Loud tires or wheel bearings, help me diagnose please

[LDMF]

I just picked up my 300zx tt a couple of days ago. One owner, with records, 104k. She drove it only ~100 miles in the last 6 years. It sat on a battery tender in a heated garage. It runs well, passed PA state inspection and emissions, after a new brake master cylinder and fluid replacement.

Now here is what is bothering me. It is loud inside the car. Like a very low bass humming noise. I does get louder as you go faster. She seemed a little squirrelly on the highway, twitchy? My initial thoughts is that I need new tires. It is a shame becuse they are in excellent shape. Potenzas with ~11/32nds. It does not vibrate,wiggle or pull.

So my thoughts are that the tires have flat spots and/or lost their soft rubberiness. Or maybe a wheel bearing is making the noise.

Any thoughts or suggestion would be appreciated.

LDMF

[LDMF]

As I have done a little research on this site, maybe I have a driveshaft problem. The center bearing is bad or the bolts are loose on the differential.

[Rubyz32]

Does sound like the carrier bearing on the driveshaft. Go with a 1-piece from z1 or similar if you got the duckets. Otherwise however, if those tires are 6 years old, you might consider replacement. They may have low mileage, but they are old and that's all that keeps you and your baby from possible demise.

[DCaff300ZX]

+1 to everything Rubyz32 says, although I personally agree with my Z guy's argument that the OEM setup in new condition will last at least another 20+ years and is better than a 1 piece for vibration, as that is why it was designed that way. Most 1-pieces are designed for less weight and twist resistance and not to be as quiet as OEM, and you mention the noise as an issue for you.
I have stayed OEM with both of my Z's and have had no reason to regret it.

[LDMF]

My first stop was to have the tires checked and balanced if they were good. The shop did this and then told me that my 300zx needed front tension rods and the rear sway bar end links were broken. The front end parts could explain the squirreliness and the rear could explain the low pitch noise. But I still think it has a rotational problem. These problems would not be speed related to the noise. Could the mechanic be right?. I'm not thinking that it doesn't need these things fixed but rather he is not addressing the symptoms. Thoughts?

[DCaff300ZX]

I think your mechanic not incorrectly has started with the obvious problems, and would look for more once the obvious issues were gone. I agree that most likely either the carrier bearing is going bad (common) or maybe a u-joint, just not bad enough for a casual inspection. But it never hurts to go about things carefully and not jump to conclusions from people like us who can not see or drive your car.