My 2003 G35 Sedan has increasing noise from the drivetrain.

it is noticeable around 40 mph and increases as speed increases.

the sound is more of a "whine" than anything else, similar to the engine rpms if highly revved, but the tach relates normal rpms. we have changed tires, put car on rack to see if running it created same noise (not), put car in neutral going down the road (no change in noise).

we went to infiniti dealer this week, they had two technicians look/drive it, and think it is transmission not shifting out of 3d - but the tach does not show high rpms....

HELP?

Is it coming from the rear? Maybe a rear diff issue??

We don't think so but as we can't hear noise unless on road, locating is always difficult.

Possible wheel bearing?

We put it on the rack to check all the wheels...turning them were fine.

How many miles? My money is on wheel bearings. I did both fronts before 100k miles due to whinning.

My transmission whines on cold drives until the fluids warm up. Just started doing it this year, never any issues before, but a common problem I have heard about. Have you changed the diff/trans fluid?

About 110,000 miles on drivetrain.

But warm or cold it still whines.

on my 2005 g35x i had a whine and it was the fuel delivery lines on the back of the engine, trying to remmeber the exact name of the parts that got changed...

fuel dampers or something like that...

Did you notice it at certain speeds or any speed? Mine is noticeably above 30mph.

it was above a certian speed... and only when i was on the accelerator. I dont remember the exact speed sorry.

I have a 2004 G35 which has a similar drive line noise between around 40 mph and 60 mph. Not noticeable below 40 or above 60, although I think it is there. Haven't been able to locate the problem. Noise doesn't change when I go around turns so I don't think it is a wheel bearing.