I need a little help diagnosing a Rear End Noise in my 2002 A4 Coupe.

NOT TIRE NOISE - Replaced Rear tires (TOYO T1R 295/35/18) with same tires - as old ones were almost Slick. NO CHANGE.

Noise is SPEED (MPH) Related - NOT RPM or gear specific.

It sounds like a BRRRRR or Whirring noise that increases in pitch with speed increase. Begin to hear it at 15 - 20 MPH and gets drowned out by exhaust (Borla Stingers) and Road noise at 70.

Noise is NOT the high pitched sound of a ring and pinion with the loading and unloading sound you get when on and off the gas.

Noise decreases in sweeping left turns and increases in turns to the right.

Noise appears to be coming from left rear to center (confirmed by son riding under hatch.

Jacked rear of car - no visible signs of damage, rear end oil leakage or grease from CV joints. ( I had rear lube checked and changed earlier with no change in noise)

Checked for play in wheel bearings on both sides - none felt.

Ran car with rear in the air (up to 70 MPH) and NO NOISE heard at all.

Figure problem must be Wheel Bearing (HUB), CV Axle or maybe Rear End output (AXLE) Bearing. Would like to confirm problem before buying parts . Can do axle and Hub myself - REAR End is different story.

Any thoughts or suggestions on proper diagnosis?

Who would be a good local "GO TO GUY or SHOP" in the El Cajon / San Diego area.

Thanks,

Phil Smith

 

I would say wheel bearing, but you said you aren't getting noise when you had it on stands and ran it at 70.....

 

No mention of you recently changing to different wheels/spacers or different rotors.
If any of the above, make sure the sprokes of the wheels are not clicking against the calipers.

Check to make sure that the emergency brake line that goes to the back part of the wheel/hub area is still hooked onto p/brakelever & not rubbing/hitting against anything.


I really don't think this would be the problem, but it would not take long to check. Some times the axle splines become rusty & start making a
noise back there in that area. In order to eliminate .Try this...

Pull the wheel off on the side that the noise is coming from.
Check to make sure the axle nut is @ propper torque value.
If axle nut is @ propper value, remove the nut & spray some light lubricant heavily into the axle splines,from both sides
(inboard & outboard) & retorque.

 

It's your LR hub bearing. When you have it on jacks, there is no load on the bearing and it will be quiet.

 

not entirely true.

 

Then what is the truth, in it's entirety?

 

I've heard multiple wheel bearings roar when on a lift. depending on how bad it is though, sometimes you need to use a stethoscope to really hear it.

 

Left REAR HUB replaced - NOISE GONE!!!

With rear off the ground the only way to hear it was with a long screw driver carefully held against the hub with wheel rotating.


Thanks for all the inputs / suggestions.



Phil

 

Glad you were able to locate & fix the problem
Thanks for sharing with the forum what the problem ended up being & how you fixed it.

ragtopws6 (Rick) early diognosis was right on the money as usual.

 

Thanks! I see these on regular bases.

 

Rick knows his stuff, love my rebuild, the 3.90 gears really woke this car up!!!!

 

I seem to be having a similar problem. You can hear a rubbing / humming noise from rear end at about 30 mph and above, the noise stays when in neutral, Had the tires and alignment checked, jacked up the rear and you could still hear it. Right now i'm trying to decide between Torque tube couplers, rear hub, bearings, Differential ???? I havnt been able to narrow it down to a specific side, that is if it is even coming from a specific side.