Whirring/scratching sound from rear under acceleration

[fsugatorbait]

Just picked up an 01 QX4 w/70k miles and under ~40% or more throttle there is a whirring/screeching type sound coming from the rear that happens at all speeds from take-off to passing on the hwy. If I modulate the throttle below apprx. 40% it goes away so I can basically replicate the problem at will and it is not dependant on the gear I'm in. I've done some searching and couldn't find anything. Anyone have any ideas? Thanks in advance.

Phil

[Big-Bird]

Didn't the QX's all have rear rotor brakes? Have you checked your rear brakes for mud, rocks, amount of brake material that remains? A sticky caliper can sometimes keep braking pressure on a rotor and cause premature wear on brake pads. There could easily be some metal to metal contact back there that could make the noise you describe. If that all checks out then there is only a few other items that coud be at fault.It's either a bearing noise or a drive shaft Universal Joint.

In the order of bearings: theres the transmission, rear pinion, axle bearings, or the carrier bearings for the ring and spider gears inside the differential. Have you checked the oil level and condition in the rear differential?

[KoukiS14]

dunno if it was changed in 01, but my 99.5 has drum brakes in the rear. A certain amount of whine is normal, but I'd have to really hear it to understand.

In the meantime, *bump*

[nissandoms47]

no R50s came with disc h233bs. Come to think of it, i think the only 233b that came with discs were on select WD21s.

[fsugatorbait]

Didn't the QX's all have rear rotor brakes? Have you checked your rear brakes for mud, rocks, amount of brake material that remains? A sticky caliper can sometimes keep braking pressure on a rotor and cause premature wear on brake pads. There could easily be some metal to metal contact back there that could make the noise you describe. If that all checks out then there is only a few other items that coud be at fault.It's either a bearing noise or a drive shaft Universal Joint.

In the order of bearings: theres the transmission, rear pinion, axle bearings, or the carrier bearings for the ring and spider gears inside the differential. Have you checked the oil level and condition in the rear differential?

Thanks for the response. The brakes are infact drums, but because the noise is only generated under ~%40 or more throttle and not while braking I'm going to throw that out. This condition also happens at low speeds in reverse.

I've been meaning to check, but the will the LSD equiped rear diffs operate fine with any LSD diff fluid? I have some left over Mitsu oil I used to change out the transfer case and rear diff with in my evo- both had LSDs.

Is there an access panel on the rear diff so I can check out the condition? When I looked the only thing I saw was the drain/fill plugs. Thanks for your time.

Phil