Lower Control Arm Pivot Bushing

[70 DDDart]

So I scanned this topic and although I might of missed it I did not see anything in FABO that addresses my question.
Recently I was rebuilding my entire front suspension, in the process I was doing the upper CA bushings , replaced them with Energy Suspension urethane pieces. I had looked at the lower CA's and the pivot bushings and as they looked very good decided to leave them alone. On second thought they were maybe 50 years old so lets put in the new ES parts.
So for all readers that have done this, even with a press it is a decent job. As per ES installation instructions I left the outer sleeve of the OE bush in the LCA and "pressed" in the new urethane one with the pivot shaft installed. Pressed means by hand!!!!

Here-in lies my issue. Simply , what holds the LCA on to the pivot shaft? If you are going to rely on the Torsion Bar I have to call BS. My torsion bars have at least a 1/2" clearance between the "retainer clip" when the TB is driven forward into the CA hex. I can't imagine that it will not loosen up after a few miles of driving allowing the LCA to slide back and forth on the pivot shaft. Am I missing something here or these things should be outlawed? I am going to go back to the factory ones, they lasted for the first 50 yrs on the DDart, unless someone can convince me other wise, which at this point is not happening.
One more related question. Can someone tell me what year in the 70's did Mopar change the strut rod length, thread pitch, and nut size? What was the reason?

 

[72bluNblu]

The LCA bushing has NEVER held the control arm on the pin. NEVER. Rubber can not withstand the forces that would be required to keep the LCA from moving backwards off the pin, the rubber would just tear. Just like it does if you tighten the pivot nuts at anything other than ride height.

Which is why there are strut rods. The strut rods keep the LCA from moving forward and backward on the pivot with acceleration and braking. They always have, that’s why the factory put them there.

With poly bushings the length of the strut rod is more critical, which is why I recommend adjustable strut rods with poly or Delrin LCA bushings. The harder material of those bushings allow less play, so the strut rod length is more important.

For A-bodies, the working length of the strut rod, as well as the pitch on the threads, changed in 1973. The reason was that the strut rod bushings were changed for that year, and the thicker bushings required the shoulders on the strut rods that located the bushings to move to account for the additional thickness. This probably had to do with problems with the earlier bushing design, but that’s just a guess.

 

[72bluNblu]

This is a prime example of why you use stock replacement parts instead of the “trick of the day” Bullshit aftermarket “upgrade” Parts.

in my opinion of course.


Why do my urethane bushings squeak

they don’t fit right

they ride too hard

they squeak I’ve speed bumps

they didn’t last

The press fit of the bushing holds it in there. The strut rod provides the triangulation to keep it in alignment while driving. The strut rod connects to the opposite end from the bushing, that’s not what holds it together.

Polyurethane LCA bushings do not work the same as the OE rubber bushings. You have to understand that before you decide to use them. The OE rubber bushings are friction fit into and onto the inner and outer shells. That friction fit does not allow them to slide, assuming the strength of the rubber is not exceeded. If that happens they just tear, rubber isn't very strong. What that means is that the entire motion of the lower control arm depends on the flex in the rubber. Which is why with OE rubber LCA bushings the pivot nuts must be tightened at ride height, because the rubber can only flex so far. The LCA has to be in the middle of the range of travel when the pivot nut is tightened, so, half the motion is flex up in the bushing and half the motion is flex down. Otherwise, the bushing tears, because rubber has very little shear strength.

With poly, or Delrin LCA bushings the material of the bushing is harder. It does not flex like rubber, and so the motion of the LCA can not depend on the material flexing. Instead, with a poly or Delrin LCA bushing the bushing itself has to spin when the LCA moves up and down. That motion should happen at the LCA pivot, the bushing spins on the pivot itself. This is unlike the OE bushings, and because there is motion of the bushing on the pivot pin there must be lubrication. If a poly bushing is squeaking, it is improperly lubricated. Period. This means it was improperly installed, and if it's driven like that for any length of time it will fail prematurely. That's not the bushings fault, that's poor installation and maintenance. There are aftermarket LCA pivots that are greaseable for this reason, you can add grease to the bushing and keep the poly lubricated. That keeps it from failing. Poly bushings are not maintenance free. Properly maintained and lubricated, poly bushings will far outlast rubber bushings. Especially the low quality rubber bushings being made today.

And yes, the fit of the poly bushing in the shell and onto the pin is important. If you buy the kind of poly bushings that come without inner and outer shells, you must assure that they fit tightly. The OE bushing shells are not all identical, the thickness varies, and if the rubber is damaged the shells can be damaged. So you can't just slap poly bushings into the old shells, you have to make sure that they fit with a TIGHT slip fit. As in, they should require lubrication and some effort to put them into the shells. If they just loosely fall into the shells, the shells need to be replaced.

The "problem" with poly bushings is that guys that don't understand that they function differently than the OE rubber bushings they're replacing. They're installed differently, and they must be maintained differently. Instead people think it's a shortcut to get around removing the old inner and outer shells, so they don't need a press. But that only works if the bushings fit tightly in the shells. Like any aftermarket part, you have to check the fit!!! If the fit isn't right, you have to fix it. And poly bushings MUST be lubricated. They should NEVER squeak. If they do, it means they've dried out and must be re-lubricated.

