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I can't imagine how you could hear a hissing at those speeds 5th gear redline is pretty fast. It could be tire feathering, very common issue.

 

I thought the speed limiter kicks in before you can redline 5th.

 

I want to hear Samuel L Jackson shout : get these snakes outta my 350z

 

Maybe it was wind noise from the window not sealing tightly. Since it didn't start until you were well over 100mph, I wouldn't worry about it.

 

If you have a 03 with 17k miles,I'm thinking the previous owner has the
original Bridgestones on the car.Its also quite possible the front tire feathering
issue was never fixed or,fixed correctly.I'm guessing its coming from the inside
section of a tire.However,most feathering noise happens at lower speeds
especially when you are slowing down and braking.It also can be a air leak
around the windows,doors etc.The Z is not made to the standards of say
a Merc.Its a sportscar sold at a very competitive price.Its not a silent cabin
by any means.

 

I'd be wary of driving over 100mph on tires that are ten years old, regardless of their apparent condition.

 

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