Transfer case

I have a 2000 Grand Cherokee Limited and have had no issues with it until 3 days ago. We were driving on the highway and heard a thumping noise, almost as if it were the road, it happened a few more times and we decided to turn around and come home. It sounds like it is coming from the drivers side front tire area. At first thought I blew a shock, I have 100,000 miles on the car and am willing to bet they are original, I have put a little over 50,000 on myself. I feel a vibration in the steering and a thumping sound when I am accelerating over 70 mph when you let off the gas it goes away. I took the service manager for a drive from the local dealer who had never heard such a sound. He originally thought it was an issue with the brake pads or tires, they called today and gave me 'there is an internal problem in the transfer case, it is too dangerous to drive and the part will cost 2900 and be here tomorrow' I am a chick but have been around cars long enough to buy that. Anyone out there have any suggestions. I am going to have someone follow me down the road to see if the tire has a hop to it and replace shocks if I need to but can't imagine it is the transfer case.

did they check the frt driveshaft?

Do the 00s have CV axles? You may want to peek under and look to see if there is black grease anywhere around the CV boots. I agree about getting the driveshaft looked at. It sounds similar to when mine went out in my Bronco.
Byronp

I picked up the car and found the noise had changed, took it down a dirt road and tested the transfer case noise in 4 LO, got home and checked the driveshaft which has no play and found that when you make the transfer case spin while in park in the driveway there was clanking and a lot of noise, a new transfer case it is. There is a lot of slop and play - much more than normal. So thanks for the help but unfortunately it needs a new transfer case. Hopefully I can find a rebuild for less than 2900, which is what Jeep wants.

Vehicle noise: Popping/snapping noises are usually corrected by replacing the front driveshaft. In many cases, that unit probably has a dry universal joint.