My 83 zx 2+2 manual makes a strange whining-type noise coming from the rear at 45-47 mph only. The car only as 45K on it. Any ideas what could be doing it. Wouldn't be such a pain, but a lot of the cruising I do is in that range on back roads. Thanks.

 

Rear diff

 

Would a rear differential only make noise at one speed range..45-47mph? Car has 45K on it.

 

There are only so many things... what have you checked? Wheel bearings? Axle u-joints & boots? Diff mount / bushing? Driveshaft? Tires? Check them........

 

Could be a number of things...

- Rattling Catalytic converter - When these go bad or get loose or whatever it is, they will have a resonant buzzing sound that only occurs at very specific rpm/speeds

- Rearend - gear noise/humming. Most likely IMO. Change your gear fluid and see if that helps. You might be a bit low after all these years, or the goo is spent.

- Wheel bearing - maybe but I'd try changing the gear oil before anything else.