The only problem is that my fluid looks bright pink. If I were to drain and refill with Dex III or Dex VI I wouldn't be able to tell how many times I would need to drain and fill to completely fill it with Dex/Merc. When I changed the trans fluid on my previous XJ, I just drained and filled until the fluid was pink instead of dirty. I think it took about 4 times. I'd also feel better off leaving the ATF+4 in there instead of draining some and mixing it with Dex/Merc while I try and switch out the fluid.
Apparently, the issue is that the friction modifiers in the +3/+4 are different from the FMs in the Dexron - can anyone confirm?
As far as a fluid change, it's mathematics.
ASSUME: The AW4 has an eight-quart full capacity, and a four-quart "service fill" capacity (the drain/fill job takes four quarts of fluid.)
1st CHANGE - Four quarts are drained and refilled using D-VI. You now have four quarts of D-VI and four of +4.
Drive 3,000-5,000 miles.
2d CHANGE - Four quarts are drained & filled again. You (theoretically) have two quarts of +4 and six of D-VI.
Drive 3,000-5,000 miles.
3d CHANGE - Theoretically, you now have one quart of +4 and seven of D-VI.
Zeno's Paradox sez you won't get it all out. Practically, you won't have to! As the concentration of the FM package in the +4 decreases and the FM package in the D-VI increases, the +4 will become less of a factor anyhow Even if you "power-changed" the fluid (ran it out into a bucket from the cooler line and topped off using the other port,) you're still not going to get rid of it "all" - but you don't have to, for the reason given.
In practise, the mathematical predictions won't be followed exactly - but the results will be close enough for practical effect, so you'll be fine. I'd suggest doing at least two changes, and run a can of Berryman's B-12 in during run cycle between 1st change and 2d change, to help flush things out (which probably wants doing anyhow.)
Fluid colour isn't a reliable indicator of concentration - since D-II/IIE/III/VI, Type F, +3/+4, and MerconV are all red anyhow. You just have to have faith in the mathematical theory as presented...