Front end grinding

Tiny
DENNIS79
  • MEMBER
  • 1999 GMC YUKON
  • 15,000 MILES
Hi I just bought a 99 yukon denali with 150,000 miles on it, got it at a very good price. When I test drove it I noticed a grinding noise up front, so once I purched it frist thing I did was replace front rotors and pads, tthe noise is still there. So I had someone look at it and he ssid my right side hub asembly was bad, so I replaced it. The noise was still there plus now I hear a grinding in the rear, I heard befor that noise can travel from the rear. So I replaced the rear brakes, well my breaks work great now but the noise is still there. It is a grinding noise from up front, it seems to be when I let off the gas to coast it grinds, or when I hit the breaks it grinds and when I put it in four wheel drive the noise gets louder and is full time. Someone told me it might be the front differential. Please help me. Thank you!
Tuesday, January 10th, 2012 AT 4:02 AM

3 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 34,330 POSTS
Do you have cv joints or universal joints in the front by the rotors?

There is a tool you might be able to borrow or rent from an auto parts store that borrows them called the "Chassis Ear". It is a set of six microphones, a switch box, and headphones. You clip the microphones to suspect points, then drive around while listening with the headphones. You can move the microphones around to zero in on the source of the noise. Be aware that many mechanics have never seen or even heard of this tool. Suspension and alignment mechanics use it to find rattles, squeaks, and other noises.
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Tuesday, January 10th, 2012 AT 4:13 AM
Tiny
CARADIODOC
  • MECHANIC
  • 34,330 POSTS
Be aware too that one-piece wheel bearing assemblies require a very high torque on the axle nut, in the area of 180 to 240 foot pounds. I stick a screwdriver into a slot in the rotor to keep it from turning while I tighten it to that value, but many people who don't think of that set the vehicle down with the weight on the tire to keep the axle from turning. That is too late. There must never be any vehicle weight on the bearing when that nut is not fully tightened. Doing so will instantly damage it and make it noisy. It will sound like the buzzing of an airplane engine.
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Tuesday, January 10th, 2012 AT 4:17 AM
Tiny
FACTORYJACK
  • MECHANIC
  • 4,159 POSTS
Pull the front differential drain plug, it has a magnet on it. Check the oil for a metallic appearance, check the plug for debris. It probably would not hurt to service the rear differential as well.
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Tuesday, January 10th, 2012 AT 4:29 AM

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