99 QX4 Rear End Whine/Howl..Should I Fix It?

[Joe99qx4]

Hello..I've owned my 99 QX4 for about 4 years. About 2 to 3 years ago ( or maybe even when I bought it) I've noticed a whine or howl coming from the rear that you can only hear at 40 - 55 MPH. I never really thought anything of it and just thought this was a normal truck noise. You can hear the whine mainly when you are cruising between 40 - 55, it quiets down a little bit during acceleration and disappears when you get off the gas and your coasting. I put about 50,000 miles on it ( now has 145,000) and I've never changed the diff oil. I changed the oil yesterday and the oil looked good. It had a gold-ish motor oil looking color to it, nothing in it. The drain plug is magnetic and there was a small amount of fine particles on the plug; looked like "gray grease". I put 3 quarts of mobile 1 75w-90 oil back in. Still have noise. Diff is LSD.

I've read that this is the pinion bearing or gear making this noise. I brought the truck to a friend who is a good mechanic and he said the same thing. We put the Q on the lift and checked it out. There is no side to side play at the diff what so ever. He then spun the wheels and there is hardly any play or backlash.All appeared good from looking at it on the lift. If I'm not mistaking, there is no inspection cover.

Maybe its another bearing.I have a couple questions.

1. Would axle wheel bearings cause this noise?
2. If it's a diff problem, what is a fair price to replace bearings, provided no gears need replacing?
3. Should I even bother messing with it? I hear that sometimes you cause other ssues by taking these things apart.It's been doing the same noise for years. Is this maybe a "normal" noise for this truck?
4. Could I put a heavier weight oil in?

Thanks in advance for the help, Joe.

[Towncivilian]

I'm afraid I don't know too much about the internal workings of differentials.

Have you confirmed that the differential is indeed making the noise? Fuel pumps can make a whining noise sometimes. Have you ever changed the fuel filter? A partially restricted filter can make the fuel pump work harder and thus perhaps louder.

Depending on your climate, a xxW-140 grade gear oil is usable. Where do you live? Amsoil also makes a 75W-110 fluid.

[Joe99qx4]

thanks. I've changed the fuel filter about 8 months ago, and noise has been there before and after the change. I live is hot, humid Florida, so I think I would be OK with going with a heavier oil, or at least a mixture of 75w-90 and 75w-140. I really don't want to dump the money into the rear end (obviously) if it's going to keep going, but there is no way for me to know this. Then again, the fact that is has been doing this for 3 years and the oil looks good and no "pieces" of metal came out during the drain makes me think everything is OK. I was more curious to see if any other pathfinder/QX4 owners have any experience with my problem/symptoms.

[Towncivilian]

I'd think you'd be fine running 140wt gear oil in Florida, it's definitely hot enough down here. Where are you located in Florida?

[Joe99qx4]

I'm in St. Petersburg. I would like to bring the Q to someone who just specializes in this type of stuff. My friend/ mechanic said there is a possibility the howl won't go away if the bearings are replaced because the gears wear a certain way. Not sure..

[Joe99qx4]

Has anyone had a pinion bearing replaced and the cost on Q or Pathy?

[Joe99qx4]

So I brought the Q to a local repair shop that does NOTHING but work on differentials. Alan Gear works in Clearwater, Florida. He took the car for a drive and basically said this:

The noise I hear from 40 - 55 MPH is gear whine. He says I could put after market gears in there, but they might wine just as bad as the OEM that is in there now. The OEM gears alone are $500 +. He says that since the noise is only between 40 - 55, it's not the bearing, as the bearing spins as soon as the car is in motion and I would hear the noise all the time. He says basically, I could get another 50,000 miles out of it just the way it is and he recommended leaving it alone, as he did not feel there was a major issue. He told me if the noise got louder or started to sound different that maybe it's time to fix. He also suggested checking the oil and replacing it maybe once or twice a year will help.

What he said makes sense to me and it's the same thing I've read on other forums. Since it's been making this same noise for years, I think I will leave it alone. If I do ever fix it, it seems that maybe a low mileage, center might be the way to go.

[Towncivilian]

Thanks for sharing your findings with us. I'd definitely stay on top of fluid changes.

If you ever do replace it, I'd upgrade to a 4.636 ratio differential if you're not already running one. Look at the certification plate on the passenger side firewall; if it says HG43, you have a 4.363 ratio; HG46 is 4.636.

[Joe99qx4]

I will check.

Question. In the future, I may replace the differential with a used, low mileage one. I'm assuming I have a locking differential? I have a switch to put in 2wheel mode, auto mode or lock. I just want to make sure I buy the correct one.

[Towncivilian]

No, our rear differentials are either open or LSD, not locking. You have an auto mode transfer case.

[Joe99qx4]

Ok.. Thanks. I have the LSD and the 4.6 gear setup

[cmoliver63]

I have exact problem ( I think 2001 Pathfinder) how did you resolve issue? I even have the 45-55MPH whine

[Joe99qx4]

Three years later at 180,000 miles. Still making the noise, never had it fixed, no issues. Will drive it until it dies.

I would just make sure to check your oil in your differential for metal pieces or flakes.