Whining noise at highway speed- Cause?
 

I am getting a high pitch whining noise that i notice around 60mph and it gets more noticeable at higher speeds. The pitch changes at speed, and when I lift the throttle, it disappears. I suspect it may be a rear end ring and pinion that has developed a wear pattern that makes noise with torque from throttle and disappears without the torque. Seems to make noise in 5th and 6th gears. Thoughts? Anyone else get this noise?

I had an 1st gen RX7 that made similar noise that was the ring and pinion wear, so that was where my speculation came from. Thanks

You can always start with a rear diff fluid flush and replacement. at 27k Miles when I did my AMSOIL everything, my rear diff fluid was black, black, black...

The Subaru transmission fluid looked healthly but I had 1st and 2nd gear notching issues that needed to be resolved with better fluid. That has since been resolved.

I've had that noise for the past 40K miles.
Here's the thread where other owners have experienced it: http://www.ft86club.com/forums/showt...h+pitch&page=3


For the duration that I've had it, it hasn't gotten louder. To me it doesn't seem mechanical but electrical in nature. Especially how sharp the border between the noise/ no-noise occurrence is. I mean you only barely touch the gas pedal to make it appear and then it doesn't chance the tone no matter how much load you put on the engine. Same with lifting the throttle - it's a sharp transition into no-noise when the foot is almost coming off the pedal.