Just found this.........
I have never seen one of these tools and never been able to find one to buy so, like most people, I have been forced to make one. You will need some masking tape, a hub box spanner (the one you use for removing hub bearings) and an angle grinder. Spray paint can and metal file will be useful for smartening it all up.
Bearing Adjustment Nut Spanner Rover Differential
Making Your Own Spanner-differential
To make my own Bearing Adjusting Nut Tool I have modified my hub box spanner to be duel use. One end is still a normal hub box spanner used for replacing wheel bearings but the other has been modified to fit the bearing adjustment nut.
Bearing Adjustment Nut Spanner Rover Differential
First, we put some masking tape around the round end of the hub box spanner so we can make clear pencil markings and put this end up against the bearing adjustment nut on one side of the differential (you may choose to remove it if you can to make this easier). Mark out three equally spaced gaps from the bearing adjustment nut and shade out the remaining space for cutting and removal.
Bearing Adjustment Nut Spanner Rover Differential
Cut using and angle grinder (or Dremel tool if you have lots of time) to leave behind only the three pegs you marked. Shape the pegs to make them more pointy to get a better fit. Test the tool and shave any excess material.
Smooth with a metal file and sandpaper to get a smooth finish and paint with a rattle can for a professional look. It will then be ready for reducing the backlash in your differential.
Bearing Adjustment Nut Spanner Rover Differential
The hole through the hub box spanner can be used along with a sliding T Bar to torque to the correct values.