Hello Ryan,
Bump steer refers to the feedback due to the change in the suspension, either by up/down travel of the springs or by any other means of front axle movement. The reason the stock live axle (79-85) suspension develops oversteer is because of the very short drag link (aka. horseshoe arm). Our HySteer system relocates the turning arm to the passengers side as apposed to the drivers side with the stock setup. This greatly changes the length of the drag link rod to at least 5 times longer than the stock rod. Therefore, less feedback is received to the pitman arm by the change in axle placement (height, compression, extension, etc). So as your suspension compresses or rises depending on the road surface, minimal feedback is returned through our long drag link, which eliminates almost all of the bump steer.
Now what you are talking about is you truck wandering under braking. I am very sure that this is not bump steer related. Does your truck have an "always-on" locker, like a Detroit or an Easy Locker? or even a Spool in the front? (!!) If so then this would cause the vehicle to track unevenly as the difference in brake ability between the two front wheels triggers the locker, and since the drivers side uses a shorter axle, usually more braking power is conserved at the drivers front wheel, and hence the vehicle tends to "brake left". If this is your case, then you either have to learn to get used to it, or you will need to either remove the locker or replace it with a switchable unit, such as a Toyota Electric Locker or an ARB Air Locker.
Another thing could be a inner axle seal or felt seal. Is one of your front knuckles leaking on one side? Check the inside sidewall of your front tires. If one tire is really wet and has grease or oil leaking onto it, then chances are your inner axle seal is allowing differential oil to leak past and soak out the felt seals. Eventually the oil will leak out the rear of the knuckle and dribble all over your tire, wheel, rotor, and brake pads. We had a truck that came in for this very reason, and when test driving, it pulled TERRIBLY to the right under braking. I mean I had to turn the wheel to the left almost 1/2 turn! and then back to the right when I let off the brakes. This was a very dangerous situation and it was all caused by a brake pad that was completely soaked with differential oil.
So please check those two things and reply back.
If it is caused from bump steer, then you must be He-Man or something. You would have to over come the vehicles moment of Inertia as it tried to move the vehicles center of gravity over the front suspension compression your springs under very hard braking, and then if you were somehow able to hold on to the steering wheel 100% without it moving, then you could conceivably displace both tires by providing feedback back to the tires and having the tires deal with the bump steer rather than you at the steering wheel. But Im sure the steering column would flex or the shaft tweak before this would happen.. But its still possible, especially if your name starts with 'Big'.
-BigMike
