Torsion Bar Finger in LCA Rubs frame

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racerdude5

racerdude5

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So approximately 2 months ago my 74 duster began to develop a click when the suspension travels, the sound IS the torsion bar finger rubbing the sub-frame. Well, we replaced the lower control arm bushing, shell and all and replaced the strut rod bushings. The sound went away for 2 weeks and now the sound is back. Perhaps not as severely but it still does it. I put in polyurethane bushings. The car has been hit on the side which is having the problem, I'm not sure of the severity but since then all the components have been replaced. The sub-frame and k member look square and undamaged. The LCA shaft is straight. The wheel bases on the side with the problem is about half an inch shorter. When we removed the LCA assembly to replace the bushing, the shaft was crooked in the LCA and the bushing was destroyed. But since we fixed that, what could be causing this? Has anyone had any similar experiences? What's the best way to check to see if your car is square at the wheels, K member, and sub-frame? Please I need some help. :banghead::banghead::banghead:#-o#-o#-o
 

This can happen if the torsion bar is clocked incorrectly in the LCA, or if the bars are worn out. If your torsion bars are stock, you probably have the adjusters cranked all the way in to keep the car at the ride height you want. When that happens the adjusters can contact the frame.

If the car has been hit, it would be wise to measure the frame points listed in the service manual and see if they match up. I'll see if I can post up the dimensions.

***Edit***

You can download the '71 Plymouth Body Service manual here, the dimensions for your Duster should match the "Valiant" specs on pg 294

http://www.mymopar.com/downloads/servicemanuals/1971_Plymouth_Body_Service_Manual.zip

There are all kinds of service manuals listed over at mymopar. Really helps to have a copy of the body and chassis service manual for your car if you don't have one already. Nothing listed for a '74, but there's '70 and '71 for Plymouth's, and the frame dimensions didn't change. There's a '73 Dodge manual that would have all the disk brake specs too.

http://www.mymopar.com/index.php?pid=109
 
Daves69 said:
I don't know of differences in 73 Dart vs 74 Duster.
You can download the Dart Body Manual here for reference...............

http://www.mymopar.com/index.php?pid=109
Click to expand...

Duster has a 108" wheelbase, Dart has a 111" wheelbase, so the long diagonal measurements will be off. K frame and all the subframe points are the same, the additional length is in the floor between the front and rear subframes.
 
Very good point but the torsion bar finger should still be able to clear the subframe and as far as worn out torsion bars go, when I took it out it had a twist in it. Like the hex's on the ends were not aligned. They were off by about 30*
 
racerdude5 said:
Very good point but the torsion bar finger should still be able to clear the subframe and as far as worn out torsion bars go, when I took it out it had a twist in it. Like the hex's on the ends were not aligned. They were off by about 30*
Click to expand...

Not true. The torsion bar adjusting levers do not clear the subframes, ie, they can not be rotated freely past the subframe, they hit it. You can check this by removing the torsion bar, the adjusting lever should then spin freely, and it will hit the subframe as you rotate it clockwise. It's like that on all of my A-bodies and every single one I've ever seen.

The only reason they don't normally hit is because the adjusters usually aren't sticking up far enough to contact the frame with the normal range of suspension travel. But, if the adjusting bolts are run all the way in on a sagging set of stock torsion bars, there isn't enough travel, or spring resistance with the weak stock bars to stop them from hitting the subframe.

And yes, all factory stock torsion bars are clocked at 30*. There are two positions that can usually be used to install the LCA's, those positions are one "flat" apart on the torsion bar socket. That's why you install the LCA's at full "droop" with the adjusting lever against the adjusting bolt plate, so that the torsion bar is clocked correctly in the socket.

Is this a slant 6 car that now has a V8?
 
Ohh.... But why didn't it ever do it before? And why does it do it sometimes but not others? Its a v8 car. So the torsion bars should have a twist in them?
 
racerdude5 said:
Ohh.... But why didn't it ever do it before? And why does it do it sometimes but not others? Its a v8 car. So the torsion bars should have a twist in them?
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The torsion bars should not have a "twist" in them, but the hex ends on the stock bars are offset if that makes sense. If the bar actually has a twist you've got problems.

As far as it not doing it before, I would hazard a guess that either you have accidentally changed the adjustment on the torsion bar adjuster, which has put the lever closer to the frame (and probably raised the car a slightly). It's also possible that the alignment on the car has changed and that's causing it.

