GM’s Turbo Hydra-matic transmissions used to be named according to the cubic capacity of the engine that they were designed to be mated with e.g. THM350 = 350 cubic inch engine. In the early ‘90s they changed their naming system to be ‘more descriptive’ so that the THM400, for example, became the 3L80 where the ‘3’ refers to the number of gears, ‘L’ means Longitudinal (‘T’ for Transverse) and the ‘80’ is the “relative torque rating”. The 5L40-E is therefore a five speed, longitudinal transmission with a torque capacity below the 4L60 or 3L80 but higher than the 3L30. The final ‘E’ just means electronic control. No particular clues to the actual torque capacity there then.
However, BMW call the 5L40-E transmission (which incidentally was built in Stevefmr’s hometown of Strasbourg) the A5S360R which, according to BMW’s naming system, means it has a torque capacity of 360Nm. (They call the early petrol L322 ZF 5HP24 gearbox the A5S440Z to reflect its 440Nm torque capacity).
The TD6 engine produces
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Not sure what the final drive ratio has to do with anything but for L322 the TD6 models have an axle ratio of 4.10 whereas for the petrol models it’s 3.73.
Phil