Pivot shaft & poly bushings mystery

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like_A_pike

that's not factory
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1968 barracuda w original 318 torsion bars and slightly sloppy LCAs but not terrible.

Symptoms: when car is raised, after adjusting ride height (wheels on the ground) the car sticks up about an inch or so higher than where it was set. Drive around a bit and it settles down to the adjusted position.

I thought my adjusted struts were wrong and binding but I had the suspension cycling really well. Let the car down and adjusted it to ride height. Then I went to tighten the pivot and struts down and found that the passenger side wasn’t tightening- at all. Decided to take a look at the LCA bushings. I was sure that I would find shot 57 year old rubber bushings.
Nope:
IMG_2563.jpeg


So my first question is how does one tighten the pivot to 100’lbs if there is zero resistance inside this bushing?

Maybe something wrong with the application?

IMG_2561.jpeg


Does that not look like the inner shell of the old bushing? Does that look correct?

IMG_2564.jpeg


I can push the pivot into position with a hand??!

As far as my symptoms go, I feel like the LCA is just slopping around in there and binding.

What do ya’ll think?
 
the poly bushing utilizes the rubber inner and outer "sleeves" as part of the assembly. it's not unusual for them to push together by hand, as long as they're not all waller'd out.

the torque isn't *as* critical with the poly set up as it is for the rubber bushings. never the less, it should be *tight*. i do it up with the weight of the car on the tires and always add a dab of red loctite. in some instances i've used a bar to give it a little pressure to the nuts to bite.
 
The bushing came about halfway out when I pried the LCA off the stuck pivot. I did not see the outer shell in there though. All of the holes are still round in the arm and k frame and the poly is fine.

I’m kinda leaning towards replacing the rubber bushings.
 
That's perfectly normal. When the car is lifted, the suspension goes to full droop and the camber goes full positive. After you let the car back down, the tires have to rotate a few times to allow the suspension to settle.
 
You should be able to put a long prybar between the inside of the LCA close to where the bushing is and the K frame and pry hard on the LCA to put it all in a bind to hold the pin still while you pop the nut with an impact gun. Once you get it tight enough to keep the pin from turning, you can torque it to spec if you want. I'd just tap it on down with the impact.
 
The bushing came about halfway out when I pried the LCA off the stuck pivot. I did not see the outer shell in there though. All of the holes are still round in the arm and k frame and the poly is fine.

I’m kinda leaning towards replacing the rubber bushings.
if they were done a long time ago, they might not have them. the new stuff is *much* better and utilizes the outer shell (or supplies their own) and the new greaseable pins are nice.

good quality rubber units are so few and far between today, so watch that when buying.
 
It seems strange that I can cycle the entire assembly until I adjust the ride height. Then I can’t get a jack to raise the LCA all the way up without the wheel on?!
 
It seems strange that I can cycle the entire assembly until I adjust the ride height. Then I can’t get a jack to raise the LCA all the way up without the wheel on?!
And you won't with the ride height adjusted.
 
I am attracted to the derlin combo from Bergman autocraft and boxing the arms up after squeezing the LCA in a bit. Jim Lusk made a video on the subject a dozen years ago!
 
I am attracted to the derlin combo from Bergman autocraft and boxing the arms up after squeezing the LCA in a bit. Jim Lusk made a video on the subject a dozen years ago!
I have the Bergman stuff for Vixen. When I finally get a round to it.
 
I had a new rubber Moog bushing give way while driving my Roadrunner, scary even at 40 mph. It may have been faulty or it may have been user error as I've never been sure how or when to tighten to adjust the ride height when rebuilding with rubber suspension parts. I have rebuilt and replaced suspension parts on probably a dozen cars with no problem, but I alway question the method.
Fast forward to my 70 Duster front suspension rebuild/upgrade where I used the BAC Delrin LCA bushings. The nice thing about them is you can tightened the pivot nuts to "spec" forever and have the ability adjust your ride height when and wherever you want without "tearing" them like you might rubber bushings.
 
