Ever since I bought the car at 82k miles there has only been a noise when cruising from 40-60 MPH. It only occurs when I’m on the throttle (chalked it up to a noisy fuel pump for the longest time), but recently I’ve been getting concerned because I don’t cause further damage to my rear end. From my research I’ve narrowed it down to either an axel bearing or a pinion bearing. The pinion bearing looks like a simple job to do so I’m hoping it’s that.

Here’s a video of the noise https://youtube.com/shorts/6_0c_YGrxeM?feature=share
Interested to hear what you guys think.

Wheel bearing is a lot more likely, but it could even be a bad tire. (I don't hear good, so take that for what it's worth.) Pinion bearing isn't an easy repair; you have to re-set the gear mesh which is a pretty technical operation.

Best way to pinpoint it is to put the car up on stands (or a lift if you have access to one) and let it idle in gear. Poke around with a stethoscope til you find it.

The relative dimensions of the pinion to the axle housing centerline are independent of the bearings.

That said, the shim pack is reused and "resetting the gear mesh" is unnecessary. Only need to install a new seal, new crush sleeve, and set bearing preload.

Only need to reset when the gear set, differential, or axle housing is changed.

I had a whine on coast it wasn’t bad. Just for the heck of it I changed the oil in the rear end. Never heard the whine again.

I just got a 2004 MGM with 100k. About 2 weeks ago I finally got around to changing the rear differential fluid and I was surprised the oil was near dark brown to near black in color. It even left a stain on the differential cover.

Changed out the fluid with fresh new Amsoil severe gear 75w140.


In your case go to Walmart and buy some Supertech gear oil and change out the fluid and see what it does. If that doesn't work then knock out those bearings (easy fix just need to rent a tool from Autozone) but if it's anything else in the differential I would take that to a shop that specializes in transmissions or racing.

I serviced the diff fluid about 10k miles ago while the noise was still going on, didn't fix it. I should note that there was minimal metal particles on the fill plug when I pulled it off.

My '11 Vic had your exact symptoms to a "T," ended up being the pinion bearing (as expected.)

Gave me a good excuse to swap in a lower ratio.

Usually when people tell me it was their pinion bearing they always follow it up by “I swapped in a (enter bigger rear gear ratio here) and that fixed the problem” lol, nothing wrong with this, but my question is, if the pinion bearing is bad, is it too late? Or can I just get away with replacing the pinion bearing itself?

You can replace just the bearings.

Do you remember if it was your inner or outer pinion bearing that failed?

Since you said you hear the noise while cruising, and NOT upon deceleration, that would indicate that it is your outer pinion bearing (if it is indeed a pinion bearing noise).

Either way, you replace those as a set, which will require disassembly of the differential.
Good luck getting that bearing race out any other way.

Might as well replace all the other bearings while you're at it.
And go to a lower gear ratio.

I just ordered the outer bearing and we’ll see if that fixes it. If I have to pull apart the diff to fix the noise I’m not putting the stock 2.73s back in.

So how are you going to get the race out? If that bearing is bad, the race will be trashed, too.

Not sure, I guess if it’s scored really bad I’ll have take a trip to the junkyard and look for an explorer rear end

Hey, I am jumping in on this, I bought a 2010 and have a very slight but noticeable mid to high pitch whine and a noticeable vibration/shudder under certain loads and deceleration. I am pretty confident it is drivetrain and coming from mid ships or back. I have had wheel bearing fail and don't think that is the issue.

I am wanting to get it up on a rack but would like to know if this is likely a pinion seal? And judging by other posts, change out diff fluid. Anything else to check?

Any tell tale evidence that the pinion seal has failed. Will it leak? Thanks!!!