CLUNKING NOISE FROM REAR AXLE
Problem I found: Clunk when driving over even small bumps.
If Grand Cherokee is 1999-2004, then check this: Above the differential is a wishbone cross member control arm. The cross member attaches to the frame in front of the rear axle (bolts through rubber bushings), and directly above the differential, at the apex of the cross member, is a ball joint. The ball joint assembly is a flange bolted atop the differential, with three bolts, and the ball joint pin protrudes from the flange through the cross member apex, with a nut atop the pin. Raise the frame slightly, and with a pry bar, pry above the flange, and below the cross member, very near the ball joint. If any motion is detected, then the ball joint is worn from the ball joint socket, or the nut is loose on the ball joint pin. If the nut is tight, then replace the ball joint. 2000 GC part number is 52088808AB, and is available from online sources or dealers. To replace this part, you'll probably need to remove the cross member, as the ball joint pin through the cross member is in a tight location, is tightly wedged into the cross member, and requires a special v-shaped puller to remove the pin from the cross member. If you don't have access to the puller tool, then remove the cross member for this operation. Raise vehicle slightly, under frame, in front of rear wheels. Unbolt the brake line and brake cable retainers from the cross member, then unbolt the flange from atop the differential. Then remove the two frame bolts and manipulate the cross member out of the vehicle, from above the differential.
With the cross member before you, support on blocks, loosen the ball joint nut somewhat, or remove it, and with a beater protective block, sledge out the pin from the cross member. Inspect the rubber bushings at this time. These bushings require an arbor press to remove/install, and the arbor press to install requires a spider so as to not rip the rubber bushing from either the bushing shell or center spool. The press spider is a 4-point tool you can make up from a piece of aluminum.
Bolt the new ball joint flange atop the differential, using blue thread locker, and torque the bolts to 100 ft-lb, cheater pipe useful here.
Replace the cross member to the frame, and install the two frame bolts, finger tight. Pull the member apex down onto the ball joint pin, and run the nut down. Using a box end wrench, hold the pin from rotation while tightening down the nut. Torque the nut to 100 ft-lb. Tighten the frame attachment bolts to 100 ft-lb, and reinstall the brake cable and brake line retainers. Do not over tighten these retainer bolts, as they are passing only through the sheet steel side of the cross member. Take care to not strip the sheet metal threadings. Lower vehicle and remove jack.