Drivetrain whirring then clunk, normal

My 97 4.0 4X4 gets a drivetrain whir noise, then I hit the brake and it clunks and the noise goes away, for awhile. The driveshaft is tight, with no play in the u joints. The front shaft has half inch play when it is in 2 wheel drive. I just had new Ford lockout front hubs installed. Any ideas?

Ok, took it back to the shop, and they said there was some gunk from the old hub in there, and cleaned it out. Now the ABS dash light came on. is it possible they got "gunk" in the brake rotors and it messed them up and that's the noise I'm hearing now that the ABS light is on?