The intended replacement for the Series XJ was code-named XJ40, and development on the all-new car began in the early 1970s (with small scale models being built as early as 1972.) The project suffered a number of delays due to problems at parent company British Leyland and events such as the 1973 oil crisis. The XJ40 was finally introduced in 1986 at the British International Motor Show.
With the XJ40, Jaguar began to place more emphasis on build quality as well as simplification of the XJ’s build process. With 25 per cent fewer body panel pressings required versus the Series XJ, the new process also saved weight, increased the stiffness of the chassis, and reduced cabin noise.
The new platform came with significantly different styling, which was more squared-off and angular than the outgoing Series III. Individual round headlamps were replaced with rectangular units on the higher-specification cars, and all models came with only a single, wide-sweeping windshield wiper. The interior received several modernizations such as the switch to a digital instrument cluster (although this was eventually discontinued for MY 1990 in favor of analogue instruments.)
The six-cylinder XJ40s are powered by the AJ6 inline-six engine, which replaced the XK6 unit used in earlier XJs. The new unit featured a four-valve, twin overhead cam design. In 1993, one year before XJ40 production ended, the V12-powered XJ12 and Daimler Double Six models were reintroduced.
The X300, introduced in 1994, was stylistically intended to evoke the image of the more curvaceous Series XJ. The front of the car was redesigned significantly to return to four individual round headlamps that provided definition to the sculptured hood. Mechanically, it was similar to the XJ40 that it replaced.
Six-cylinder X300s are powered by the AJ16 inline-six engine, which is a further enhancement of the AJ6 engine that uses an electronic distributorless ignition system. The V12 remained available until the end of the X300 production in 1997 (although it ended one year earlier in the United States market due to problems meeting OBD-II-related emissions requirements.)
Jaguar first introduced the supercharged XJR in X300 production; the first supercharged road car manufactured by the company.
Design of the X300 was directly affected by the Ford Motor Company’s ownership of Jaguar (between 1990 and 2007). According to Automotive News, this was evident in general “product development processes”, more than the use of Ford components. However, the X300’s traction control system was obtained from the Ford Mondeo and it also featured a Nippondenso air conditioner purchased through Ford channels.
X308 (XJ8) (1997-2003)
With the introduction of the X308 generation in 1997 came a switch from the XJ6 and XJ12 nomenclature to XJ8, reflecting the fact that the X308 cars were powered by a new V8 engine.
The exterior styling of the X308 was similar to the X300 with minor refinements such as a change to oval indicator lenses and amber style round fog lights. The interior was also updated to eliminate the instrument binnacle used on the X300; instead, three large gauges were set into recesses in the walnut-faced dashboard in front of the driver.
The major mechanical change was the replacement of both the inline-six and V12 engines with new eight-cylinder AJ-V8 in either 3.2 L or 4.0 L versions, with the 4.0 L also available in supercharged form in the XJR (A sport oriented model). No manual transmission was available, and all X308 models were supplied with a five-speed automatic gearbox.