74 EB, right rear is drooping, WHY?

[Bustedbroc]

Hello, 74 EB, trying to figure out why when viewed from the rear and front wheels pointed straight I have a 1 1/2" droop at the right rear, (measured at the rear bumper end points and visible). I measured axle tube to frame front and rear, measured 9" all around EXCEPT for right rear which was 8". Front bumper ends measure within 1/4' of each other. Recently replaced my C-bushings but truck had same droop prior with factory stock. New suspension all around. Posting some pics. Please ignore the steel plates welded onto the back frame rails. Previous owner had some half ass bumper welded on that I had to cut off. Pics of measurement hard to show due to camera angle but the is approx. 1" difference between left/rt. Shackle are original as are rear body mounts. They looked good enuff to me so I left them. Rear springs are Tom's stock replacement. Right rear spring a bit weak? I didn't notice if there was a droop with the factory springs before I tore it apart.
Thoughts anyone?

 

[75MIKE]

Status of your body mounts?

 

[DirtDonk]

Well, first of all, really clean Bronco!
Underneath is pretty sanitary for being 51 years old.

But second, your shackles are actually on backwards. This may, or may not have anything to do with your lean, but they’re not correct.
Open end faces rearward, away from the spring.

In your fourth picture, what is that plate/bar under the axle tube?

The body bushings may look OK, but they should also measure the same at all eight points. They are 3/4 of an inch tall and should all be exactly the same.
That’s relatively easy to check.

When you installed the suspension, did you leave the spring bolts loose until the vehicle is back on the ground? This isn’t always going to make a difference, but it’s a good practice too wait until the weight of the vehicle is on the ground and loading the suspension, before you torque the bolts. Even though I don’t think this is the majority of your issue, wouldn’t hurt to loosen them and then bounce up and down on the rig a few times and then tighten the back up.

And I’m not clear on what you’re saying about before and after. Did it have the same lean before, or not?
I’m asking because installing C-bushings can make a huge difference in how Bronco sits. They could easily account for this lean all by themselves.

 

[Oldtimer]

Is this a crack?

This offset does not look the same on both sides?

 

[Bustedbroc]

Well, first of all, really clean Bronco!
Underneath is pretty sanitary for being 51 years old.

But second, your shackles are actually on backwards. This may, or may not have anything to do with your lean, but they’re not correct.
Open end faces rearward, away from the spring.

In your fourth picture, what is that plate/bar under the axle tube?

The body bushings may look OK, but they should also measure the same at all eight points. They are 3/4 of an inch tall and should all be exactly the same.
That’s relatively easy to check.

When you installed the suspension, did you leave the spring bolts loose until the vehicle is back on the ground? This isn’t always going to make a difference, but it’s a good practice too wait until the weight of the vehicle is on the ground and loading the suspension, before you torque the bolts. Even though I don’t think this is the majority of your issue, wouldn’t hurt to loosen them and then bounce up and down on the rig a few times and then tighten the back up.

And I’m not clear on what you’re saying about before and after. Did it have the same lean before, or not?
I’m asking because installing C-bushings can make a huge difference in how Bronco sits. They could easily account for this lean all by themselves.

Thanks, shackles on backwards? LOL, I remember when I was putting them back on I figured that they HAD to go on this way, I will flip them.
Not sure what your seeing in pic 4 but it is probably just a flange of the step bar mounting tab the camera picked up.
I will check the body bushings. hesitant on replacing them even though I am sure they are petrified.
No, I did not let the suspension settle, replaced one spring at a time and just socked them down with an impact. No torquing.
It did have the same lean before C-bushings but unknown before I replaces the rear springs and I replaced the rear springs before I did the front end. You may have something with how I tightened the rear springs during install.

 

[Bustedbroc]

Is this a crack?
View attachment 942880

This offset does not look the same on both sides?
View attachment 942881

Hello, I checked, that is not a crack. It is actually a reflection on some white grease that I put on during spring install.
The offset is different if you go by the top of the mounting brackets as you indicate. Not sure if those brackets are identical. I will have to measure but if the are and all things are equal I would think the right side would sit higher not lower.
Thanks

 

[DirtDonk]

Thanks, shackles on backwards? LOL, I remember when I was putting them back on I figured that they HAD to go on this way, I will flip them.