I sent BAC an email earlier yesterday with a few questions. This guy Peter Bergman writes me back!! The website seems to suggest that they are going racing this weekend too; so pretty busy and still took the time!!!

Add that to all of ya’lls endorsements-

They are on the way!! I gotta get cracking on getting the other one out and cleaning them up!
 
I sent BAC an email earlier yesterday with a few questions. This guy Peter Bergman writes me back!! The website seems to suggest that they are going racing this weekend too; so pretty busy and still took the time!!!

Add that to all of ya’lls endorsements-

They are on the way!! I gotta get cracking on getting the other one out and cleaning them up!
i just bought a complete borg set up and some other bits from him. he ships fast and communication is great. super solid dude. can't go wrong with those parts.
 
Well they don’t have to be too fast, the other lower ball joint isn’t giving up! -and I think the old outter shells ARE still in place too….
 
I think you need to leave the outer sleeves for the new delrin bushings...
 
Looks like I’m getting a ball joint and the retaining clip was AWOL behind that torsion bar! This LCA just slipped right off the bushing too. Currently scoping out 1 3/8” taps …
 
Symptoms: when car is raised, after adjusting ride height (wheels on the ground) the car sticks up about an inch or so higher than where it was set. Drive around a bit and it settles down to the adjusted position.

This is 100% normal. As you raise the car the suspension extends until it's sitting on the bump stops. When you lower it down, the suspension is on the bump stops when the tires hit the ground. Because of camber and toe changes at full suspension extension, the wheels are not in the same position as when it's at ride height. But, the friction from the tires tries to keep the wheels in the same place. So, until the car rolls the suspension will not fully settle.

So my first question is how does one tighten the pivot to 100’lbs if there is zero resistance inside this bushing?

There's a few ways to tackle this. One is to just use an impact, sometimes that's enough to get the lock washer to grab before things start spinning. But if you're using a factory lock nut or even a Nylock the nut itself may have too much resistance and you'll have to grab onto the shoulder of the pivot pin with a set of channel locks to overcome the friction in the nut.

On that note, you can just use a standard nut on those pivots, with a nice new lock washer, because at 100 ft/lbs it's not coming loose.

The other thing is, because there's no rubber bushing you don't have to tighten the pivot nut at ride height. The poly and Delrin bushing slip on the pivot, so, you can install the pivot by itself into the K frame, use some channel locks to grab the shoulder of the pin (not where the bushing rides!!!) and torque the nut to 100 ft/lbs. Then you can just slide the LCA onto the pivot.
View attachment 1716394397

Does that not look like the inner shell of the old bushing? Does that look correct?

That's the inner shell, and that is 100% correct for most poly bushings if you're reusing the factory pins. There are aftermarket pins for poly bushings that don't have the machined step for the inner shell, they're the same diameter all the way down the pin. Some of those are greaseable, some are not. Either way, with factory pins and most poly bushings you need both the inner and outer shells.

View attachment 1716394401

I can push the pivot into position with a hand??!

Normal. With the poly bushing the fit between the bushing, pivot and LCA should be a tight slip fit. They should assemble by hand, but not have any end play. Poly and Delrin bushings do not work anything like the original rubber bushings, the bushing rotates on the pivot. Which is why they need to be greased.

As far as my symptoms go, I feel like the LCA is just slopping around in there and binding.

What do ya’ll think?

Unless there's a ton of end play on the pivots nothing is slopping around. And again, the symptoms you describe with the suspension not fully settling without rolling the car are 100% normal.

I sent BAC an email earlier yesterday with a few questions. This guy Peter Bergman writes me back!! The website seems to suggest that they are going racing this weekend too; so pretty busy and still took the time!!!

Add that to all of ya’lls endorsements-

They are on the way!! I gotta get cracking on getting the other one out and cleaning them up!

