Help Diagnosing a Thumping Sound in Driveline

[Glenn Goodrich]

I have a 2000 Mazda B4000, 4WD that is making a rotating thumping noise that sounds like it is coming from the front drivers side in 2WD. About 5 weeks ago I changed out both front wheel hub assemblies as one of them was bad after 120 k. Shortly after that the noise started. Thought it might have been one of the cheap oversees hubs I put in so I got a set of Timkens and put them in but the noise is still there. When accelerating it starts at like 22 mph and is real loud until like 40 or so when it gets drowned out because the wheels are going to fast. The noise is lounder when you are not accelerating and is still there with truck in neutral when coasting above 20mph on a smooth road. The noise is there when going straight on a smooth road and when turning the wheel hard left, but goes away when turning hard right. It also will come and go with the suspension flexing on a road that is not smooth and has dips, etc. Besides the hubs I rotated the tires, had the rotors turned, new pads but which made no difference. I also verified the front drive shaft and half shafts are not turning in 2WD to rule them out. There is no shaking in the steering wheel but sometimes you can feel the thumping in the floor board. Any ideas our suggestions would be appreciated, as this is driving me nuts!

[rockwerks]

How tight is the stub shaft axle nut? Maybe something stuck in the brake or a warped rotor?

[Glenn Goodrich]

Hi
This hub assembly does not use an axle nut, it has three mounting bolts that hold it in place. The half shaft goes thru the center of it and there is a retaining clip that holds it in place. Rotors were just resurfaced, and brake pads are new and nothing is hanging up.