Join Date: Jun 2016
Location: Orange County, CA
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
If Gillig can't tell you, try looking up what the maker of the hydraulic pump and the fan motor recommend. This means you'll probably need to get down and dirty with a flashlight and some rags to find any name plates on those two things. If your PS box shares hydraulic fluid with the fan motor, like my bus does, the PS probably will dictate what fluid is needed. Sometimes it's multiweight engine oil (Shepherd steering often used that), sometimes Dexron like my Ross TS65 needs, and sometimes it's something else altogether.
For the Voith, good luck! Voith does have a US presence, so maybe a call to them will be the best way. Whatever you do, do NOT guess or assume - using the wrong fluid is VERY BAD.