2004 Discovery II SE 155,000 miles
Started as a high pitched whine only during acceleration. Read thru the forum to give me ideas and steps on where I should start looking. Removed front driveshaft and inspected, nothing detected under visual inspection. It’s been upgraded and has the zerk fitting. Made sure I locked the front differential and drove around the block. Still makes noise. Next I drained fluid from front differential inspected fluid. It was dirty and black. But no signs of shavings or milky. Refilled with synthetic. Drove for a bit still makes noise. Now I’m thinking it might be the wheel bearing. It’s starting to stick and smooth grind in forward and reverse. My question is how do I diagnose between the diff and the bearings? Could it be something else upfront that I am missing. Deciding between a front differential rebuild kit or new bearings. Where else should I inspect before making buying either.

 

Jack it up and check for unusually side to side play in wheel bearing.

 

Did you check the transfer case fluid? Might want to drop the transfer case lower cover.

 

second the t-case fluid check - lost my t-case on D1 - the breather hose dropped on to the exhaust manifold and it melted shut - caused the fluid to blow out thru the case from pressure (but no drips on drive) for me to notice - it grinded for a few miles then self destructed - but you do have to check the front drive line and brakes to rule those out

 

I’ll do that on my day off.

 

I did, looked fine. Plus the noise is definitely coming from the front. It’s either the front diff or bearings. Just not sure how to isolate either of them from one another to test.

 

Break it down and remove the bearings rotate them by hand, should be easy to tell if they are bad enough to grind you will feel it

 

so I got all four wheels off the ground today. Wanted to check the bearings and also get a better inspection of things in motion. Wholly smokes I was wrong. The sound is definitely coming from the transfer case. Also all four wheels move when in drive except for the rear passenger. It either moves slowly, or not at all. Interesting thing is I can make it go I reverse of all the other wheels. Might be a different problem might be the same. My next step is to remove the remove the rear driveshaft and see if the grind goes away.

 

brake caliper on rear pass

 

Had similar symptoms. The front diff blew out weeks later. Changing it is super easy if you end up needing to replace it.