Regarding the transmission fluid used in the pre-’04 4.4i and 4.6is E53 5-speed transmissions - in terms of viscometrics, density, chemical compatibility, air solubility/anti-foaming, shear resistance, flash point, etc., etc., other ATFs may deliver a similar spec. to Esso/Mobil LT71141 but this entirely misses the most important point.



The 5HP24 is fitted with a controlled slip converter i.e. the torque converter lock-up clutch isn’t only switched ‘on’ or ‘off’ but is also controlled to slip at speeds of up to 50rpm (around 1kW power dissipation). This enabled ZF to dispense with the traditional LUC torsional vibration damper in the torque converter to save weight and space.

The friction characteristics of this clutch were optimised specifically around LT71141. It is essential that the static-to-dynamic friction characteristic & the dynamic coefficient of friction increases as slip speed increases to prevent control oscillation and these friction characteristics must fit within the relatively tight band shown in the graph below.




If you use any other fluid there’s a strong possibly that it doesn’t contain identical friction modifiers and you run a high risk of burning out the converter lock-up clutch, harsh LUC shifts and oxidising the oil (leaving the transmission vulnerable to other problems too).

It’s expensive stuff but, if you wanted to shop around, the following are all genuine Mobil LT71141 fluid :

ZF Lifeguardfluid5 (ZF Part No. S671 090 170)
Audi / VW - Part No. G 052162 A1 / A2 / A6
BMW - Part No. 8322 9407807
Citroen - Part No. Z 000169756
Jaguar - Part No. JLM 20238
Land Rover - Part No. STC4863
Mercedes Benz - Part No. A 0019892203
Peugeot - Part No. Z 000169756
Porsche - Part No. 999.917.547.00


Phil