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The Jensen FF: Chrysler-Powered Four Wheel Drive British Luxury Cars

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Allan and Richard Jensen created Jensen Motors before World War II. The famed Jensen FF (praised most recently by Arnold Rimmer in Red Dwarf: Return to Earth) used a sophisticated four wheel drive system and antilock brakes.

Introduced in 1965 as a 1966 model, the FF was one of the most technically sophisticated cars of its era, boasting not only the revolutionary torque-split four wheel drive system, but four-wheel disc brakes (still a rarity at the time) and highly unusual antilock brakes - acting on all four wheels. It was the first use of four wheel drive in a passenger car, and the first use of any antilock brake system in a car, the second coming years later with the 1971 Imperial. (Mercedes claimed its S-class to be the first production car with antilock brakes, but it did not come until the late 1970s).

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The Jensen FF's most unique feature was engineered by the Harry Ferguson Research Organization (the FF stands for Ferguson Formula), a company created by tractor-maker Harry Ferguson. HFRO was headed by a former racing driver, with engineering headed by a former Aston Martin chassis designer; Harry Ferguson had died in 1960, but his team continued development of a four wheel drive system for cars. Their design used a limited slip differential to allocate torque to the front and rear wheels; it had been tested using various racing cars.

The Jensen FF was largely based on the 383-powered C-V8; the four wheel drive system had the traditional transfer case behind the transmission, a propellor shaft driving the front wheels, and a conventional driveshaft for the rear wheels. The Ferguson design replaced the usual solid coupling of front and rear axles with a spin-limiting differential that allowed the front and rear tires to have somewhat different speeds, eliminating scrub and inefficiency, while still providing the benefits of four wheel traction. The method was using two secondary gears, one with a slightly higher and one with a slightly lower ratio, each with a one-way clutch, to take up the load when needed, driving the axles at slightly different speeds from each other. A beneficial side effect was adding even engine braking.

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As set up by Jensen, the car put just 37% of its power into the front wheels, providing owners of rear wheel drive cars with a familiar feel; once a wheel started spinning, the system moved extra power to the other axle. Jensen claimed that "in no circumstances can one wheel individually, or the front or rear pairs of wheels separately, spin under drive or lock during braking."

The car used a front/long arm front suspension with two coils per wheel; the front suspension, power rack and pinion steering, and final drive unit were all mounted to a removable sub-frame, bolted to the main chassis. The rear suspension was identical to the Jensen C-V8, a rigid axle with dual-rate half-elliptic leaf springs and a track bar (Panhard rod) going from the left side of the chassis to the right end of the rear axle. A four-position switch in the cabin adjusted the settings for the Amrstrong rear shocks.

The FF had some engine placement and front suspension changes to accommodate its Maxaret antilock brakes, a very early design based on aeronautical systems. The antilock brakes were praised by testers, who found they provided control while slowing the car well. The system covered all four wheels, with big 11.25 inch discs and 498 square inches of swept area; the wheels themselves were 15 inches by 6.7 inches, a fairly modest size. The tandem master cylinder allowed for hydraulic failure in one line or the other; and in any case a mechanical parking brake worked with separate pads on the rear discs.

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The interior was done in luxury; front seat passengers were enveloped in splendor with leather-covered bucket seats with shoulder belts, real wood trim, and wool carpeting; instruments included a tachometer, oil pressure gauge, and ammeter. The rear seats were rather tight, since the Interceptor was five inches shorter than a Camaro (making it big for Europe and small for the U.S., with a length of 188 inches); but the rear hatch had substantial luggage space. Jensen sold pre-fabricated body sections to repair cars that were in collisions.

The standard 383 V8 used a single Carter four-barrel carburetor producing 330 hp, with a 3.07:1 axle gearing (2.93 and 3.54 gearing could be fitted). Other, later engines included the 440 and 360; the 426 Hemi was experimented with, but the cost of the engine and suspension upgrades were prohibitive. There was even at least one Interceptor FF SP, Dave Horton's convertible, made after Jensen closed its doors; more might have been made at the factory but these 440 Six Pack versions would be extremely rare if they were made at all.

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In 1966, the Jensen FF started at £4,343 (around $12,000), plus £906 VAT, in the UK; the standard C-V8 ran around $9,750, in comparison. The weight was a reasonable 3,700 pounds.

For more, see 1966-1991 Jensen Interceptor: Unappreciated Overachiever", by Graham Robson, Collectible Automobile Volume 8 Number 3 (October 1991), and the Jensen-Healey Preservation Society web site. Much of the information in this site, and the Jensen brochure that starts the page, comes from the files of the National Automotive History Collection of the Detroit Public Libraries.

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