Whining Noise Coming From Rear End

How do I determine what is causing the whining noise coming from the rear end of my truck. I see seepage around the rear axle housing seal, but nothing on the ground.

Take the plug out of the differential cover and stick your finger in the hole to see how much fluid is in it. If your finger comes out with no fluid on it the fluid is low. And if it gets too low, the differential will start whining.

Tester

There are two plugs. DO NOT remove the lower one or all the oil will drain out. Check the level at the upper plug. The oil should be up to the bottom of the hole.

If it needs fluid - how do I refill it and what do I use?

What year is the vehicle?

Tester

2001 1500 2WD - 5.2L

The differential uses 80W-90 gear oil. You can get this at any auto parts store in quart plastic bottles. Fill the differential at the same hole you checked the level at using the plastic quart bottle by squeezing it. Fill until the fluid runs out the hole. And get an extra bottle. Because until that axle seal leak is fixed, you’re going need to keep adding fluid.

Tester

To replace the seal do I remove the cover from the housing, scrape it and clean it, remove what’s left of the old seal and replace it - like a gasket?

Yes. If it’s leaking at the differential cover gasket. If it’s leaking at the seal where the driveshaft connects to yoke going into the differential, that’s going to be a little more involved.

Tester

Thanks so much for your advice - I’ll start with the fluid level and go from there. Have a great night

Continuation from last night - anybody on line who can continue this with me?