Given the dynamics of what the driveshaft is actually doing -- spinning at thousands of RPM at highway speeds for instance -- if a joint was loose you'd be getting many more symptoms than just a clunk when you "punch it." Certainly check it: jack the car up and support it with stands under the axle tubes to maintain the normal driveline angle, then crawl under it and wiggle and tug on the driveshaft for all you're worth. I suspect you won't find anything loose in the shaft's U-joints.
Assuming the joints are okay, there's three things that come to mind that you should check:
1) Check the upper torque boxes (the sheetmetal mounting points for the upper control arms) to make sure they are still securely fastened to the floor and frame rails. I've heard stories of these being torn away in high-power or high-traction cars. Easy to check while you're under mucking about with the driveshaft.
2) The upper control arm bushings. Tough to inspect when installed in the car but any noise related to "punching it" -- which imparts a significant reaction torque moment to the axle housing which is supposed to be controlled by the upper arms and the torque boxes -- would make me suspect the mounts or bushings.
3) Lower control arm front bushings. Because of the geometry of the 4-link rear suspension, Ford had to make these bushings very pliant to prevent binding. They're so pliant, in fact, and give so much that Ford needed to had separate shock absorbers (the quad shocks) to help control axle fore/aft movement. If these bushings break or get even softer, the rear will make noise.
Assuming the joints are okay, there's three things that come to mind that you should check:
1) Check the upper torque boxes (the sheetmetal mounting points for the upper control arms) to make sure they are still securely fastened to the floor and frame rails. I've heard stories of these being torn away in high-power or high-traction cars. Easy to check while you're under mucking about with the driveshaft.
2) The upper control arm bushings. Tough to inspect when installed in the car but any noise related to "punching it" -- which imparts a significant reaction torque moment to the axle housing which is supposed to be controlled by the upper arms and the torque boxes -- would make me suspect the mounts or bushings.
3) Lower control arm front bushings. Because of the geometry of the 4-link rear suspension, Ford had to make these bushings very pliant to prevent binding. They're so pliant, in fact, and give so much that Ford needed to had separate shock absorbers (the quad shocks) to help control axle fore/aft movement. If these bushings break or get even softer, the rear will make noise.
I agree. I had an 01 with the same problem but sold it before i fixed it. I would also check the suspension, too much spring travel can be causing the U-joints to bind.
My car would only make the noise when suspension travel was at its greatest. Hard acceleration can cause the nose to come up high, increasing U-joint angles too much.
Also check the slip joint.