What kind of fluid should be used now for 727 and 904 from the 60's and 70's?
I don't think you intended to say this IC, but that statement could be read as you can use any transmission fluid you choose and it won't actually harm the transmission life....My neighbor had his 41TE rebuilt by an independent shop that used Royal Purple. They told him that adding any other fluid than the Royal Purple would void his warranty with them. It made it difficult for me to suggest to him that ATF+4 (MS-9602) is the preferred fluid.
I don't think that any particular ATF would actually harm the transmission life and ATF+4 would be a good choice.
ATF+2 and ATF+3 has superseded to ATF+4. More info here:
Chrysler transmission fluids: 7176, ATF+3, ATF+4
I don't think you intended to say this IC, but that statement could be read as you can use any transmission fluid you choose and it won't actually harm the transmission life.
Using the recommended ATF or an equivalent of equal or better quality and the right properties, won't harm the transmission life.
From best I can tell, the only ATF's more durable and higher quality than ATF+4 are the exotics, like Royal Purple, Redline, AMSOIL and maybe Mobil1 Synthetic ATF.
So, if you have a late model transmission that specifically states to use only ATF+4, we all know what happens when you use DexronII, Mercon or TypeF. But anecdotally, I've read accounts of folks using Royal Purple, Redline, AMSOIL and Mobil1 Synthetic ATF and reporting the trans worked fine and did NOT shorten the trans life.
In this case a TorquFlight 727 and 904, that DexronII was originally recommended for and Chrysler/FCA now recommends to retrofit to ATF+4 if changing the fluid, you're going to a more durable, higher quality fluid, the only argument is if you're wasting money with overkill on better than needed ATF. Or you can use the even better exotics I spoke about.
I'm guessing you agree.
There was an article about using Dexron6 in the 727/904's that originally recommended DexronII. It was discussed on the forum. I think most agreed with the article, that a 727/904 that originally DexronII was recommended, you could switch to ATF+4 or Dexron6, both would be a better fluid. A few disagreed and worried the Dex6 has some different properties and lower viscosity than the orginal recommended fluid and suspect it might NOT protect as well. But then again, ATF+4 has many different properties than the original DexronII.