2001 Jeep Wrangler Rear noise at first gear low speed

Have you had your rear disk brakes checked recently?

Make sure the U joints on the drive shaft are well lubricated.

If you would like to better identify the problem raise the vehicle and securely rest the rear axle on two jackstands with a 1/2 ton floor jack resting under the differential. Place blocks behind the front wheels and ensure that the vehicle is in 2 wheel drive. Start the vehicle and place it in drive and start listening for the location of your abnormal noise.