How to Check Differential Fluid Levels

Keeping the fluids in your vehicle’s differential, especially in 4-wheel drives, is very important to the life of the ring and pinion set inside. If your vehicle is just factory stock, 90 weight gear oil is almost always sufficient, but check with the manufacturer’s recommendations just in case. If the vehicle contains a locker or limited slip differential, there are sometimes special fluids required for best performance, so always do a bit of research to make sure you put the correct fluid in.

Things You'll Need

• Crescent or allen wrench
• Gear oil

Instructions

1. Locate the differential housing. It is the lump on the axle in between the two tires, known as the "pumpkin." If your vehicle has a differential cover, it will have a fill hole.

2. Locate the fill hole. On some models, it will be a square nut head sticking about 1/2 inch out of the cover itself, and on other models it will be an allen-style nut, recessed inside the cover.

3. Remove this plug, either using a crescent wrench or allen key, whichever your application requires.

4. Put your finger in the hole and feel for fluid. If filled correctly, the fluid should be almost to the bottom of the fill hole when on level ground. If you have to reach very far in, add some more.

5. Reinstall fill plug, but don't over tighten. They are designed with a lot of threads so the fluid won't leak, so there is no need to muscle these on. Just make it nice and snug.

Tips & Warnings

• If the fluid appears milky, it has probably mixed with water and should be changed entirely.

• Don't forget to reinstall the drain plug!