Best substitute for ATF HT389

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Nov 20, 2022
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Hi
I am the latest owner of a 1984 Tucker SnoCat. The power steering/groomer pump is somewhat low on fluid. I called Tucker, they recommend Chevron ATF HT389 for the 1984 and still use it on new deliveries(?). It is not readily available in small quantities. The best substitute I could find is Valvoline DEX/MERC ATF. Best of all it is pretty cheap. There will be a complete flush and fluid change in the spring.
Valvoline says it is a recommend substitution for DexronIII, Mercon, Allison TES-389, Allison C-4 and a couple of others (Ford and Cat). These fluids would have been current for an 1984 hydraulic system requiring ATF. The Chevron spec for HT389 says it is compatible with TES-389 Schedule One so I am thinking they should be very similar. I understand the early Allison's had seal problems with some of the more current fluids. The hydraulic system is original. The pump was made by Vickers, the steering valve was made by Gresen and hydraulic cylinder was made be Garrison if that helps.
Questions:
Is this a good substitute?
Is there a better one that is available in 1gal quantities?

Thanks, I hope I didn't get too long winded.
John
 

John4401

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Nov 20, 2022
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I did not see that Maxlife Multivehicle ATF was also compatible with TES-389. The only difference I could find between the Maxlife Multivehicle ATF and the Dex/Merc ATF was the Maxlife Multivehicle was synthetic based and had seal conditioners. Also much more expensive.
 
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I did not see that Maxlife ATF was also compatible with TES-389. The only difference I could find between the Maxlife ATF and the Dex/Merc ATF was the Maxlife was synthetic based.
Maxlife is Dex VI/Merc LV type fluid and the Dex/Merc is a full viscosity fluid, also the Dex/Merc is more compatible with some older Allison transmissions, I think they had problems with excessive seal hardening with Dex VI in transmission made prior to 2006 and made some changes to the elastomers used in newer transmissions.
 

John4401

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Ok, I think I will go with the Dex/Merc. Cheaper and it might not harden the seals the pre-2066 seals. That may be why Tucker still recommends and uses the HT389.
I doubt there is much real difference between the two.
 
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