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Thread: Lower Control arm bolt comes loose

  1. #1
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    Lower Control arm bolt comes loose

    Lucky I caught this again, the rear bolt in the lower control arm was about to fall out. This happened before and I put locktite blue on it and torqued it to 55'# but it came loose again. While under there I checked the rest of them and the drivers side rear was loose 3/4 turn. It has been years and thousands of miles since last time I checked them, but WTF? I think it may be greasy inside the female threads so I sprayed it with carb cleaner and ran the bolt through a few times. Then I used the blue locktite and put it in and out 3 times with more locktite on each time. I have heard of this happening to others long ago on another group. The bolts had lockwashers, maybe I should try some double star lockwashers? Or should I clean it better/again and use red locktight?
    Tony

    1955 Bel Air Sport Coupe

  2. #2
    Registered Member BamaNomad's Avatar
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    Are you referring to the bolts which hold the control arm shaft to the frame? (75 ft lbs), or the bolts which hold the control arm to the shaft? (55 ft-lbs, but don't torque until the car weight is on the wheels)...

    If your bolts are properly torqued and working out, then something is wrong. I'd suggest removing the bolts, cleaning them thoroughly and lightly oiling and re-installing. These bolts should have a lock washer then the large 'washer', then the rubber. The friction of the rubber should prevent most of it from moving along with the lock washer. I've never thought of putting lock tite on those but I've never heard of them working out. Do you have non-rubber (poly?) bushings??

  3. #3
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    I would just put in new bolts, and use what a lot of OE's do, and use what I think used to be called Stover nuts. The ones that are dimpled so they turn hard, even when installing them. That is what are used on the C4 front suspension, and many other cars. Even good old safety wire, or a cotter pin would at least keep them from falling off. The a-arm bolts also need to compress on a sleeve too.

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    There are about ten or so accounts of this happening on the other group in just one thread, and one post says there was another thread about the same problem.
    Tony

    1955 Bel Air Sport Coupe

  5. #5
    Registered Member chevynut's Avatar
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    I don't see what "problem" new bolts solve. Bolts don't just wear out and start loosening and the old bolts should be fine. There's no reason to replace bolts just to replace them. If it's the a-arm to shaft end bolts loosening, you aren't tightening them correctly or they're turning with suspension travel. Like bamanomad said, they need to be tightened to spec at ride height. If they're turning out, they're not compressing on the bushing sleeve tightly enough to keep the bushing sleeve from rotating or the serrations on the sleeve are worn out. Rubber bushings are bonded to the sleeves and they want to twist the bolt loose as the suspension moves. But if they're tightened properly it shouldn't happen. Millions of cars used the stock bolts and bushings with no problems.

    Do you have the stock rubber bushings or urethane bushings? Urethane bushings aren't bonded to the sleeves and should rotate on them. IMO that makes them better than rubber.
    Last edited by chevynut; 07-04-2018 at 11:41 PM.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

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    Registered Member chasracer's Avatar
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    I think cleaning all the threads again with carb cleaner, let it dry out good and blue loctite would be fine. The way those work from the factory is the inner sleeve has the teeth or knife edging that the large washer rides against - there is friction there and it basically slows the a-arm down. In a drag racing setup, we would take large inside diameter washers that would fit over those teeth and allow the stock larger washer to glide freely. Other guys would grind the teeth down and achieve the same deal. Anyway, this would free up the a-arms and allow the front end to transfer weight back to the rear tires a bit quicker.

  7. #7
    Moderator NickP's Avatar
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    Quote Originally Posted by chevynut View Post
    I don't see what "problem" new bolts solve. Bolts don't just wear out and start loosening and the old bolts should be fine. There's no reason to replace bolts just to replace them. If it's the a-arm to shaft end bolts loosening, you aren't tightening them correctly or they're turning with suspension travel. Like bamanomad said, they need to be tightened to spec at ride height. If they're turning out, they're not compressing on the bushing sleeve tightly enough to keep the bushing sleeve from rotating or the serrations on the sleeve are worn out. Rubber bushings are bonded to the sleeves and they want to twist the bolt loose as the suspension moves. But if they're tightened properly it shouldn't happen. Millions of cars used the stock bolts and bushings with no problems.

    Do you have the stock rubber bushings or urethane bushings? Urethane bushings aren't bonded to the sleeves and should rotate on them. IMO that makes them better than rubber.
    For the most part I would agree with this complete statement. Actually, I don’t disagree but just question it in theory. If the assembly was correctly assembled at rest, all components of proper size, serviceable or new, the action of the bushing/serrated sleeve against the cup washer really shouldn’t try to disengage the bolt/lock washer. True,the action of the CA in one direction may appear as though it would possibly rotate the cup washer/lock washer/fastener in one direction but the reverse motion back to, at rest should have the opposite rotational effect rather than a continual unlocking (for the lack of a better term) of the assembly. The function of the assembly is very dependent upon the condition of the parts and the proper assembly method as mentioned.
    Last edited by NickP; 07-05-2018 at 08:18 AM.

  8. #8
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    The bushings are poly and tightened to 55'# more than once, with blue locktight. Like I said above, there are quite a few other accounts of this happening if you know where to search for it.
    Tony

    1955 Bel Air Sport Coupe

  9. #9
    Registered Member chevynut's Avatar
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    I think your poly bushings are made wrong (too long) and they're being compressed end-to-end too tightly by the washer. I took some length off of my poly bushings in my C4 front and rear so they would rotate around the sleeve as they're designed to do. My IRS would not articulate properly until I did that even with lube. I think the manufacturers make these things with crappy specs and tolerances and the mating parts have tolerances too. I would remove the washer and take some material off of the bushing by sanding or machining and leave the sleeve full length for the washer to bottom out on. A little compression of the poly isn't bad, but too much will turn the washer and therefore the bolt comes loose like you're experiencing.

    Also lube the backside of the washer that faces the poly bushing with the proper lube.
    Last edited by chevynut; 07-05-2018 at 11:46 AM.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  10. #10
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    Anyway you look at it, the bushing sleeve needs to be slightly longer than the bushing, and fit snuggly in between the mounting ears so the bolt can clamp the sleeve securely in place without binding up the bushing. If it was about to fall out like you said, it could wear the mounting holes in the frame oblong, and create new problems. I've never had an a-arm bolt loosen even with poly bushings, so you should easily find the reason for why it won't stay tight, because something's not right.
    Last edited by 55 Rescue Dog; 07-05-2018 at 11:46 AM.

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