Have you had the car aligned since you replaced the front suspension bushings? If not, this needs to be done given the amount of work you've done on the front suspension. Especially since you replaced everything with poly bushings. They are not the same as the stock pieces, and you need a new alignment after installing them.

Even if the car has been aligned, and has the correct V8 torsion bars, it could also just be that the 40+ year old torsion bars have sagged to the point that you've run out of adjustment. The factory torsion bars had ridiculously soft spring rates, and the bars do "sag" over time, just like leaf springs. While the spring rate doesn't change, you do lose adjustment. Could just be time for a new set of bars, which is a good idea anyway because of how badly undersprung these cars were even brand new. I wouldn't ever install torsion bars with a diameter smaller than 1" again, the lack of handling performance is appalling compared to newer, larger torsion bars.
 
Ohhh okay so the hex heads are offset. Thank you so much for the info, it definitely needs an alignment. However on that same side, every time I get it aligned the alignment goes out due to the cams in the upper control arm turning. So you have any experience with this issue?
 
racerdude5 said:
Ohhh okay so the hex heads are offset. Thank you so much for the info, it definitely needs an alignment. However on that same side, every time I get it aligned the alignment goes out due to the cams in the upper control arm turning. So you have any experience with this issue?
Click to expand...

If they're torqued to spec they shouldn't turn. Could be they're worn out as well, they do sell new cam bolts. Could also have been an issue with all of the worn out bushings. Or maybe they just need new lock washers and nuts.

When you get it aligned just put a scribe mark on the washer and mount so you know where the cams are supposed to be. That way if they do move you don't have to have it re-aligned.
 
Wow, I just realized that the problem is probably the lca shaft nut. That would explain the problem being solved after I reinstalled the lca and torqued the nut. Since the problem is continuing to worsen and the fact that there was NO problem for almost 2 weeks after the installation, I tend to believe it is that. When I dissassembled the lca assembly (to replace the bushing which was also when the problem was the worst), the lca nut was only finger tight. I'm assuming that over time the nut has loosened with the constant up and down motion of the lca which causes the lca shaft to pivot. Since the shaft would pivot with the lca, the nut (which is tightened up against the stationary k member) would not want to turn with the shaft. Resulting in it loosening itself.
 
That doesn't seem right. The LCA nut should not loosen. That nut is huge. The shaft does not pivot -- that's why there's a bushing. You should tighten the nut with the cars weight on the suspension, at normal ride height. Otherwise, you will be locking "twist" into the bushing, which will damage it over time.
 
mvh said:
That doesn't seem right. The LCA nut should not loosen. That nut is huge. The shaft does not pivot -- that's why there's a bushing. You should tighten the nut with the cars weight on the suspension, at normal ride height. Otherwise, you will be locking "twist" into the bushing, which will damage it over time.
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This, although the polyurethane LCA bushings do not lock the pivot into place like the originals so tightening the nut with weight on the suspension is unnecessary. However, the stock LCA pivot nut should be tightened to 145 ft/lbs, so, it shouldn't be rotating any at all. The poly bushings also should be used with adjustable strut rods IMHO, simply because they do not function the same way as the original LCA bushings. The length of the strut rod is even more important because the poly LCA bushings can slide fore and aft on the pivot, so the strut rod does more to locate the LCA using the poly bushings.

Regardless, it's unlikely that would cause the LCA lever to hit the frame. That's mostly a function of how much the lever "sticks up" from the LCA, and that's completely determined by the torsion bar adjusting bolts and the clocking of the LCA on the torsion bar.

Sounds to me like you need to torque everything to the specs in the manual. The UCA cam bolts are supposed to be torqued to 65 ft/lbs, and the LCA pivot shaft nuts are supposed to be tightened to 145 ft/lbs according to the manual. I know Firm Feel calls for 100 ft/lbs on their LCA pivot shafts, but they use lock nuts. So, none of those nuts should be loosening up.
 

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Okay, nut was tight already to spec. Its not that. Taking a look at the torsion bars now. Thanks for the help!
 
Looking into ordering a new set of bars! Gonna eat a hole in my wallet for sure.
 
Alright, you're sure the problem is due to torsion bars? I'm ordering a 1.03 set from PST. The thread on here regarding there bars makes me very confident in their products and their response to their customers.
 
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