Lift the cab, on the right side where the steering levers link to the arms on the pump. They have 2 round pucks on each arm that wear, the stops they touch also wear. You can get it working without replacing them but you are best replacing th pucks and flipping the stops if they are not worn on the other face.
Block the loader so the wheels are free to spin.
Remove the linkages to the levers at the pump.
Loosen the front and rear stop bar, 2 bolts each. Start the engine and holding the lever and stop stop together twist it till the right hand wheels stop moving. You really only need to twist the top as the lower bolt has just a round hole but the top is slotted for adjustment. With the bolts tight, push the arm forward and back then let it spring back to center. If it still creeps, repeat the procedure. When its set, do the front one the same way. They can be a little touchy but you will get there.
Good luck!