I have a ’99 Blazer 4x4 4d (4.3 engine) with some drive train noises/issues. At slow speeds (under 20 mph) I hear a thump… thump… thump from the front passenger side axle/hub. Once up to a reasonable speed, I do not hear it. Occasionally when I stop (or start from a stop) I hear a pop from the front drivers side axle/hub. My brakes and tires are fairly new. Does this sound like bad hubs? Any comments or suggestions would be appreciated. Thanks.

Jeremy

 

Pops are typically front ball joints. Check the ball joints by jacking up the front of the vehicle and supporting it on jack stands. Now take a fairly long 2x4 and put it on edge under the wheel with one end about a foot behind the wheel and lift up on the other end, listening and watching the lower ball joint for movement (you may need to turn the wheel out to get a good view. The upper ball joint can be checked with a pry bar between the steering upright and the upper a-arm.

Cyclic thumps will probably be a bearing. With a 4wd vehicle, front wheel bearings can be difficult to check due to all of the other things that spin at the same time at the front wheel. Sometimes you can feel a bearing problem by putting your hands at 12 & 6 o'clock and alternately pushing at the top/bottom and pulling at the bottom/top. If play is felt, the bearing is shot. However, the bearing may still be bad even if it doesn't have any play. This can occur when the bearing surfaces pit. This would cause the bearing to run rough. As I illuded to previously, this can be a difficult thing to narrow down as there is quite a bit of drag on the system due to the other components that are all linked together. You may have to remove the wheel, caliper/bracket, and brake rotor to be able to detect a roughness in the turning of the bearing/hub.

Hope this helps!!