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Step on the brakes, and CLUNK! in the right front


fredges

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My '69 521 brakes OK, but sometimes, when I'm approaching a light or a stop sign, there's this pretty loud CLUNK! that comes from the right front. I don't know WTF it is. But it always startles passengers, because you can feel it through the body. Weird. Guess I'll just keep pounding on it until something falls off, then I'll know what it is... 

Anyone had similar problem and live to tell about it? Maybe this belongs in suspension? I don't fucking know... I've crawled around underneath it and can't understand why it's doing this...

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Inspect the tension rod. You can see the nut on the end of it just under the right side of the rad. It's a long straight rod going back to the lower control arm. The bushing may be worn out and it's loose.

I will do that! Soon! That answer sounds like that could be it. It isn't making the clunk sound every time I stop. usually when I first start out of the garage, after sitting a while, or after going down the road a ways without turning or braking for a while. 

I will report back with my findings after I get my old, creaky, freezing ass under the truck... 

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^^^ this. If it's bad enough, someone standing out side the truck will be able to see the wheel actually shift backward and forward inn the wheel well as you brake and accelerate.

I will call my bro to come over and have beers whilst watching to see if the wheel shifts. (that shithead's finally good for something!) Good advice. Thanks. 

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Mike, what's up with poly ?

 

Was looking to go that way after installing 'new' rockauto ones a year ago, and having them beat out right away.

I think the ones they sent me were as old as the truck, and all dried out, or shelf rotted.

 

Oh, and fredges, mine does the same clunk thing, and I am sure it's because of the failed rubber bushings.

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Rubber does not break, it gives.

 

 

The tension rod has to be supported but allowed to move up and down. Poly is way too stiff and the bar will have to flex and like repeatedly bending a piece of wire it will shear from metal fatigue...

 

DatsunTCbroke1.jpg

 

DatsunTCbroke3.jpg

 

Rubber is compliant and allows limited movement.

 

 

On other suspension components such as LCA and UCA bushings, the rubber grips both parts and will flex internally to follow the small twisting movement. Poly won't, and what happens is one surface will simply slide against the metal. This causes squeaks and wear. Poly is a 'racing thing' where they are inspected and maintained. For a street car you will get a better ride from replacing old ones with rubber. To those that think poly gives a better ride, two things...it does handle better because you are comparing it to old soft, cracked or rotten rubber ones that are 40 years old and the placebo effect.... the more you spend on something the better it works. When you get tired of the squeaks, too firm ride and holes that are now oval from wear try rubber.

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I was kidding, datzenmike ... it's an old SNL skit ... nvmnd. :D But yeah, what you say makes total sense. 

 

I'll check that rubber bushing and stuff was soon as it's warm enough to open the door to the garage. It's like my garage is refrigerated or some shit. Crazy freakin' cold in there...

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All of the above.....except that if it was suspension related, you'd be getting the clunk on bumps too, not just braking.  Also check the bolts that hold the backing plate to the spindle.

 

Mike's right about urethane on the tension rod being bad.  You can drill the bushings to soften them up, but new rubber ones should be fine.  I have urethane UCA bushings for the dogbone.  You can still get new rubber ones on rockauto, but they've always worn out in in 6mo to a year if you drive much.  My site is in the signature block.

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