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2006 Acura MDX, grinding noise in rear of car

2006 MDX with 88k miles. It’s not all the time but there’s a metal on metal grinding noise in the rear of the car at times. I never hear it when braking. I hear it mostly when turning right and accelerating. Such as turns, curves, etc. I’ve pulled the tires off and brakes and all parts appear good. Don’t see what it could be. Any help appreciated!

The most common cause for that as reported here seems to be that the brake pads are worn and the brake pad wear warning gadget is scraping metal against metal. It’s supposed to do that, to alert the driver the brake pads need replacing. But you say the brake pads are not worn and everything w/the brakes looks fine? hmm…

Let’s get some basic questions out of the way. How is your car’s drive system configured? AWD? FWD? RWD? Have you checked for abnormal play in the rear wheels by pushing/pulling/twisting with the car jacked up? And have you listened for any weird noises while manually turning the wheels? Since it occurs more when turning right, focus att’n on the left rear wheel. That one gets the most force put on it when turning right.

If none of that pans out, it might be something to do w/the suspension system. When you accelerate the front of the car goes up, and the rear goes down, so a suspension problem might make a noise then, and while turning. Usually it would make a noise when stopping for a similar reason, but not always.

Has the gear oil been changed in the rear differential? There is a manufacture specific additive in the gear oil that becomes depleted with use and can cause a chatter in the differential when turning.

2001 MDX With 90K miles. It started slow, but now if more consistent and a bit more noisy

Lets say the car is parked. I can start driving straight, forward or back, no problems,

But if the wheels are turned, either right of left then when I start moving the car I hear a grinding noise in the rear of the car. It only makes the noise when accelerating. If I am turning and accelerating I hear the grinding, but the second I lift my foot from the accelerator pedal the noise disappears.

First thing we looked at was the ball bearings, which are ok. Now my mechanic is suggesting I change the Oil in the differential
I’ll keep you posted after I do.

Replaced Differential FLUID and the noise is gone. I wrote FLUID, because different brands use different type of oil. So I used The one the Dealer sells

Found this on another place, Instructions to replace Differencial Fluid. Even if you dont do it yourself, I’d say read it, so when you take your car to a place to have this thing done you know a little about it and they dont charge you too much

Yeah if its coming from the differential-It’s supposed to be changed the first 10,000 miles, then at 30K intervals along with the transmission and transfer case if its an AWD. It doesn’t say that in the book and won’t come up on the magic maintenance minder, but that’s what was covered in the owner’s class. Very expensive if that’s what it is.

Replaced the Differential Oil and the grinding noise is no longer there

Was the fluid level low then? Did you sieve what fluid came out for signs of metal debris?

I had it done, so I dont know, I will ask, is good to know this information

Some of the rear differential gears rotate only during turns, so it makes sense you only heard the noise during turns. The typical reason for that is the gear oil is low for some reason. Suggest to monitor the gear oil level every month for 6 months or so to make sure whatever caused it to go low isn’t still happening. I had a friend years ago w/a Chevy Blazer who – preparing for a cross country drive from New York to Reno – had the rear diff gear oil changed and the shop forgot to install the drain plug. Somewhere around Denver that noise started. As you might expect this story doesn’t have a happy ending.

It is common with some limited-slip differentials to develop clutch chatter after the additives in the fluid degrade, there is no reason to go snooping around for a mechanical failure since the noise is gone. Also if the differential was leaking your mechanic should have recommended to repair the leak so I doubt the fluid was low and leaking.

Thing is you’ve got to pump the stuff in and not easy at all to just check unless you get it on a lift. When I had mine done, the book said it held 1 1/2 quarts or somewhere around that and I got charged for four quarts. They really had no answer when I asked about it so I just suspect the book was wrong.



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Maybe the shop carries that specific differential fluid in 1 gallon quantities . . . hence you were charged 4 quarts?

Or the book was just wrong, as you said. I’ve encountered numerous vehicles in which the actual fluid capacity is considerably more than what the owner’s manual says

Yeah they’re pretty honest people but I was a little surprised at the $120 charge so decided to share my surprise. Still 1 1/2 quarts doesn’t seem like much for the differential.

I don’t know what year your MDX is, the 2014 show 2.7 quarts for the rear differential and 1/2 quart for the transfer assembly.