Peter is great, and the Delrin bushings are great. But they won't change a thing with regard to how the suspension needs the wheels to roll to fully settle.

And they may not change anything with the issue of the pivot spinning in the bushing either. The Delrin bushing works exactly the same way as the poly bushings do, although they do not require the outer shell to be re-used and the material is harder. They still need the inner shell or aftermarket pivots. They should still be a tight slip fit on the pivot, so hand assembly is not unusual. Because the material is harder the fit between the pivot and the bushing is even more important, if there's any play between the bushing and pivot you need better fitting pivots.

When I installed the Delrin bushings in my Duster I measured half a dozen different pivot pins- factory ones with inner shells, and a couple different aftermarket pivots designed for poly/delrin bushings. The factory pivots and inner shells have a fairly wide tolerance because the bushing manufacturers never really had to hold the outer diameter of the inner shell with any real exacting spec. And even the aftermarket pivots have some variation to them.
 
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I sent BAC an email earlier yesterday with a few questions. This guy Peter Bergman writes me back!! The website seems to suggest that they are going racing this weekend too; so pretty busy and still took the time!!!

Add that to all of ya’lls endorsements-

They are on the way!! I gotta get cracking on getting the other one out and cleaning them up!
He's a good dude. I've spoken with him on the phone a few times. He's on here a lot. His stuff is expensive because it's quality and innovation. His accessibility and honest approach are two big reasons I did business with him and likely will again. He cares about his products and his customers.
 
For the record or for science, I will say that after 65,000 miles and 14 years without lubricating the poly bushings that I didn’t know I had, and cleaning the dirt out of them, they may still be serviceable! Lol.

I think my slop issues were likely caused by “end play” due to a combination of things. First the gap and flexibility between the sides of the LCA on the pivot end. Not that 57 years hasn’t played a roll but I think one of mine was tack welded well after lunch break on the assembly line. It’s pretty floppy. I suspect that the bushings have worn a bit with my mistreatment. But they will function on dry silt without squeaking! I know that the pivots were not tightened and I think that enabled the spring (T bar) to walk up and down. Maybe enough to loose a retainer clip? I don’t know.
Once the struts were backed off I could twist the LCAs on sloppy T bars and pivots.

It was time I got to these even if only to lube them and properly tighten the pivots. But I bet (about $160) that I’ll be happy with having new lubed derlin bushings on shafts that were made for them too though.
 
If the pivots were actually loose you need to check the pivot tubes in the K frame, they’re only tack welded in place on the inside of the K frame and it isn’t unusual for them to break loose. I would check the inside of the tubes for any wear (the pivots aren’t supposed to move) and make sure they’re still welded in place. If there’s any evidence of metal on metal wear inside the tube you may have to think about replacing the tubes.

The retainer clip was likely just left out. The torsion bars don’t move around enough that deep in the socket to have popped it out.

Make sure to check the fit between the Delrin bushing and the pivot shaft. It needs to be a tight slip fit or even a light press fit.

Based on your pictures in the other thread, if the old poly bushings were still tight slip fit and didn’t have any obvious worn spots they’d probably have been fine.
 
Good point! A spell or two with leaking valve covers may have helped as there is plenty of lube in both tubes. The pivot rocks a tiny bit when inserted all the way into the K frame
 
Good point! A spell or two with leaking valve covers may have helped as there is plenty of lube in both tubes. The pivot rocks a tiny bit when inserted all the way into the K frame

I mean they’re not a press fit or anything so without the pivot nuts tightened a little end play is to be expected. But they need to not have any when tightened.

If the pivot nuts were loose, I’d make sure to clean everything thoroughly and inspect for any wear, cracks, or looseness in the tubes and the K frame around them.
 
The LCA sides look solid. Hard to say on the other side. Tube seems smaller than the hole on that side. For the taper i reckon. It will need a little cleaning but I believe it’s good. Thanks
 
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