Welcome to TBN Phil :thumbsup:
On my 4WD L3010DT - read gear transmission vs Hydro, the same oil is used in the front axle. I think the same is true for the Hydro units.
Warm it up a little. There are several drain plugs under the transmission. I start with the highest one with a five gallon bucket under it. When you drain that one it will nearly fill the bucket. Then go around to the lower ones and drain them. You won't get nearly as much from them. Replace the filter. Fill it back up through the caped opening in the top rear above the 3ph lift arms. You might find it hard filling from a 5 gallon pail of oil. I always buy at least one 2 or 2 1/2 gallon container of oil and fill using that. I just keep pouring the 5 gallon pails into the small one. It will take about 10.5 gallons.
On the front axle there is a lower drain plug on each side just inside the wheel. On the cross axle itself there are two plugs facing front. Fill thru the right plug (highest) until oil comes out the left plug. Check it after a little use or a couple days and refill because it takes a while to get the air out sometimes.
You should get an Owners/Operators Manual (not service manual). It describes all the maintenance items very clearly. I believe Messick's on line has them if a dealer doesn't.
Good Luck
