General Motors 5L40-E / 5L50

General Motors' longitudinal five-speed — and a good example of a gearbox reaching far outside the company that made it. It is in the Cadillac CTS, SRX and XLR, the Pontiac G8 and Solstice, the Saturn Sky and the Holden Commodore, Ute and Caprice; and also in the BMW Z3 and, behind the TD6 diesel, the Land Rover Range Rover L322.

So a BMW or a Range Rover owner researching "my automatic" is researching a General Motors transmission, which nothing on the car tells them and which changes what advice applies.

Its characteristic failure is a slip or flare on the 2–3 change, from the clutch pack that serves it, and like most such faults it begins intermittently and warm. The pressure control solenoid and the input and output speed sensors are the other three recurring items, and all three produce a limp mode that reads as catastrophic and is not.

The fluid is the part people get wrong, because these were sold as sealed-for-life. They are not, and a unit still on its original fill after 150,000 km is the commonest version of every complaint above.

The 5L50 is the strengthened later version, not a different gearbox — but its internals differ enough that a parts list for one does not serve the other, and the tell is the model year rather than anything visible on the case.