A rear differential is also called the "rear end". The only worry for
the rear diff is scheduled replacement for its gear fluid. If you do not
know when the last time the fluid was changed, it doesn't hurt to change fluid
now. The rear diff contains the limited slip differential or LSD.
On a bad rear diff, you'll usually hear a lot of whining or grinding toward the
rear of the car. This noise gets louder as speed increases. It is
possible to rebuild these units, but it's easier (and cheaper) to swap in a good,
used rear diff.
For differential fluid (viscosity) recommendations, check your owners manual or
the Mazda FSM for more details. We highly recommend using synthetic gear
oil for your rear diff.
Click here for synthetic rear differential fluid recommendations!
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