What is that high-pitched whine coming from my (car's) rear end?

Dear Car Talk

Dear Car Talk | Mar 01, 2000

Dear Tom and Ray:

I have a 1995 Ford Aerostar (extended version) with 85,000 miles. For about the
last 10,000 miles, I have been increasingly aware of a moderately high-pitched
whine that seems to be coming from the rear of the vehicle. This noise reminds me
of the "lonely highway singing" of big-rig tires on a clear night. My tires and
shocks are good. The noise starts at about 35 mph, and as the speed increases, so
does the pitch and volume of the whine. At highways speeds, when I take my foot
off the gas -- even slightly -- the noise seems to go away. When I put pressure
back on the gas pedal, the noise returns as loud as ever. What's the noise, and
how do I get rid of it? -- Mike

TOM: The noise is coming from your rear end -- if you'll pardon my saying so,

RAY: And the way you get rid of it is either by replacing the rear end (i.e.
differential), or by turning up the radio.

TOM: You've got classic differential whine. The good news is that, despite the
fact that it will get louder and louder, it'll probably keep working for years
without leaving you stranded.

RAY: The bad news is that it'll drive you legally insane long before then. Look
at my brother. He used to be normal, before his Suburban rear end started
whining. Now look at the poor guy!

TOM: The first thing you need to do is check the oil level in the differential.
If you're lucky, it'll be low and you can fill it up and at least hope to slow
down the rate of deterioration. And then you can try every bottled additive you
can find in the auto parts store -- especially the ones that say "Miracle" on

RAY: If the truck is in otherwise good shape and you decide to replace the rear
end, we recommend a used one from a junkyard. But be aware that it might be a
whiner, too.

TOM: Hey, that's what happened when I got remarried!

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