It's no different than anything else. The factory used non-adjustable rockers and hydraulic lifters (mostly). Well, if you upgrade to adjustable rockers and solid lifters, you have to adjust them properly and maintain them. If you do that, you get better performance. But you have to understand how they work differently. If you don't understand that, then you should probably stick with the lower performance original stuff that doesn't require maintenance.

 

[AJ/FormS]

Furthermore;
the actual approximate .5 inch variance in the location of the inboard end of the lower control arm, in the fore and aft direction, makes extremely little difference to the alignment. I couldn't see it in any of my alignments.

 

[70 DDDart]

Thx for the comments, this is not my first rodeo so I understand the differences between OE and aftermarket bushings , how they work, how to install and maintain them , I have been turning wrenches for more than half a century.
When I was reinstalling the rebuild suspension I noticed the different nut and thread on one of the strut rods and initially did not give it a lot of though. I did a rough alignment adjusted the ride height , test fitted my sway bar etc. Stood back and took a good look thinking about the strut rods. I decided to check the fender to tire clearance (front side) there was close to an inch difference side to side. So now I get out the tape measure and measure the strut rods, sure enough there is about 3/8" difference from side to side. up until that time I never knew there was a change but asked a mopar parts guy about the change . He knew about the change somewhere around '74 but was not aware of the length difference. He simply said fine thread or coarse thread.
Anyway the later one is shorter than pre '73 (between the stops) which makes sense given '72 bnb's comments regarding the bar change in '73. On my car on that side, the strut pulled the LCA forward noticably. So I looked at the pivot bushings side to side and sure enough on that side the LCA had been pulled back a 1/4" or so.
My conclusions, after considering the feed back so far. I don't buy the strut rod holding the LCA pivot bush together, I agree with 413's comments. Seems this is proven by the fact that pulling the LCA forward pulled the inboard end of the LCA back without ever driving the car. As far as that not affecting the alignment I can't see that tow and camber are not affected by moving the indoard end that much! The strut rods are a fixed length for a reason, the rubber is there simply to cushion loading and absorb the road for a more compliant feel.
Hope someone else will weigh-in and provide some other alternative to this issue. Right now I am still back to OE.

 

[512Stroker]

Thx for the comments, this is not my first rodeo so I understand the differences between OE and aftermarket bushings , how they work, how to install and maintain them , I have been turning wrenches for more than half a century.
When I was reinstalling the rebuild suspension I noticed the different nut and thread on one of the strut rods and initially did not give it a lot of though. I did a rough alignment adjusted the ride height , test fitted my sway bar etc. Stood back and took a good look thinking about the strut rods. I decided to check the fender to tire clearance (front side) there was close to an inch difference side to side. So now I get out the tape measure and measure the strut rods, sure enough there is about 3/8" difference from side to side. up until that time I never knew there was a change but asked a mopar parts guy about the change . He knew about the change somewhere around '74 but was not aware of the length difference. He simply said fine thread or coarse thread.
Anyway the later one is shorter than pre '73 (between the stops) which makes sense given '72 bnb's comments regarding the bar change in '73. On my car on that side, the strut pulled the LCA forward noticably. So I looked at the pivot bushings side to side and sure enough on that side the LCA had been pulled back a 1/4" or so.
My conclusions, after considering the feed back so far. I don't buy the strut rod holding the LCA pivot bush together, I agree with 413's comments. Seems this is proven by the fact that pulling the LCA forward pulled the inboard end of the LCA back without ever driving the car. As far as that not affecting the alignment I can't see that tow and camber are not affected by moving the indoard end that much! The strut rods are a fixed length for a reason, the rubber is there simply to cushion loading and absorb the road for a more compliant feel.
Hope someone else will weigh-in and provide some other alternative to this issue. Right now I am still back to OE.

Purchase a set of after market adjustable strut rods and set them where you like it.

 

[Dfr360cuda]

So... If the outer shell size is so critical, why does the aftermarket poly bushing suppliers tell you to slide their bushing into a 50 year old shell ? Also use the existing inner sleeve. Why not supply one that's compatable.
I'm not an expert but, wouldn't the poly bushing shrink or swell when the weather changed ? I always thought a tight hole was good. Poly bushings aren't tight, they slide right in.
I've done two rebuilds in the last couple years and I'm sticking with OEM.

 

[512Stroker]

So... If the outer shell size is so critical, why does the aftermarket poly bushing suppliers tell you to slide their bushing into a 50 year old shell ? Also use the existing inner sleeve. Why not supply one that's compatable.
I'm not an expert but, wouldn't the poly bushing shrink or swell when the weather changed ? I always thought a tight hole was good. Poly bushings aren't tight, they slide right in.
I've done two rebuilds in the last couple years and I'm sticking with OEM.

I just did the complete front end of my 67 Barracuda. I rebuilt the LCA's with PST componets their poly graphite bushings and greaseable pivot shafts worked like a dream. The installation was simple you do not use the outer or inner shells the bushings press in by hand very snug and the shaft I had to lightly press into the bushing once in place you torgue the shaft nut to 145 lb/ft and your done. I also used the PST weld on LCA brace. Overall the car rides very nice and is alot tighter control.