Where is that noise coming from?

Sorry about the length, just want to give enough info. 2000xj, 61,000 miles, I6, automatic, 8.25 rear. 30" tires. Added a 2" RE lift about 5 months ago (spacer up front full all in rear), and 1" transfer case drop. Jeep has given me about 15,000 trouble free miles with this set up. I was pulling my trailer home the other day (small, about 1700lbs) and felt what I thought was the transmission slip off and on for about 2 hours. Also felt much more vibration than ever before. Sounded like a droning noise around 70mph along with the vibration. Also heard a high pitch whine from somewhere underneath at certain throttle settings. Shop back home found nothing wrong with the transmission and had them change the fluid and filter. Today I started noticing a popping noise from the rear while going around a corner, as well as what felt like a transmission slip again. It also feels as if there is more vibration after 50mph associated with a generally unstable feel to the ride. If I do sharp turns I can hear the popping noise, but I can feel it under my left foot, which is sitting on top of the transfer case. I took it to the guy that did my lift and he could find nothing wrong externally, but he said it sounded like the limited slip in the rear end. I don't have a limited slip and I am out of clues. I am assuming all the symptoms I described are related since they all started at the same time. Any insight would be greatly appreciated.

Thanks

I bet you have a Trac Loc limit slip in the rear diff.... If this is the case, then you need to change the diff fluid, and add the correct amount of limit slip fluid. What you are hearing/feeling is the chatter of the clutch plates on the limit slip because they are not longer slipping....

Ivan

How do I know if I have Trac Loc? If I remember right I had the jeep jacked up in the rear and spun one tire and the other spun the opposite direction. Isn't that just the regular open diff?

Thanks

There are a couple of sure fire ways of determining if you have a Trac Loc or not. One would be to take the VIN number to the dealer and have them run a build sheet to find out how it came from the factory. Another way is to check the passenger side axle tube near the brake backing plate. There should be a bar code sticker with "Trac Loc" written on it, if it has one.

The jacking up and tire spinning thing isn't always a reliable way to determine if you have a Trac Loc or not. But with your rig being a new and with relatively few miles on it, it may work.

Ivan

Thanks, I'll have to go look for that.

Agree with Ivan! That noise in sharp turns is sure a limited slip dif. noise.
When was the last time you change diff. oil? Once, my service changed oil and have to came back with that noise; the man heard it and said "oh I know what it is...came back with a MOPAR aditive as they forgot to put special slip Diff. oil on it.
Keep telling to know end of the story.
Good luck.

Thanks for the info guys. I checked the rear and found the plate. It said 8.25 open. So I guess no limited slip. I did just check both the rear diff fluid and the transfer case fluid. Both were very dark with the transfer case fluid on the black side. Does this mean the transfer case is ruined? I know dark fuid in a tranny is no good. Since I am off today it looks like I will be changing some fluids out.

Ryan