You're not alone. They do look intuitively correct to keep the open face towards the spring. But if you look at other Ford shackles (literally every one that I've ever seen on any Ford truck) then you'll see that the open end faces rearward. Away from the leaf pack.
Now, I've described this bass-ackwards on this forum before. But this time I'm pretty sure I'm correct. Let's let some others comment before you go pulling anything apart.

But the bottom line is, if they are on backwards, they do not have full travel and will interfere with different areas of the hangers and spring eyes.
Some have theirs the same as yours, and have not seen a difference. But when I've tested them, travel was notably limited.
Don't think it would necessarily cause your lean issue, but it's still something that should be corrected.

I will check the body bushings. hesitant on replacing them even though I am sure they are petrified.

It's definitely not a fun job. And not really necessary if they are all the same height. But I'm almost hoping they are not, so that it would at least explain away a tiny bit of your lean.

No, I did not let the suspension settle, replaced one spring at a time and just socked them down with an impact. No torquing.

I would loosen them while the tires are on the ground then. Don't sock them down either. Torque them.
But make sure that the bushing sleeves are what bottoms out on the metal ears/flanges first. Don't distort the poly bushings more than just a tiny bit.

It did have the same lean before C-bushings but unknown before I replaces the rear springs and I replaced the rear springs before I did the front end. You may have something with how I tightened the rear springs during install.

There may be other things to check as well. It would not be the first time a Bronco frame was built poorly from the factory, or that one had been hit and damaged at some point in it's life.
Hopefully it's just some tweaking here and there that is needed.

Paul

 

[Bustedbroc]

You're not alone. They do look intuitively correct to keep the open face towards the spring. But if you look at other Ford shackles (literally every one that I've ever seen on any Ford truck) then you'll see that the open end faces rearward. Away from the leaf pack.
Now, I've described this bass-ackwards on this forum before. But this time I'm pretty sure I'm correct. Let's let some others comment before you go pulling anything apart.

But the bottom line is, if they are on backwards, they do not have full travel and will interfere with different areas of the hangers and spring eyes.
Some have theirs the same as yours, and have not seen a difference. But when I've tested them, travel was notably limited.
Don't think it would necessarily cause your lean issue, but it's still something that should be corrected.

It's definitely not a fun job. And not really necessary if they are all the same height. But I'm almost hoping they are not, so that it would at least explain away a tiny bit of your lean.

I would loosen them while the tires are on the ground then. Don't sock them down either. Torque them.
But make sure that the bushing sleeves are what bottoms out on the metal ears/flanges first. Don't distort the poly bushings more than just a tiny bit.

There may be other things to check as well. It would not be the first time a Bronco frame was built poorly from the factory, or that one had been hit and damaged at some point in it's life.
Hopefully it's just some tweaking here and there that is needed.

Paul

TRying to find a diagram that shows the rear shackles. You guys are the SOURCE on this forum and have bailed me out a number of times. The only thing I found was a parts diagram from LMC truck catalog :

https://www.lmctruck.com/suspension/suspension-front-rear/fbr-1966-77-rear-suspension

and my Haynes manual which shows a "typical rear suspension" illustration and both show the open end forward.

Yet, Nashville Early Bronco youtube video shows him replacing the rear leafs on his 75 and at 1:43 into the video the shackles show rear facing upon removal:

Still have to double check the body pucks.

Thanks.

 

[Oldtimer]

Open towards the back.

And for those who follow on smart phones.

 

[79INA69]

Looking a the 2 pics of the rear U bolts, it looks like the right rear u bolts are showing more threads than the left rear? May be an optical illusion, or the spring pack is thinner on the right rear? As stated, the shackles are on backwards, and final torque on all suspension components is better settled on the full weight of the vehicle at ride height. Another point of measurement (provided the ground is level) would be from the ground to the top of the frame left to right and to the body lines at the fenders. Swapping springs left to right also could eliminate the spring itself. None of which is fun to do at this point

 

[Speedrdr]

Open towards the back.

View attachment 943088

And for those who follow on smart phones.

View attachment 943090

Thanks for the ‘nod’ to us iPhone users! Much appreciated

 

[Bustedbroc]

Open towards the back.

View attachment 943088

And for those who follow on smart phones.

View attachment 943090

Thank you for the clarification.

