Differential Noise
 

Anyone here thinks the differential is a bit noisy in the following conditions?

1. Highway cruising 75 MPH, 6th gear, gas pedal very slightly open as to keep the speed. (Some sort of annoying high pitch noise is heard)

2. Street cruising 40 MPH, 4th gear, gas pedal slightly open as to keep speed. (Annoying high pitch noise)

I am assuming it is from the differential but cannot be 100% sure.

I would love any help in this matter.

I took it to the dealership and they said it was normal noise yet I went to test drive another Z and though there is a similar background noise it is not even closely as pronounced...

I can hear some differential whine in my Touring non-LSD when driving slowly and decelerating under engine braking. One way to quiet it down is to swap the OEM fluid for some sythetic gear fluid like Redline Differential Fluid, that is what I plan to do if it gets worse anyway.

I'll have the fluid replaced. Hopefully it will help.

Agreed, the fluid in my differential was some kind of horrible, nasty jet black after only 12k miles and I dont track my car or do burnouts.

Bought two quarts of Redline 75W-90 (not MT-90) and two new differential bolt washers to be safe. Had no trouble draining the crud out and filling her up with good fluid.

DIY is here: http://www.the370z.com/diy-section-d...il-change.html

Fluid options are here: http://www.the370z.com/engine-drivet...scussions.html


Also, its worth noting that while the 2009 Owners manual asks for Super Hypoid 80W-90 Gear oil (GL-5), the 2010 manual says to use synthetic 75W-90 GL-5 gear oil. Logic says there is a reason it was changed so I would go with a nice synthetic 75W-90 GL-5 gear oil like Redline, Motul Gear 300, etc.

ECU whine?

It's unlikely as the whine changes pitch and tones depending on RPM.

Now that I think about it, if it is depending on RPM it may not be the differential...

I am back to square one then. Maybe some gears. I am going to try to make a video and see if I can hear the noise in it.

All I am pretty sure about is that it does not come from the engine.

it probably is the differential the noise increases with wheel speed, it's just a combination of when the exhaust is quiet enough that you can hear it that makes it seem like it comes and goes. I have alluminum bushings on my diff so it gets really obvious and it is the worst at 40 and 70, because the engine is quiet at those speeds and the differential is under load when you have the gas on so it is loudest while just maintaining speed at slow speeds it's quiet enough that you can't hear it. I would say if it annoys you take it in and see if they want to pull the cover and use some redlead to check the gear mesh and back lash.

I have the same issue.

I can hear the a repetative noise at 40mph and at 60-65mph. It doesn't matter what gear you are in. The noise comes from the rear of the car. I can turn the radio up but the frequency cuts through the music. It sounds like a baby going wah wah wah wah over and over.

I have 2010 base.

I complained to the dealer about it already but they said they heard no noise.

Does any body else experienced this?

The dealership did hear the noise on my side but said they compared it with another car and it was the same therefore they say it's normal. The question here is are we talking about the same noise, not sure but if it is and other people don't have it then we have an issue.

The noise from the diff is "normal" in the sense that all the z's have it. It's apparently due to the baklash specs for the gears.

Describe the noise you are talking about?

My noise is definatly coming from the rear drivetrain.

I am taking my car into a different dealer on monday and having them take a look.

Dose any one notice a difference with changing the diff oil to a higher quality synthetic?

You can look at my first post. I am the OP, I describe the noise.

I was told by Stillen to not change the differential oil too soon. It's best to keep the factory one for the first few thousand miles but I will change it to a high quality one after 5K.

Any auto guys having this problem or just the MT's?

Anyone know what the service interval is for the diff offhand -- is there one?

Fluid swap at 30k miles. i do mine every 10k given how nasty it looks.


As for the noise, it's either the ECU or your fuel pump. The ECU is in the passenger footwell. You should hear the whine more if you turn an ear towards that area. If you can verify that's the sound, your dealer can exchange it for you under warranty. The fuel pump is in the fuel tank directly behind the seats, under the luggage racks. I especially hear my fuel pump when I start the car up and it's cold.

The rear differential can make noise when you're going slowly in first gear. However, I wouldn't expect you'd hear any sound from it on the highway at 70mph.