1998 Jeep Grand Cherokee Axel

I am working on my daughter's 1998 Jeep Grand Cherokee. The rear end was making a growling noise, it has been pulled apart and bearings and clutch pack in the diff has been replaced. I am in the process on cleaning the axel tubes can I can put it back together again and have noticed a small round metal piece in the top of the tube about 3/4 of the way down on the top of the lt tube. I have been told there isn't supposed to be anything in the tube. Someone else told me it could be a vent. it's a Dana 44 HD, any help would be greatly appreciated

It's a vent....there is usually a hose attached to it on the outside so that water won't get in

I second Intrepidxj.. tis a vent.. if there isn't a hose attached to it.. get one attached to it and route it up as high as you can so you don't suck water into the axle :)

What was the condition of the gear lube when you drained it? Was it clear or milky white? Was there any metal filings in the bottom of the case?

Like everyone said, it's a vent tube. There should be a rubber hose that was connected to it and should be run up towards the floor of the ZJ. It will have a plastic valve at the end. If there is no rubber tube attached to it, it is possible water can get in there and become a problem. Easy fix, just grab the correct diameter tube and extend it up and away.