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

[Silvestris]

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.

 

[Silvestris]

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?

 

[2vNotch]

clunk lol

 

[CQD24]

Have the same problem. Driving me crazy.

 

[demented22]

my f150 did the same thing. two days later my carrier split in half. it has an 8.8 in it also. heavy truck, 35" mud tires plus some nasty burnouts = alot of money haha.

 

[Silvestris]

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.

 

[2vNotch]

My buddy went round and round with this issue on his 97 cobra....came down to a bent axle that had chewed up the bearing AND u joints

 

[Silvestris]

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.

 

[2vNotch]

Im sure it would....hes got a 96 mystic that he bought with 60k miles in 2002, to this day it has 71k miles so he wouldnt have noticed it vibrating lol its a garage queen! The story was he slung it sideways and waxed a curb breaking the axle smooth off and ford replaced it and the suspension/brake pieces on that one side, never even checked the other side, so he kept hearing this clunking just moving it in and out of the garage so we tore it apart one day and sure enough....

 

[Silvestris]

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.

 

[bhuff30]

Whatever the problem is, you obviously need to stop driving the car and tear the rear end apart. It is likely you will find a bad bearing, but as others have noted, there are a host of other possibilities. The sooner you address the issue, the less money it will cost you. Keep driving, and you are guaranteed to replace the gears, all the bearings, and maybe even the differential.

Yes, the 8.8 is a strong rear end, but that doesn't mean it never has problems. The pinion bearing on my 97 GT went bad, and it never saw more than the stock 215ish horsepower. The pinion seal on my dads 06 GT took a dump (8.8 as well). And of course, bad rear wheel bearings/seals are common.

 

[trinity_gt]

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.

 

[Silvestris]

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.

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.

 

[trinity_gt]

If you can move the control arm by hand I think you've found the source of the noise.

But go check it again. It's possible the bushings are bad but you should double check to make sure the upper control arm brackets that mount to the floor/frame of the body have not been damaged. The bracket's I'm referring to can be seen here:

Check this article:

http://www.popularhotrodding.com/tech/0911phr_1993_ford_mustang_notchback/index.html

 

[demented22]

i agree that i would inspect the control arm mounts, esp if you can rotate the one. trust me, my 8.8 in my truck was beyond abused haha.

 

[Silvestris]

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.