if it only pulls...........
when you are braking, it is probably a brake problem, like a sticking caliper or a hose that has collapsed internally.
as far as fluid still being black, flush it some more, but it is not causing your pull
try swapping sides with the tires and see if the pull goes the other way, if it does you have a bad tire
2009 Harley-Davidson Road Glide
1996 F350 CCLB 7.3 5 speed 4x4