Just got back from having my FD installed, and I had a question. At around 3k on the tach if I depress the gas pedal just enough to maintain speed I hear a droning noise, if I depress the gas a little bit more (to where I am accelerating) it goes away, as does it if I let off the gas a little bit. My installed (Street Image) said that they didn't hear anything. So I'm wondering, does this go away after a little while, is this normal, or do I have to go complain to somebody?

 

I have heard of some droning in aftermarket gears to be honest... I don't think it is that big of a problem as long as the people who installed them are trust worthy, and told you everything was installed correctly.

 

I just got my 350evo gears installed too. I haven't really had an opportunity to go out and drive the car much until this weekend. I noticed something very similar to what you are decribing except that I would probably call it a slight whine. I thought at first that what I was hearing was my flywheel since I have the Nismo flywheel and I hear it sometimes when the rpms lag below 2200 rpms and I accelerate.

Like yours the sound goes away when I accelerate. I notice it more in 5th gear than the other gears. The guys who did my install have done several others and they told me mine went in fine. I have a friend who has the 3.9 FD and I didn't notice the sound in his car. I am going to ask him about it as soon as I can. I don't know if it is normal either, but it may be.

 

Honstly... seems like they didnt set the backlash correctly on the gear..

 

Well, I'll wait to see what other people say then I suppose I'll give the shop a call to see what they say.

 

Its the backlash setting.

 

BJ,

Does what I am describing above sound like there is an issue with mine too?

 

BJ,

Thanks for the info. Besides being annoying, I'm assuming that overtime this will be harmful?

 

Any word on the solution to the noise problems with the 3.9 for any of you guys? I have the same issue with my install, especially when I am in 5th gear. Any updates or feedback would be helpful.

 

I just got my car back today and after a long discussion with my installer (Street Image) the issue is still there. The tech told me that the gears are meshing dead center, but there could be other issues. One thing that he said was that when my car was on the lift, they went through the gears and at higher speeds the car started shaking the lift, so my tires are likely out of balance. So he thought we should start by getting that fixed and see if that is causing the harmonic. After that if the problem still existed, he said he could push the gear more into the pinion offering less travel (I'm paraphrasing since I don't know all the technical terms), and also trying a diffrent fluid to see if that calms things down. Since it doesn't happen under load and the gears are meshing properly he says that it isn't wearing the gears, but simply that it is annoying. I'm hoping that balancing my rear tires will help, but honestly I don't hold out much hope that it would solve the problem. We'll see.

BJ, does this sound plausibile?

 

Just got my rear tires balaned and the noise is still there (honestly, I'm not supprised). My installer was thinking about getting a thicker pinion nut to push the pinion in further. I ordered the additional pinion nut when I got my FD from Performance Nissan, is this the same thickness as stock, or is it thicker?

 

Yeah that doesn't surprise me either. My tires didn't go bad overnight once my gears were installed. I am taking my Z back today because the noise has gotten too annoying.

 

What kind of wheels do you have on your car... If they are aftermarket, do you have hub-rings on them?

There are many different parts you need when installing the final drive gears... Its not just a remove / re-install...

You will need:

New Pinoin Nut
Pinion Oil Seal
Front and Rear Pinion Bearings (I recomend replacing some people re-use good luck to them)
Spacer Crush Housing
Pinion Washer Adjust Spacer

Side Differential Bearings
Side Differential Seals
Side Differential Washer Adjust Spacer


There are 15 different Pinion Adjust Washer sizes
There are 13 different Differential Side Adjust Washer

They have to measure for each of these so they are within tollerance...

Too much of a gap will make for noise / too tight will make for more...

Basicly, you have to have the install done again...

I can recomend you to a really good rear end shop if you would like...

 

The installer is going to take another pass at it after he gets in some shims to help adjust things. I should be going up for them to try again soon, I'll post back with the results.

 

I took mine back to the shop and the result was this....

"Unit is breaking-in...Noise is dissapating...
This is normal...Needs more mileage to be perfect..."

I was under the impression that the gears did not need to be broken in, just the LSD? I suppose I will ride it out for a bit and see if the noise really just goes away? I am not aware of any really good rear end shop in the Vegas area. I will keep a look out for one to get a second opinion. rgreene, definitely keep us informed on your results. Thanks.

 

umm... thats a line...

 

i have the central 20 one. don know if this help but my installer recommended 400 mile to break in before driving it hard. he also said that gear noise is normal for the first hundreds miles.

 

I talked to my installer yesterday. I am going to take it back in next week for them to check the thing out, including the backlash setting. I am still hearing whining while maintaining a constant speed. They also told me that we may try a different brand lubricant or an additive. I'll keep you posted.

 

Anything further with this guys? I am really considering getting the final drive swap done, and I am a bit on the fence about it unless this is just an issue of breaking it in. Any further info would be great!

 

There is small whining takes place on many 3.9 FD's .. around 55-70 mph if my memory is correct. Perfectly normal, to my understanding .. I have it.