I have a 98 TJ that I bought in July it has 156480 miles on it and a 4.0 that runs like a top. But it seems to have a noise coming from the rear axle at hi-way speeds. I have checked the differential gear oil and it is at the correct level but it is almost clear and seems very thin. I jacked it up and with it on jack stands and in drive and you can hear the noise so I know it is not coming from the tires. Everything on the Jeep is OEM as far as I know. I donít plan to do a lot of heavy wheeling mostly back roads and trails in the Upstate of SC. So what weight gear oil and what brand is best or at least very good? And any ideas about the noise and how much noise should I expect and what are some of the possible causes?