Looking for a good ATF to use in my 86 truck with the A43D transmission, originally listed for Dex II. I see there are some concerns with the viton rubber seals in older transmissions and Dex VI. I am looking at Valvoline Maxlife and Mobil Delvac. Anyone using one of these in an older Toyota transmission.

 

I only use dexron VI on mine, (220,000) miles.

 

why the heck are you guys switching to a synthetic fluid in an aged automatic? there are so many things that can go wrong with that. yes, it is a better fluid, but it's properties are different and can effect valve pressures and not to mention, incompatability with conventional atf can dry out and kill the seals before they take the new fluid. aside from that, the clutches do the same. it leads to tar/sludge in whom knows where. if you are going to make the switch from conventional to synthetic, it's best done when the trans is rebuilt. there is hardly any difference in brands of atf, just cheap and better. biggest thing is keep it clean.

 

Owners manual says to use Dexron II ATF wich is not available anymore, so dexron IV is just an updated new version of the original dexron from the 80's but is just conventional ATF not synthetic ATF, and my transmission is running like a champ.

 

dextron IV is fine, but you said dextron VI which is synthetic

 

I've heard some say if you are converting over to a synthetic, do a gradual conversion. Also heard the Maxlife isn't a true synthetic, but a highly refined conventional ATF.

 

Use what is factory comaptible & I would also add some Lucas ATF treatment. It is like there oil treatment a little thick & very red. Hope that helps you. As always take the advice of others with a grain of salt. Some bad, some good. Just use your own judgement of it.