350z whine at highway speeds that goes away after a minute

prizrak

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Making this it's own thread it started in the RT: AE thread but now that I have more updates I thought it would make sense to create it's own thread
To recap, once is started being cold the car started making a strange noise that goes on for a few minutes and then completely goes away. It never happens on the streets only highway so speed is a likely factor, it doesn't always happen right away, I could be traveling for 2-3 minutes at the same speed before it happens or it might happen almost immediately upon accelerating. It doesn't seem to be linked to acceleration as steady speed driving also triggers it. There is nothing about the car that feels off, it doesn't feel low on power, steering doesn't feel sluggish, etc...

There is a post with a recording of it here and the actual link to the recording itself is here

New info:
This happened again, the lights were off, turning A/C on/off did nothing, happens both on and off the throttle and seemingly in any gear (I tested 4,5 and 6) and at any engine revs, disengaging the clutch doesn't make a difference at all, neither is revving the engine with the clutch disengaged. Interestingly putting the car in neutral does make the noise go away, which makes no sense since there should be no functional difference between neutral and disengaged clutch.
 
In neutral, the input shaft isn't spinning, whereas even with the clutch in, it is.

Sounding like a variant of Nissan cold gearbox whine, even though the recording doesn't sound like it. Could just be the recording is crap.

If it isn't CGW, then it's a bearing going out in the gearbox. You've eliminated the rear output shaft bearing, though.
 
Thanks man, the recording is indeed terrible between the handheld iPhone, the wind noise and the road noise... At least this somewhat narrows it down, how big of a pain would a gearbox bearing be to swap out?
 
Thanks man, the recording is indeed terrible between the handheld iPhone, the wind noise and the road noise... At least this somewhat narrows it down, how big of a pain would a gearbox bearing be to swap out?

1. Remove gearbox from car.
2. Dismantle gearbox.
3. Since you basically are already there, rebuild gearbox with new bearings, synchros and seals.

You get the idea. Try changing fluids first. Remember, no GL-5 except the special ones specifically compatible with Nissan gearboxes.
 
So basically it's a full tranny (giggity) rebuild... Yeah fluids will be my first stop.
 
Bump, finally getting around to doing the MTF (since I decided to keep it after all), I've also decided to do the diff oil while I'm at it so went to the local dealership and while the MTF fluid is Nissan branded the diff oil they gave me is just Pennzoil GL-5, not being very familiar with the brand would it be fine or should I get something nicer (like Royal Purple or Redline) and return this (wife was picking it up for me, so I wasn't there to ask them wtf?).
 
Nissan manual transmissions take GL-4, but the diffs take GL-5. I would get something that's not Pennzoil. Mobil 1 is a commonly available better option. Don't forget the limited slip additive if the car calls for it.
 
Thanks! I'm actually not sure if it calls for the LSD additive, it does have a vLSD. For some reason finding info on the diff oil for my car is difficult, tons of info on MTF though.

EDIT: Can't seem to find Mobil1 in 80w-90 that my car calls for, any other brands to check out? The local vatozone has: Valvoline, Lucas, Coastal and Castrol

EDIT1: Actually found that I don't need LSD additive because the viscous coupling is aparently a sealed unit and there is obviously nothing that would need to be lubricated like clutches.
 
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Valvoline would be my pick for the stuff at Vatozone, but I know M1 is available in the more common 75W90 which while not *quite* the right spec for your car will actually work well for it with no problems. In fact, the slightly lighter oil is often thought to be an advantage for winter operations.

I'd point out that a lot of dealers put in 75W90 in Nissans that spec 80W90 with no problems... but we already know that dealerships will put GL5 into gearboxes demanding GL4 with disastrous results, soooooo.....

The only LSDs that need the additive are clutch-types. Gear only, viscous and the rest don't.
 
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Thanks I'll grab me some Valvoline then and return failzoil back to whence it came. I'll go with the 80w90 spec just to be on the safer side :) And yeah 75w90 is what's around in vatozone.
 
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