auto locking hubs

Well here's a challenging, and most likely an expensive job, So I have two problems that could be one major problem. Problem one: when I turn my ABS light sometimes comes on and there is a slight shimmy when I'm going down a hill. Nothing crazy, so I havent paided much attention to it...

Ok Ive gone through a lot of threads here and cannot find an answer to my question. I have a 2001 F250 7.3 Diesel. I just replaced both auto locking hubs and wheel bearings. All tested fine and according to my mechanic, all is working normally. I want to know if 4WD low engagement is the...