The unanimously hated "clunk" sound... I got it...

Here's the story. Drove from my bus stop to work without noticing a thing. Normally the radio is blaring so I can hear it over the engine though. Go to work, get off, start the car, put it in reverse, let out the clutch, and I hear a clunk from the back. I'm angered at this. Put it in first, let the clutch out, another clunk. About now I'm thinking my U-joints are going bad. I start driving and testing the situation out. Shift to 2nd, nothing. 3rd, nothing. I let off the gas and engine brake, clunk. Accelerate from slowing down, another clunk. Now I normally have a soft growl coming from the back of my car. I thought either the ring an pinion clearances are off or a bearing is bad, but it never gave me trouble and never noticed metal fragments in the gear oil so I put it off. Now it sounds a bit different. Lower tone, but quieter. Could be my mind playing tricks on me, but maybe not. Here's the kicker. I pull into a parking lot and make a rather sharp turn. Clunk. Now I'm confused. I park, put the E-brake on, put it in first and let the clutch out. Nothing. Did the same for reverse and had the same result. Now I'm thinking one of my dry rotted to hell bushings let go on a control arm or something. Later that night I leave, clunk here, clunk there, pull up in my buddies rough gravel driveway and I'm getting a few clunks here and there further supporting my failed bushing theory. I get out, try pushing the rear end around with no result. Later I leave my buddies house to come home, more rough road, more clunks, and then I had an idea. Lets see if it clunks both on the throttle and coasting in neutral while turning. I'm going down a flat straight smooth road in 3rd, shake the car back and forth, nothing. Then I pop it out of gear and coast, shake it back and forth, and it clunks. This gets me to thinking something in the rear end is messed up. Now I'm home, posting this thread, confused and hoping my rear end doesn't blow up. It's the only car I have and I won't be able to get it in the air till tomorrow afternoon. You guys have any ideas? These mysterious sounds are the worst to diagnose and they scare the poo outta me.

Update:
I started the stang up this morning, let it idle a bit, ABS light is on. Drove it a little, still clunking, light went off for a bit, then came back on. Made a stop at a gas station, turned the car off. I came back, ABS light is off, no more clunking. Went to my bus stop to Lincoln Tech, came back started my car up, no ABS light, and still no clunking noise. This little problem is really starting to confuse me. Ideas?

That makes me feel safe lol. I haven't abused the car much. I've only done one burnout. I've floored it plenty of times but it's not even hitting 300hp. The 8.8 should hold fine. Should... I looked underneath it just now and noticed a couple small things. The top left control arm that attaches the differential housing to the body seemed a little more loose than the others. All of anything back there that is bolted in I tried to move, and all of them were nice and tight beside that one control arm. I could twist it a little bit. I've also noticed all the play in the driveline. Most of it is form the U-joints, both of them seem to have the same amount of slack. I've took pictures trying to explain how much slack I'm seeing. I put the trans in 1st, moved the tire as far back as I could without engaging the limited slip, and then turned the wheel forward as far as it would go. I'm not familiar with how much slack would be acceptable. After I put the car back on the ground I hopped in, put it in 1st and let the clutch out. nothing. Same for reverse. I'll have to raise the back end again when and if it acts up again.

Wouldn't a bent axle cause a lot of vibration? I drive a lot on highway and haven't noticed any vibration. On a positive note, she drove just fine today and I picked up a keyless entry module and driver side door hinges from the junk yard. I guess I'll have to start saving for a rear end rebuild kit. I'm planning to rebuild the trans and engine anyway.

That sucks. I've always heard the 8.8 was a tough axle, especially on the Jeep forums. I remember one time I pulled into a parking lot full of snow, tried to turn and just went straight. Nailed a curb on the left front rim at at least 15-20mph. Never saw anything bent, still drives straight as an arrow. I guess that's why the thing weighs roughly 2 1/4 tons. Everything is giant chunks of hardened steel.

trinity_gt said:

The 8.8 is plenty strong. It's under the GT500 so Ford thinks it's stout enough...

As for the clunk, you might want to turn your attention away from the rear axle and toward the upper control arm mounts on the chassis. It's not that uncommon for the brackets to tear and pull away from the floor especially if the car's been abused (e.g. drag raced with slicks on a prepped surface) or if it's seen a lot of winter miles in areas where road-salt is common. Since these mounts serve to locate the rear side to side and to deal with axle wind-up clunking and knocking may be heard in both turns and when transitioning from coast to drive if one or both of these mounts is damaged.

Click to expand...

Awesome! I noticed my left upper control arm was a bit loose, enough for me to rotate a bit. And when I did the lowering springs and dropped the axle down, I noticed all my bushings are shot. I'm in north west Indiana so we get a lot of snow and road salt. That helps ease my mind a bit because control arms are a lot easier to replace than rear end internals, and you can limp the car home a lot easier if a control arm goes out compared to the whole rear end. I remember I had to drive my old Lumina a good 10-20 miles with the rod going out because the intake gasket sprung a coolant leak. I never want that feeling again lol.

Yeah, I'll have to get it up next weekend and look. I wish I had a lift. Right now I have my hands full with a parasitic draw problem.