Are the brake wires individual wires or are they a two conductor jacketed cable?
If individual, you should replace with the two conductor brake cable.
Single conductor wires could have small nicks which would allow moisture to enter and effect quality of braking power.
I would not drill holes in tubular axles. However look at each end for factory drain holes. Make sure, if equipped they are open and clear of debris.
Bud
USAF Retired
Pace Arrow
2003 Chev Ice Road Tracker