Please understand that Automatic Transmission Fluid acts as a Lubricant, and a Coolant . As a Coolant, it carries heat away from the Transmission to the Heat Exchanger in the Radiator. Having said that, you can understand, in an extreme case, the level of damage that happens to the Transmission, if the engine cooling system fails, and looses all coolant, then the Transmission can also overheat. As a Lubricant, the fluid stops wear in bearings and gear faces, but it can’t act too good as to stop the Friction Clutches and Friction Bands from grabbing.
In the case of the ZF 5 Speed Transmissions, the fluid has been specifically tested to provide satisfactory performance for the life of the transmission. In the world today, testing a Transmission Fluid for Operation and Longevity would be costly, and probably prohibitive.
I went into the ZF Database for the specification of the Transmission Fluid for the ZF 5HP30, ZF 5HP24
and ZF 5HP18. In TE-ML 11 the subject of Longevity is discussed.
5 and 6-speed as well as 4HP20 automatic transmissions:
ZF 5 and 6-speed as well as the ZF 4HP20 automatic transmissions are filled maintenance-free with specially developed partially synthetic ATF oils. Maintenance-free fills are intended for normal operating conditions. Especially driving at very high operating temperatures can result in accelerated aging or increased wear of ATF oils. It is recommended, in the event of severe operating conditions, such as:
- frequent highway driving in top speed range,
- offensive, sporty driving style,
- frequent trailer operation,
being above average, oil purification (oil change) on automatic transmissions is recommended between 80,000 km and 120,000 km, or 8 years, depending on the load. In each case, only released ATF oil may be used for oil changes. And oil changes must be performed in accordance with the relevant
Specifically, these transmissions are to be serviced according to ZF TE-ML 11. In TE-ML 11 are two categories of fluid, 11A and 11B. The 11B is a more robust, longer life fluid with similar properties to 11A. Also listed under 11B is Esso LT71141, the fluid that has been recommended for the 5HP 30 transmission.
Link to TE-ML 11
Doing a Further search I found the Esso LT71141 also listed in ZF TE-ML 14. TE-ML 14 has four catagories of fluid, 14A, 14B, 14C and 14E. The 14C is a more robust, longer life fluid with similar properties to 14A or 14B. In TE-ML 14, ZF has characterized fluid by giving each rating a life in miles / years. This should only be used as a comparasin between the different fluid ratings.
Link to TE-ML 14
Having said all of this, I believe that any Dexron III will work in the transmission. The question is life. I believe that you can print the designation LT71141 on a bottle ATF in the Fast Mart without reprocussion. Now, what fluid to use?? The Esso LT71141 is rated for Service TE-ML 11,14. The Pentosin ATF1 is rated to 11B, no mention of 14. The new Mobil1 is rated ZF TE-ML 03D, 04D, 09, 14A, 14B, 16L, 17C, not bad but misses 11, 11A or 11B. Wolfshead Synthetic ATF is rated 11B, 14C.
Like I said before, Transmission Life is based on monitoring the condition of the fluid and replacing the fluid before the properties of the fluid starts to fail. Replace the Filter before it becomes restrictive. And fill the transmission with the best fluid possible.
Below are the links to the Manuals for the respective ZF Transmissions