After you've checked the wear in the working piston you can continue taking the rest of the steering box to bits.
Get a 65mm open ended spanner to remove the lock nut on the cap that covers the input shaft (or the equivalent tool for your steering box). It might be necessary to hold the inner part of the cap with a pin spanner.
Here's a picture of the input shaft and cap in bits
Remove and replace the rubber and plastic seals in the cap.
Place the working piston and worm gear in a plastic bag and unscrew the steering worm so that the ball bearings fall out. There should be 24 balls. (PHOTO)
You can then unbend the tabs on the working piston to gain access to the screws that hold the detachable bearing races in place.
