Pulling to the Left and Right??

When I drive my 89 Classic, it drives pretty straight on its own. However, when I brake, the car pulls to the right, so I figured that the caliper. However once the car gets to operating temp, it starts pulling to both the left and right sides. I cant figure out why though. I have been driving the truck for about two years now, and didnt have this problem until recently, when my swivels started leaking. I fixed the leaking, cleaned off both brake dics and pads. Any suggestions as to what it is? Thanks.

KelseyM.
89 RRC

if you dissasembled the swivels did you adjust the swivel preload?
if not there is your problem

I got the preloads reset when it was happening.