Truck is an 01' Sierra 2500 HD 6.0 L Fuel-infected 4WD. Problem I'm trying to solve is a "bouncing" felt and a faint thumping heard at speeds above 45 mph. After checking tires and struts, my next thought is the front axle wheel bearings. When I have the truck lifted and no weight on the suspension, the driver side wheel can be shaken a considerable amount more than the passenger side. I can see play where the front axle meets to the back of the hub assembly also.

Am I thinking right that this could be a bearing problem, or is there a CV joint in there that may be screwed up? If the bearing is the answer, what exactly am I getting myself into? Any help would be most appreciated.

Shrek

You wouldn't see any play in the wheel if the cv joint where bad. There shouldn't be any play in the wheel from a wheel bearing. After the wheel, caliper, and rotor are off its just a matter of removing the axle nut, unplugging the ABS harness, and removing the three bolts that hold the bearing to the knuckle. Its vitally important to torque the axle to the proper spec to increase the life of the new bearing. Go with a good quality bearing, this is not the time to shop with your wallet!! :)

Thanks for the response Airjer. If I shouldn't see any play from a front wheel bearing problem, any other ideas as to what my symptoms could be caused by?

I'm also hearing from repair shops that I can't replace just the wheel bearing on the truck that I have to do the whole hub assembly...I'm assuming they're full of it.

Shrek

No, you'll be replacing the hub assembly.

Lift the truck again with no weight on the suspension.
Make sure the steering wheel is locked (pull the ignition key and turn steering wheel until it locks). Try to get the steering wheel to lock in a fairly strait position.
Now, one at a time, go to each front wheel, grab the tire with your hands at the 9 o'clock and the 3 o'clock position, and push/pull with your arms to get the wheel to rock for and aft (front to back). If it feels loose or you can feel play in it, try grabbing the tire at the 12 o'clock and 6 o'clock position, and try to rock it up and down.
If you can feel looseness (or play) in both tests, then either it needs a new hub (bearing) or the axle retaining nut is loose.
If you feel looseness only when you do the for and aft (front to back) test, then it has a worn out inner or outer tie rod end.
If you feel looseness only when you do the up and down test, then it has a worn out upper or lower ball joint.

Hope this helps.

Oh, I forgot to add.
Bearings usually don't thump, they growl as you drive if they are going bad.
Ball joints and tie rods WILL thump when worn out and they can cause a bouncing or wobbly feel.
Bouncing above 45MPH can also be caused by out of balanced tires.

Your comment was very helpful quick69gto. This morning I went ahead and replaced the hub assembly. Something I did not mention before (because I thought it was unrelated) was that the ABS and Parking break dummy lights will randomly come on. (happens intermitantly, but once on they stay on til truck is shut off). No resistance is felt nor can anything be heard when this happens. My hope was that since the hub assembly came with a replacement ABS sensor that it would also solve that problem.

After changing the hub assembly the ABS dummy light will still come on randomly. The bouncing is better, but has not completely gone away. Now it does feel like an out of balance or simply bad tire (tires are Nitto A/T 285/75R16 which I've had trouble with bad rubber on before). The code for the ABS referenced a control module problem. From what I've learned this isn't something I want to play with and should leave it be if it's not causing any harm.

Was wondering if there is a tie rod problem if I would be able to move the tie rod seperately with the weight off the suspension? Would tie rod or ball joint problem also explain the alignment problem I've had for a while? (truck pulls enough to the right to exit most offramps hands-free).

Thanks again quick69gto and Airjer.

My 2006 just started doing the same thing.
I can't find out where it's coming from and it's driving me crazy!

Try swapping the two front tires (put the right front on the left front and the left front on the right front) and see if the vehicle pulls the other way. If it does or the pull goes away you have an issue called radial pull. You can solve that by replacing the tires.

I have michelen LTX tires on right now.
It's not pulling to either side, just thumping (not always) at speed.
Sometimes it will do it and sometimes it won't.
I have noticed that after hitting a ridge in the road (like where a bridge joins the road) it will do it.
It is only above 45 or so when it does it.

I am going to try the tire swap. Can't hurt

Would tie rod or ball joint problem also explain the alignment problem I've had for a while? (truck pulls enough to the right to exit most offramps hands-free).

I was referring to shrecks post about the pull.

My bad