A little more information may help us give you a far better guess as to what you are asking.
model? serial? make?
when does it bounce? driving empty and not touching the controls? while lifting? when you stop lifting? loaded or unloaded? in reverse? only when changing directions?
how high does it bounce? does it have a bleeder on the lift cylinder? does it have fingertip controllers or levers and linkage to the control valve. does it have a hydraulic accumulator?
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