Rear differential whine (-_-)

Did a search all the way back to mar09 ... nothing.

She's 1990, and a former auto-Xer from WA. She whines on the freeway on deceleration. As soon you put a little bit of load/ gas on it, it goes away. At first we thought it was a wheel bearing, we do those, and its still there. A mechanic drove it around and said, "yup, its the diff." However, he was busy and didn't go into too much detail on the exact problem. (Of course, it was a free inspection).

Has anyone else ever had the whine? Is this a small or big job? What are the possible problems, and will I need to search the ends of the earth to find a rear diff if its blown?

Thanks guys.

tried to make the cruise control work next thing you know a loud whine started on the highway from my diff and 2 days later my tranny blew with my diff. i hope this wont happen to you lol, open your diff and look if the teeth are in good condition, maybe you just need to add oil, put 75w-90 gl5

I think we lost some archived threads from a while back....I had this exact thing a few years ago and posted a similar thread about it. I never found out quite what caused it. It started after I changed the diff fluid (probably hadn't been changed since 93') and changed to a solid rear diff mount. It lessened over time so I never looked into it more. Never had any problems other than the noise. Might have been the solid diff mount making it transmit more noise? :shrug: