If the brake pedal still feel fine & brakes are pulling you up, & if the transaxle oil has not been changed for a long time - the brake chatter will be caused by the oil "going off".
Use CNH Hy Trans - you will need 50lt.
You will need to also add 3 bottles of CNH axle additive (402982A2)
Please replace the filter also - the screw on one laying horizontally on the engine bell housing (CNH
1346028C1 / Donaldson P164384)
While the oil is out of the transaxle, it is a good idea to inspect the suction screen.