Does it have runout with a drill in the chuck or the chuck itself? The reason I ask is that some chucks will "look" like they have runout but a drill bit actually will run straight. If the drill bit has runout then you could have dirt in the quill (between the quill and the arbor) causing it to runout or the jaws in the chuck can be bad from too many drill bits being spun in them. Or something could have caught at one time while drilling, flung it around and actually bent something. My guess would be the chuck is just worn out. The chucks can be rebuilt but with so many companies out there it is almost cost prohibitive to buy a rebuild kit anymore. That is if they even have them on the market for your brand of chuck. There are a few rebuild kits out there. Jacobs I know has kits for virtually every one of their chucks. Enco has some reasonable chucks as do some other companies. Travers is another.