Clanking Sound

[lukerbsn]

I have noticed a clanking sound in the rear of my 84. It has an 8.8 rear end and the gears inside are all good, no chips or anything. The rear end seems to be bolted on solid. The rear drums have a ton of play, they shift around a lot when the car is jacked up and if you wiggle the wheel. The clanking happens when I go over uneven surfaces like backing out of a driveway, whenever I take off from a start, or when I take off from reverse. If I shake the car or wheels you can also hear it. Has anyone had similar problems? And what was the issue?


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[liv2roc]

u-joints?

[lukerbsn]

u-joints?

While I was underneath the car I looked at them and didnt see anything concerning or out of place. They looked pretty clean, but I will double check tomorrow.


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[stangPlus2Birds]

The rear drums have a ton of play, they shift around a lot when the car is jacked up and if you wiggle the wheel.

I'm confused.
Do you mean the drums are moving when the are wheels bolted to the rear axle, and the drums pressed in between the rim and the axle?

When the rear wheels are bolted to the axle/car, the drums can only move as much as the axle.

Imho, take a video, use the best resolution (has the best audio), and upload to youtube.

If I shake the car or wheels you can also hear it.

You're lucky. Imho, try to get someone to listen while you shake the car.

It could be a ton of things.
Being more precise/accurate may help people help you.

Fwiw, on my Olds, I had some weird noise in the rear wheel. We knew it was in the rear wheel. We(the mechanic and I) could both get it to happen during a short drive.
As first, I tried throwing parts at it. That didn't work.

The mechanic ended up spend many hours on it, but he tracked it down.
I had a worn adjuster for my parking brakes. Over some bumps/etc, it would shift very slightly, and the backing plate, rotor, and tire acted as well-tuned amplifiers.

So, as I said, it could be a ton of things.
But, it's likely worn bushings/etc.



Good luck!

[lukerbsn]

I'm confused.
Do you mean the drums are moving when the are wheels bolted to the rear axle, and the drums pressed in between the rim and the axle?

When the rear wheels are bolted to the axle/car, the drums can only move as much as the axle.

Imho, take a video, use the best resolution (has the best audio), and upload to youtube.



You're lucky. Imho, try to get someone to listen while you shake the car.

It could be a ton of things.
Being more precise/accurate may help people help you.

Fwiw, on my Olds, I had some weird noise in the rear wheel. We knew it was in the rear wheel. We(the mechanic and I) could both get it to happen during a short drive.
As first, I tried throwing parts at it. That didn't work.

The mechanic ended up spend many hours on it, but he tracked it down.
I had a worn adjuster for my parking brakes. Over some bumps/etc, it would shift very slightly, and the backing plate, rotor, and tire acted as well-tuned amplifiers.

So, as I said, it could be a ton of things.
But, it's likely worn bushings/etc.



Good luck!

I believe it is the actual drum moving. Im not familiar with drum brakes and am learning as I go on so sorry I couldn’t be more specific. I will look deeper into it tomorrow and hopefully find something.


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[Tigger]

Maybe the backing plates are loose?

[WilliamCapri]

There is end to end freeplay between the axles and the diff. You can push the rear side to side and it will make a distinct clunk-clunk. That's normal.

[KevinK]

Could be the clutches in the rear. Did you add the friction modifier?

[erratic50]

When I was running my stang across the country back for long distances in the 90's I found it was imperative to get the gas tank as full as humanly possible. You can get about 2 1/2 gallons more fuel in a four eyed fox if you park it as just the right slope and your rock it when you're filling it. As you do that the ol 8.8 makes a distinct clunka-clunka. Its the axles rattling back and forth on the C clips in the rear-end. You may hear a little bit of a ooonk ooonk ooonk sound or a slight dragging sound as the pads slide back and forth on the drums and move around a little on the backer plates. Its caused by the drums and axles moving back and forth from side-to-side of the axles and drum vs the backer plates.

If you get under it and look as that side to side force is applied to the rear quarter of the car getting it rocking good, you should not see a TON of movement right there. You'll have some movement as the rubber on the tires flex that diminishes with larger rims and tire pressure, etc. You'll also have some movement of the axle in the notoriously sloppy upper control arms. Safe to ignore both of those. Or put on a panhard or watts to eliminate that.

Look at the drum vs the backer plate. It will move in and out, but not crazy amounts. I don't have a source for what the correct tolerance is, but probably no more than about 1/4" is pretty normal.

My worn out 8.8 had plenty of slop in it when I pulled it out. It had not changed much over the years and all seemed completely normal. When Trey tore it down to rebuild it for my 85 project, he did find one pin had broken in that 8.8. I think that's also pretty normal and its not going anywhere. I know I must have ran it that way for lord only knows how many miles with no issues. (hmms. No comment about the bluing on the axles at the bearing location)

If you're super annoyed and want to solve it there are a few things you can do. Swap to a 03-04 Cobra IRS. Swap to a 9" or put 9" ends on a fox 8.8 or you can run various C-clip eliminator kits.

My current 8.8 out of a 95 GT also has some of that slop also. Not super worried about it.

No idea how many miles are on my 95 8.8. I pulled the cover and it looked OK. Thats when I learned that my supposed 3.27 gear was actually a 2.73. Oh well. Minimal clutch wear evidence, no visible evidence of bad things like metal remnants in the lub, etc. So I tossed it in without doing anything to it. Soon it will get replaced with another 8.8 I sourced out of an 86. That one will get built out with fox width SN95 flange axles and North Racecar brackets an a 3.90 gear then I'll transfer my SN95 brakes.

Those gears just might be just the kick in the butt the ol beer can on wheels needs. It will at least encourage me to behave a bit more than is historically the case. Or misbehave for shorter bursts and top out 3rd at much slower speeds than is the case now. Lol.

[mudgepondexpress]

My guess is slop in the gear set. The clank sound you hear is transmitting up the driveline. You can jack up the back and have someone step on the brakes while dropping it in gear (auto). or having them stop the wheels then letting out the clutch. You will see the driveshaft move before the wheels do. If it is at its worst when you back up and then go forward, then that is a good sign.

You and also duplicate it by trying to rock it forward and back while it is shut off in gear.

Kenny

[emerygt350]

I had a scary clunky sound but then I realized the exhaust had fallen off a hanger... it isn't something that simple is it?

[lukerbsn]

There is end to end freeplay between the axles and the diff. You can push the rear side to side and it will make a distinct clunk-clunk. That's normal.

Yep, I inspected underneath again today and came to the conclusion it is endplay in the axles. Thank you for the input along with everyone else. For now I will keep driving it until I do the 5 lug swap.


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[homer302]

I had a '98 Cobra new that had upper control arms in the rear that were never torqued at the factory. slow speed driving and going over like a speed hump it would clunk-clunk. Put one of my smaller friends in the trunk and shut it (yes, really) and went for a drive. After about 10 minutes he could "feel" the clunk on the floor pan right over the rear control arms. Put a socket on them and they had never been tightened. Either one of them. Torqued them down and never had an issue since.

[Zap's 85 GT]

Sometimes the baffle inside the gas tank can come loose and bang around. May be something to check.