High-Pitched Noise

[a.p.barron]

Since this is a different problem from the previous one, I decided to make a new thread. It's continued from here: code-51-problem-t522664.html

Basically, I got my car taken in for a 90k service, and now it makes a high-pitched whining noise. The mechanic told me it's most likely coming from the differential, and after some advice from some people on this forum, I still can't figure it out. Ace2cool suggested that it might be the driveshaft carrier bearing, but when I got down there and tried to move things around, everything was solid. Robomatic12 suggested that it may be a wheel bearing, and after weaving around like an idiot in an empty parking lot, the noise didn't change. So, here's a video capturing the noise. Hopefully it'll give you guys a better idea of what I'm talking about:

http://www.youtube.com/watch?v=3s34QZ_eWx8

It's best heard with headphones. Sorry about the quality, it's kind of hard to steer and shift with one hand. :p

[asoomal]

Does it get louder under load?

[a.p.barron]

Well if you watch the video, you'll notice that it gets higher-pitched as I speed up and lower-pitched as I slow down. It seems most noticeable (louder) when I'm slowing down though.

[robomatic12]

I watched the video, its hard to seperate the exhaust from the whine. How is your transmission fluid level/color? Are you AT or MT?

As for testing the rear wheel bearings, you should do a steady weave left to right at cruising speed, doing it in a parking lot probably won't tell you much.

Get somone with an experienced ear to take a look, that will prevent any false diagnosis

[a.p.barron]

I'm MT, and I'm not sure, I'll have to check it out. The mechanic I took it to told me he put Reline MT-90 in it, so it shouldn't be having any problems.

Thanks for the heads up, I'll try weaving tomorrow in the morning, since there are no people on the roads.

Man, I'm kind of irritated right now because I spent a lot of money to get this thing "fixed," but it seems like some of the issues that would have been fixed with a 90k service are still there, plus I get to have new issues. :-\

Anyway, here's another video. Around the 10 second mark, you should be able to hear the high-pitched sounds very clearly. Let me know what you guys think.

http://www.youtube.com/watch?v=8HEXsqPR71U

[asoomal]

That sounds like the differntial howling to me...

[BigTDogg (MA)]

Yep, flush the fluid out with some Redline 75W-90 and see how it sounds.

[a.p.barron]

So I went ahead and changed the diff fluid to Redline 75W-90, and unfortunately, it's still doing it. :-( I also went ahead and did some weaving at around 15 - 45 mph, and the sound didn't change.

Any ideas?

Also, just to make 100% sure, the N/A 300ZX has a VLSD, right? Or does it have an open diff like the 240SX?

[robomatic12]

VLSD in the n/a 300zx.

[a.p.barron]

Yea, that's what I thought.

Thanks.

[robomatic12]

Was there a large amount of metal shavings on the drain plug magnet of the rear diff?

[a.p.barron]

Nope, no metal shavings.

I'm starting to think that it's one of the bearings inside the differential. You think that might be a possibility?

[nissanfreak12]

Im just gonna throw this out there, how are your tires? When I had some go bad, they made a similiar howl, just a thought.

[a.p.barron]

That's actually a good suggestion and the first thing I checked. I just got brand new tires, and I thought they might have been overinflated, so I checked everything out, but the tires were at the proper levels. Could it be that tread on the tires are causing this? Here are the tires that I have:

http://www.onlinetires.com/products/veh ... s+96v.html

[nissanfreak12]

try rotating and see what happens, its possible you have tread seperating, but if thats the case, you will notice other issues. Worth a shot, and the tread is similar to what I have, when I can drive it, it sounds good

[gowhoosh]

I can't watch the video right now because I'm on a government computer, but it sounds to me like you are having the same problem as me. The squeal is annoying as hell, very loud, and only noticeable under load. If I'm cruising and it's screaming at me, as soon as I push in the clutch or let off the gas it goes away. I replaced my Goodyear Eagle F1's which were balding with Falken RT-615K's, and the noise didn't change. I replaced the Center Support Bearing/Carrier Bearing/Midshaft Bearing with an OEM replacement, as the old one was shot, and no change. I replaced the right (passenger side) rear wheel bearing (what the previous owner's mechanic had declared the problem as) with a new OEM one, but it didn't help in the slightest. I attempted to change the diff oil but stripped the drain plug, but I believe that's the next logical step before tearing apart the diff and breaking out gear marker. As I assume it is with yours, the sound in mine is VERY hard to locate. I have a 2 seater, and have had multiple passengers try to move around and narrow down the source of the squeal, to no avail. I have had a friend drive it on a 4 point lift, alternating from 60 to 80 mph every few seconds, as I was underneath hunting, but it didn't make a sound at all; it only is noisy under load, which leads me to the differential. Although it does sound like the rear of the car, I'm not eliminating the transmission as I think my synchros are bad, on top of [most likely] 120k miles on it. If I figure it out before you, I'll make sure to post on here with the solution. Good luck man.

[nissanfreak12]

Honestly A.p.baron, the best thing you can do is lift the rear of the car off the ground, put i on jack stands and has the wheels spin till you get the noise. This way you can almos isolate the noise better instead of "its coming from the rear". Now this is very dangerous, just make sure you use jackstands and even keep the jack up by the diff for a just in case. Have a second person there if you can "driving it", while you hang out in the back so hopefully you get a better idea where its coming from.

[a.p.barron]

Yea, that does sound pretty dangerous. It also sounds like something that would get me kicked out of where I live, haha. :P Thanks for the suggestion though.

I just ended up buying another diff from a fellow Z enthusiast. Hopefully when I get it installed, everything will be as smooth as butter. :-) If not, then I'm going to be pissed/annoyed/broke. :-\

[nissanfreak12]

I hope that works, i really feel your pain about not being able to figure out the issue. Good luck to you, definitely keep us posted.

[nissanfreak12]

Any word if a different diff worked? or have you had time to install?

[a.p.barron]

It's been a combination of not having any time and the bad weather. I will definitely post up what happens though.

[nissanfreak12]

[a.p.barron]

So I finally got the diff replaced. It was definitely the bearings inside the diff. When I tried to spin all the parts on the diff that I bought, everything was smooth and there was no noise. When I tried to spin all the parts on the old one after it was uninstalled, it was super rough and hard to spin. Now, there is no more noise, and it feels like my car has a little more pep, since it doesn't have to work as hard to spin the tires.