I have had this 02 ZR2 for about 6 months now. Just recently I have been getting a rotating grinding noise from the left rear of the vehicle. It makes this sound during hard braking and when I do a clover leaf exit at speed. Removed the tire from the suspected area fully expecting to find the pads into the rotor or park brake shoe worn out. To my surprise everything on that side has been replaced (pads, park shoe, rotor, retainers and caliper) no trace of anything interfering with something else. Got the stethoscope out ran it in drive and listen to the areas where the bearings are but didn’t hear anything. I suspect someone replaced the brakes thinking that the grinding noise was associated with brake parts.

I guarantee anyone who was to drive this would immediately conclude it was a brake issue just from sound alone. The only thing that puzzles me is the grinding noise is rotating (shoop,shoop,shoop). If anyone has experienced this before and can point me in a direction to look it will be greatly appreciated.

UPDATE
I am the dumbest person in the world. Every time I have looked at this I used lift in my welding shop, the suspension drops so I didn't notice THE EFFING MUDFLAP WAS LOOSE AND RUBBING THE TIRE. OOOOOMG

 

Raise the truck to get the tire off the ground and move it up and down to see how much play is in the axle bearing. And leakage around the axle seal?


George

 

No seal leak and minimal side to side, maybe .020 which I assumed was within tolerance.

 

The shoop shoop noise makes me think wheelbearing.. but that doesn't seem like excessive play in it. How's your backing plate look? Is it bent or rusted and stuck in the caliper a little bit?

I'd try to spin it by hand and listen/search out the noise, maybe have someone lightly press the brakes while you do.

Another thought is a warped rotor hitting the backing plate or something else.

 

Are the leaf spring shackles and bushings in good condition? I'm thinking of things that become misaligned during that particular force. Braking while turning right makes me think of driver's front wheel bearing. I thought my noise was coming from the rear but I changed the front bearing hoping to be lucky. I found chipped spider gears in the rear diff. Yours being a zr2 has an 8.625 gov loc which means no spider gears. I'd pull the rear diff cover and check for debris. Changing the lube and inspecting the gears isn't a bad idea anyway since the truck is new to you.

 

Yea, I'm thinking axle bearing as well. May start looking for a locking rear diff.

 

8.625 gov loc? please expand on this.

 

GM put 2 rear differentials in blazers. A 7.625" ring gear that came open (one wheel peel) and gov loc (factory posi). And a heavier duty 8.625" that for a zr2 is posi.

 

I just figured that when I spin one wheel and the other turns in the other direction it was an open.......RPO code?

 

RPO code G80. This design is only posi when slippage engages it.