leaving it in 5th seems to solve the problem.. but anyone knows the reason why? i wasn't lugging the engine at all in 6th.. it's quite strange that it would whine like that .. the sound seems to be coming from rear of the car, which is even more puzzling :confused:

don't know but your 370z should run fine at 45 mph in 6th gear.
my 2.5 liter beetle is a lot weaker and even it runs fine at 40 mph in 5th gear.

i think the recommendation of driving in 5th gear at 45 mph is for 4-cylinder cars with 1.5 liter engine, not for 6-cylinder cars with 3.7 liter or larger engine.

lol i think my 2 liter s2000 did fine in 6th going 45mph too.. w/o any weird noise.. i guess the z just has one noisy tranny..

Too long of a gear ratio with not enough power...All cars are different, especially when they are different makes and models. Gear ratio, weight, differential, low end, high end, tuning, clutch, TIRES...everything makes all those cars run differently. s2k for example is VERY light making very good power vs wieght making them a good adversary on the track, I just don't like convertables...sorry.

As for the noise, thats just how this transmission/drivetrian is. If you let it idle you can here chatter coming from the tranny. you could try using readline tranny fluid and that should help it run quieter:

Redline MT-90 1 qt (manual transmission fluid)

you can also try to change out the diff fluid also.

You're just driving the car inappropriately. There is no benefit to driving in 6th gear at 45mph. You'll actually get worse gas mileage if you even slightly accelerate in that scenario. Much better to just be in 4th or 5th without the engine laboring. The Z is happiest from 2500rpm on up, and I aim to be at least over 2k rpm when driving around.

:iagree:

i would agree if the 370z with AT would drive at 2500 rpm when cruising around town but I don't think so. All the AT cars I have ever driven all drive at around 1,500 rpm when cruising around town. Like i said, page 5-19 of the 370z owner's manual said for normal acceleration, change to 6th gear at 33 mph. For quick acceleration, change to 6th gear at 50 mph.

imo, driving at 2,500 rpm or driving at 1,500 rpm are both OK. It depends on which rpm the driver wants the engine to operate at and that's why we bought a manual transmission so we can make that decision instead of the computer making that decision for us.

In the 370Z you'll actually wanna use red line mt 85