From the tech manual:
Hydraulic System Bleed Procedure -- Reason: To remove air trapped in the hydraulic system which will prevent proper operation. (Special or Essential Tools: • BW13586 Ballast Box)
Procedure: NOTE: Fill the new hydraulic oil filter with new oil before installing.
1. Install a new hydraulic oil filter.
2. Fill the transaxle with specified JDM J20D (preferred) or J20C oil to the proper level on dipstick.
3. Disconnect plug (A) to fuel shutoff solenoid. M91946
4. Turn the key to START and hold for 10 seconds. Turn the key to OFF.
5. Reconnect wires to fuel shutoff solenoid.
6. Raise machine front end and support on suitable stands.
7. Start the engine and run at low idle.
8. Slowly turn the steering wheel left and right until wheels turn smoothly indicating that any trapped air has been bled back to the reservoir.
9. Operate rockshaft several times until it operates smoothly.
10.Stop the engine and check the hydraulic reservoir oil level. Fill as needed. Check all line connections for leaks; tighten if necessary.
11.Lower the machine to the ground.
12.(eHydro machines) Drive machine in forward and reverse several times until transmission operates smoothly.
Here's a link to another thread where someone thought they had trapped air problems...
Front End Loader Question