drive I’ve no idea, but as overdrives usually worked better with a clutch I’d guess that the solitary gearchange was not the smoothest around.

Only about 3,500 Roverdrive equipped P4s were made but as they were qu ite durable (the steel used was thicker than the norm , which helped) there are still a few left. Want one? P robably not but should you, a decent roadworthy one will set you back about £5,000.

Jim Spanfeller > Cé hé sin 02/10/2020 at 15:53

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So... correct me if I’m wrong... but does that mean the speed of the car is basically jus t controlled by how much the torque converter slips? That sounds like a transmission GM used in the early ‘60s. It was basically just a giant torque converter with an additional reverse gear, so speed was determined by how much the transmission was slipping. I t gave you perfectly smooth acceleration, but was quite possibly the least efficient transmission design of all time. Mr. Regular reviewed a Bu ick with this transmission at some point...

RamblinRover Luxury-Yacht > Jim Spanfeller 02/10/2020 at 16:28

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https://en.wikipedia.org/wiki/Dynaflow

Insane, but still less deranged than using both a torque converter and a standard gearbox *with clutch*.

Jim Spanfeller > RamblinRover Luxury-Yacht 02/10/2020 at 16:39

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Ah, thanks for reminding me what it’s called. It was driving me crazy.

Cé hé sin > Jim Spanfeller 02/10/2020 at 17:16

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To a considerable extent, yes. There were plenty of two speed automatics around then. GM had various manifestations of a transmission which used a torque converter with two turbines, each driving a different gear. Very smooth, hideously inefficient. Honda used a manually operated two speed for quite a long time which could be kept in top gear most of the time.