Are you saying that the coupler is loose on the steering box input shaft or that the steering box has play in it before the wheels start moving?

Are you checking this with the engine running or with the engine off? If the engine is off, the steering box will have some free-play in it. You can move the steering wheel left to right and the box input shaft will move some without the wheels moving. Once you start the engine, the free-play is removed and the wheels should start turning as soon as you turn the steering wheel.