FEL operation kills engine

While working with my new (24hrs) Jinma 284 the engine kept quiting when I engaged the FEL. I have noticed a few small drip leaks but address them. I ran to the store and got AW 46 hydo fluid (O'reilly's brand) and put a gallon in. Operated better but how in the world did I loose a gallon+? I checked the Transmission fill dipstip next to the stick shift and it only had oil 1/2 inch up the stick. looking at the manual it stated “

The Transmission Box and Transfer Case are interconnected and are filled and drained as one system. Use a good quality standard hydraulic fluid or tractor hydraulic fluid as cited above for the Hydraulic System.” Many post on this site say not to use hydo fluid but rather 80w-90w. Unfortunately I did use Hydro fluid was this a mistake? I plan on doing the hydro prefilter clean today and based on the answers to the post drain the transmission box.  Any suggestions would be helpful, I signed up for membership to the site today