FWIW, as a technician on all kinds of aerial lift machines, which use hydraulics to perform most any function, I have seen the engineers spec ATF (Dexron) as well as regular spec hydraulic fluid in their machines. Having worked on them for years I wouldn't be worried that the Dexron would have any adverse effects on any hydraulic system. The friction modifiers won't affect seals or pumps adversely and more than half of transmissions function is hydraulic applications anyway, Dexron will work well as a strictly hydraulic system fluid.
The same applies for using AFF in manual transmissions, yes there are additives that need not be present, but the fluid will perform equally as well in either application. One thing I have noticed is that Dexron usually does not perform as well in extreme cold situations as straight hydraulic fluid, depending upon the spec of the hydraulic fluid. I once was having trouble with a JLG lift performing in near zero temperatures, and when talking with a factory rep was told to just thin it at about 10% with diesel fuel or kerosene. I did that and it worked just fine for cold use. Dexron seems to require a little bit more warmup time to function in near zero temperatures. I wouldn't think that you'll be raising or lowering your top though in these conditions...……….
