Unitized Bearings

Hi everyone. Got a stumper here....I installed unitized bearings on my brothers 2001 Grand Prix. I did both sides. The rumble is gone but now it has developed a mysterious knocking sound from both sides. If you turn the wheel with the vehicle rolling at idle speed the knocking sound can be heard alternating from side to side. I put my hand on the rim and it almost feels like a binding whereas it is catching and letting go. I disassembled everything to make sure I installed correctly and everthing looks fine. The bearings were purchased from Autozone and when I disassembled them they seemed fine. When I removed the old ones they came out in pieces so I was curious if by some chance there is another part that I am missing. As it is now the new bearing that is encased in blue plastic directly mates to the c.v. joint spline. The bearing is not a friction fit to the hole in the spindle unlike the one that I removed. Am I missing something? I know it has been 11 years since I worked on cars proffesionally but I have never ran into this before on a bearing replace. Please help so my brother doesn't disown me!! HA HA Thanks in advance

Make absolutely certain that you have the axle shafts torqued to the right spec and that you used new axle nuts. This is a common problem and is usually traced back to improper torque which allows the shafts to move back and forth when turning.

I hope you didn't use an impact wrench on the axle nut, if you did, you probably destroyed the ABS sensor and ruined the bearings. Axle nut torque is essential, as it pre-loads the hub and keeps the axle from shifting as GTP said. If you bought the "white box" cheapest model A-Z sells, they are JUNK and may be the whole problem. Make sure you follow the hub manufacturer's axle nut torque spec if it differs from OEM or a repair manual spec, as changes in hub design may necessitate a new torque spec to properly pre-load the bearing.

It's the same old horror story over and over again. Where have we heard this before Rich and GTPDad.

I can't emphasize more than say stay with OEM GM/AC Delco parts, especially for the hubs and bearings. I learned that a long time ago even if it means going to a boneyard and pulling the parts. The higher cost of GM OEM parts is worth it, especially in the long run and precluding a situation such as this. Oh well.







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I 've had good luck with NAPA premium bearings, but you guys are dead on about the Chinese stuff and proper torquing here, most people don't have an over 150 torque wrench or don't do it on the ground, big issues here.

i just bought the hub assembly for my car.. The brand is national. It didnt give tourqe specs, so i assume the factory specs apply....also thanks GTPDAD for letting me know to get a new axle nut too... The axle boot is not cracked on my car...at this point , during this job could i replace the boot to be safe?

Thanks all for the replies!!! Took these bearings back and purchased the OEM bearings. Will try to locate new axle nuts. Dealer said they dont normally stock them but they can order them. Thanks again for all the feedback!!!! Mike

Regalfriend, to answer your question as long as the boot is in good shape I wouldn't worry about it. Most boots will last the life of the axle shaft as long as something doesn't tear it like hard snow or other foreign objects. If you notice a tear or grease coming from the boot then repack and change.

Thanks GTPDAD...i kind of live on the side of caution....to replace the hub requires me to take off a few items like tire, brakes, etc. Usually when i get to this point i like to replace everything like new.,,.. It would bug me if i did the hub and a few months later i had to do the axle or boot. On the other hand if the OEM boot is good and i replace with an aftermarket i wouldnt feel %100 confidant...i dont think many aftermarket parts are as good as OEM. However if i had a job to replace the caliper i may go as far to replace the brake hose too...at this point since i have to bleed the brakes for the caliper i might as well put a new hose on too

Hi everyone. Got a stumper here....I installed unitized bearings on my brothers 2001 Grand Prix. I did both sides. The rumble is gone but now it has developed a mysterious knocking sound from both sides. If you turn the wheel with the vehicle rolling at idle speed the knocking sound can be heard alternating from side to side. I put my hand on the rim and it almost feels like a binding whereas it is catching and letting go. I disassembled everything to make sure I installed correctly and everthing looks fine. The bearings were purchased from Autozone and when I disassembled them they seemed fine. When I removed the old ones they came out in pieces so I was curious if by some chance there is another part that I am missing. As it is now the new bearing that is encased in blue plastic directly mates to the c.v. joint spline. The bearing is not a friction fit to the hole in the spindle unlike the one that I removed. Am I missing something? I know it has been 11 years since I worked on cars proffesionally but I have never ran into this before on a bearing replace. Please help so my brother doesn't disown me!! HA HA Thanks in advance
Had the same problem couple weeks ago. I couldn't figure out what was that noise. My mechanic helped me and guys in this forum. I bought the cheapest bearings from Advance Auto Parts. They are not the right ones for GP. Just return them and tell them to get you those more expensive ones. Replace them and knocking sound will disappar. Good luck