 

[Bustedbroc]

Looking a the 2 pics of the rear U bolts, it looks like the right rear u bolts are showing more threads than the left rear? May be an optical illusion, or the spring pack is thinner on the right rear? As stated, the shackles are on backwards, and final torque on all suspension components is better settled on the full weight of the vehicle at ride height. Another point of measurement (provided the ground is level) would be from the ground to the top of the frame left to right and to the body lines at the fenders. Swapping springs left to right also could eliminate the spring itself. None of which is fun to do at this point

You are correct, U bolts are from a different source. Right ones were from an auto parts store and long I hacked off the extra length.

 

[Bustedbroc]

You're not alone. They do look intuitively correct to keep the open face towards the spring. But if you look at other Ford shackles (literally every one that I've ever seen on any Ford truck) then you'll see that the open end faces rearward. Away from the leaf pack.
Now, I've described this bass-ackwards on this forum before. But this time I'm pretty sure I'm correct. Let's let some others comment before you go pulling anything apart.

But the bottom line is, if they are on backwards, they do not have full travel and will interfere with different areas of the hangers and spring eyes.
Some have theirs the same as yours, and have not seen a difference. But when I've tested them, travel was notably limited.
Don't think it would necessarily cause your lean issue, but it's still something that should be corrected.

It's definitely not a fun job. And not really necessary if they are all the same height. But I'm almost hoping they are not, so that it would at least explain away a tiny bit of your lean.

I would loosen them while the tires are on the ground then. Don't sock them down either. Torque them.
But make sure that the bushing sleeves are what bottoms out on the metal ears/flanges first. Don't distort the poly bushings more than just a tiny bit.

There may be other things to check as well. It would not be the first time a Bronco frame was built poorly from the factory, or that one had been hit and damaged at some point in it's life.
Hopefully it's just some tweaking here and there that is needed.

Paul

OK, reversed the shackles, checked the body mount pucks, and left all bolts loose (bounced it on the ground a few times), then torqued them down. No difference. Oh well.
I am assuming that the shackles are the same for L/R? Rear most body pucks look very close the the 3/4" piece of wood I slipped them against, both equal. The mid mounts, (behind the cab), look to be in good shape, (see pics).
My Haynes manual says torque to 150-190 ft lbs! Whew, I guess Ford didn't want the springs to fall off.
The shackles are original and probably could use replacement but I don't see anything unusually worn on them to cause this issue. Maybe down the road.

 

[904Bronco]

Open to the Back...

I have got to say I have done a few Broncos, and I looked at all the pictures I have taken... Half were on backwards and the other half was open to the back... I have no explanation on why I did the shackle backwards, I'm guessing that was the way it came apart. So,

Paul, be sure to check your 68 as I could not find a picture to see how yours was...

 

[1969]

You say you have all new suspension. Are you 100% sure the leaf springs are the same lift height? And you weren’t mistakenly sent two different height springs.

 

[DirtDonk]

Not that that would ever happen…

 

[pcf_mark]

I tried to read all the replies but I would check a few things. My Bronco had this and it took a few things to sort it out. The first and most obvious was one tire was not like the other three and was a different height. Oddly when it was on the front it was not obvious but when I rotated then suddenly the rear looked way off. Easy to check. Second thing I did was take the front wheels off and put jack stands under the frame up front. Suddenly the rear looked a whole lot more level - not perfect but not off enough I would care. I then messed with the front arms for days trying to get the bushings to seat correctly so the arms sat on the garage floor in a neutral state. I ended up grinding the mating flanges of the arms to shift them a few millimeters. In the end getting the arms right did make a difference.

As pointed out careful measuring with the frame level also points out strange things that you need to run out. In my example my body was shifted to one side. Frame level on jack stands start measuring down to the ground and see what you learn.

 

[Pops68]

Just spitballin' here - could your front driver's side be higher than the passenger side causing the rear passenger to be lower??? Everyone has been concentrating on the drooping part, so I naturally deviated from that thought process. I AM NOT A MECHANIC or ENGINEER!!!!

 

[DirtDonk]

Just curious too, but have your rear frame horns been replaced? Perhaps for a rust fix, or custom bumper install?
Could the frame ever have been damaged?
Those are also just spitballin' idears. The most common reason for a lean (or at least near the top of the list) are the new C-bushings putting torque into the frame.
But not far behind are, un-equal springs, incorrectly welded perches and hangers, bent frames, etc.

Paul