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911 Porsche World - - Practical Porsche -

BACK­GROUND

In the mid 1960s Porsche’s de­vel­op­ment work on an auto box for VW prompted re­newed in­ter­est in a clutch­less trans­mis­sion for the 911. Ferry was against a full au­to­matic, not part of the pure sports car im­age, and in any case transaxles for au­to­mat­ics were un­de­vel­oped. Porsche’s route was a clutch­less man­ual which used a hy­draulic torque con­verter re­plac­ing the con­ven­tional fly­wheel and mated to a four speed 901 gear­box. NSU’S Ro80 had a sim­i­lar trans­mis­sion. On the 911 the torque con­verter used oil from the en­gine sup­ply and the con­verter al­lowed the mo­tor to idle with­out stalling while a clutch op­er­ated by a vac­uum servo in­ter­vened only to break the drive. As it did not have to ab­sorb the power and heat gen­er­ated by tak­ing up drive, a task un­der­taken by the torque con­verter, a spe­cial, lighter 7.5 inch clutch­plate was fit­ted. In­side there was no third pedal and the gear­lever ac­ti­vated a switch which dis­en­gaged the clutch en­abling shift­ing with­out en­gage­ment of the driver’s left foot. The mul­ti­pli­ca­tion ef­fect of the torque con­verter ef­fec­tively length­ened the ‘range’ of each gear, so four for­ward speeds more than suf­ficed.

The Sportomatic was greeted scep­ti­cally by the US auto press, but the Euro­peans were im­pressed, gen­er­ally find­ing that speed of gearshift­ing al­most made up for torque con­verter losses in ac­cel­er­a­tion. Porsche would sell more Spor­tos in Europe than it pre­dicted and the Sportomatic re­mained an op­tion to the end of the 3.0 Car­rera in 1977, by which time it had been re­worked as a three-speed for the greater torque of the big­ger en­gine. Ac­cord­ing to some ac­counts, Sportomatic trans­mis­sion could still be or­dered un­til 1980. WHERE Phil Raby Porsche IS IT? is at South­bourne, off the A27 be­tween philraby.co.uk Portsmouth 01243 and 780389 Chichester. FOR Very rare model, com­pre­hen­sive re­build, em­i­nently us­able AGAINST An ex­pen­sive cu­rios­ity; may not suit all tastes VER­DICT For the se­ri­ous col­lec­tor, a su­pe­rior Sportomatic might take years to find. En­joy this one now!

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