Background
Your average Joe might look at an XJ40 and see a car very similar to the Series III XJ6 that it replaced. And that was partly the idea, with continuity of styling and brand history at the forefront of Jaguars’ designers’ minds back during its ludicrously long inception, but in reality it was a completely new car with very little carry-over of either body or mechanical components.
At the time the XJ40 was the most complex Jaguar ever built. Chief Vehicle Engineer, Bob Knight, and Technical Director Jim Randle headed the project – two brilliant and tenacious individuals that many claim Jaguar itself owes its very existence to.
Their work pioneered significant improvements as to how future Jaguars were designed, built, and assembled. The design brief for the XJ40 included a need to reduce manufacturing complexities to improve productivity and quality. Reliability had to be improved, and it was also important that the new model had improved fuel economy – gains that were engineered by reducing weight, improving aerodynamics, and the use of more advanced engine management systems.
Most importantly, the new model had to achieve better performance than its predecessor and maintain the big Jag’s position in the luxury sector by at least equalling the out-going model in style and refinement.
Compared with the Series III XJ6, the XJ40 had 136 fewer body pressings – a 25% reduction in the number of panels required per car. An example of this was the inner door panel which was made from one instead of three parts. Overall, this resulted in not only a more efficient assembly process, but also a weight saving and a stiffer overall structure. Randle was attempting something genuinely new – creating a lightweight Jaguar.
The new car was powered by a new engine too – out went the back-breakingly heavy iron-blocked 4.2-litre XK unti, and in came the all alloy AJ6, in SOHC 2.9 and DOHC 3.6 litre varieties. Both offered massive weight savings and performance efficiencies over the old unit, whose origins went back to World War 2.
Amazingly, the AJ6 is only the third new engine ever designed by Jaguar. The new engines were revised in 1990, with the 2.9 becoming the double overhead cam 3.2, while the 3.6 became a 4-litre powerplant, still with two upstairs camshafts.
The new XJ40 was launched in 1986 and widely applauded. It gave way to the heavily revised X300 model in 1994, followed by the X308 version in 1997. The XJ40 and its later derivatives is the second longest running Jaguar XJ platform, with a total production run of 17 years. Because the model that superseded it was produced under Ford’s ownership of Jaguar, some enthusiasts refer to the XJ40 as the last real Jaguar, although to be fair the new American owners did a lot to improve build quality.







