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Radius arm axle bushing degree question ??

buckroseau

Jr. Member
Joined
Mar 15, 2017
Messages
70
I'm sure this topic has been beaten to death, but looking for maybe a little more insite here.

I've got a 75 Bronco I finished restoring a little over a year ago. Pretty much everything new from the ground up. At highway speeds (60 mph) it has a slight hunt / wander whatever you want to call it. It has all new ball joints, steering box, bushings, etc. I have the 6 turn box. I have about a 3" lift in it.

Last year I had a front end alignment done, results attached, angle seemed correct. Someone had told me to try increasing the angle from 3 degrees to 7 in the front axle radius arm busings. I assumed that 3 degree's were in there, I ordered up a new set of 7 degree busings, I just pulled out the ones that were in there that came with the lift kit and they are 7 degrees.

I guess my question is, with a 3" lift, the bushing instructions say I should have a 4 degree bushing for a 2" to 4" lift. Should I order up and install the 4 degree bushings? And if yes, am I going to the right direction for this to help?

Any info appreciated.

Thanks, Matt
 

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Broncobowsher

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Jun 4, 2002
Messages
34,833
I think you are confusing measured caster with caster correction.

Your numbers look pretty good. Stock caster is very low, something like 0-1°. The 4° bushings are an offset from stock. The correct for the caster lost when you lift it. With 3" of lift you loose about 4° of caster. The old school thought was return to stock specs. Modern school (with power steering) is more caster is better. The 7° bushings have 7° more caster then stock bushings.

If you started at 0°, lifted 3" and get -4° of caster. Take that and put 7° correction and you get 3° of actual caster. That is better then stock.

I see a drop pitman arm. Does it have a drop track bar bracket as well? Is it just bolted in?
What about rear springs? The tail can wag the dog.
 
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buckroseau

Jr. Member
Joined
Mar 15, 2017
Messages
70
I think you are confusing measured caster with caster correction.

Your numbers look pretty good. Stock caster is very low, something like 0-1°. The 4° bushings are an offset from stock. The correct for the caster lost when you lift it. With 3" of lift you loose about 4° of caster. The old school thought was return to stock specs. Modern school (with power steering) is more caster is better. The 7° bushings have 7° more caster then stock bushings.

If you started at 0°, lifted 3" and get -4° of caster. Take that and put 7° correction and you get 3° of actual caster. That is better then stock.

I see a drop pitman arm. Does it have a drop track bar bracket as well? Is it just bolted in?
What about rear springs? The tail can wag the dog.

Yes, drop pitman arm. It does have a drop track bar bracket, it is bolted in. Rear springs seam tight, the wander does seem to be coming from the front end.

This is very frustrating, seems like some say that their Bronco's drive like a sports car on rails, stright down the road. And mine, I'm afraid to let my wife drive it. Seems like there a silver bullet answer or fix to this problem and I'm just not getting it.

Matt
 

.94 OR

Contributor
Bronco Guru
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Jul 5, 2009
Messages
1,659
Tire pressure?

Tie rod end slop?

Steering box slop?
 

Letsgocrawling

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Sr. Member
Joined
Aug 26, 2008
Messages
513
Loc.
Tucson Az.
I think you are confusing measured caster with caster correction.

Your numbers look pretty good. Stock caster is very low, something like 0-1°. The 4° bushings are an offset from stock. The correct for the caster lost when you lift it. With 3" of lift you loose about 4° of caster. The old school thought was return to stock specs. Modern school (with power steering) is more caster is better. The 7° bushings have 7° more caster then stock bushings.

If you started at 0°, lifted 3" and get -4° of caster. Take that and put 7° correction and you get 3° of actual caster. That is better then stock.

I see a drop pitman arm. Does it have a drop track bar bracket as well? Is it just bolted in?
What about rear springs? The tail can wag the dog.

Threads like this are great, always thinking ahead in case a problem such as this awaits me with my project lol. With BB's last comment in his quote you can check to see if your truck dog tracks...meaning check from behind at speed and see if drives strait, if it does that pretty much eliminates the arse end. I have seen multiple times where alignment numbers look good but the dog tracking is still there.
 

Broncobowsher

Total hack
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Jun 4, 2002
Messages
34,833
Check that track bar drop bracket very carefully. Are there any signs of it walking around? I'm not talking huge amounts, nothing like 1/4". I'm talking tiny amounts, like 1/64". If you can a couple of beefy tack welds. I'm not a fan of the huge full burn in, makes it harder to get off later when you go to repair frame cracks or go to a track bar riser bracket on the axle. Just enough weld to keep it from walking around.
 

DirtDonk

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Messages
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How did he change the rear axle camber and toe-in exactly?
And I see that between one chart and the next the readings on the right front wheel changed. I suppose they could have changed to to the pretty big toe-in change he made, but I don't do geometry unless I have to.;):p

All boxes checked

How so? What pressures are you running, and have you experimented with different pressures since you noticed the wandering?
And speaking of that, did you have the same feel on the road before the toe-in change? Or just after?
Toe-in can definitely change how it feels in the real world. Just a 1/16" difference can be felt by someone that's got some seat time in Broncos.
Air pressures the same way. So curious what you're running.

But now for the trackbar bracket. When I installed mine I could absolutely feel a slight wandering. Very slight, but the rest of the rig was pretty dialed in and I could feel little changes.
Doing "the test" revealed a lot of flex with a bolted trackbar bracket.
Welding it in addition to the bolts took care of it.

The first time I had some wandering that I noticed could not be "tuned" out, it was the lower trackbar bolt flexing on it's cracked weld.
That big lower stud is actually a hex-head bolt stuck through the lower bracket and tack welded on the inside where you have to lied down under the axle and look up under the bracket to see it.
Re-welding this took care of that particular bout of wandering.

So even though more caster would likely help some things, the first thing I'd do would be to perform the test you've probably read hereabouts where, with the full weight of the vehicle on the tires, a helper turns the wheel back and forth while you check for anything that is even the most slightly loose. If one thing is loose, you can get wandering. If more than one thing is loose, they work together to create more wandering.

At some point you will need to weld the trackbar bracket. If you're sure it's correct, and both bars are parallel and even, the bracket should get welded.

Paul
 

Broncobowsher

Total hack
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Jun 4, 2002
Messages
34,833
As for the tire pressure, that can be sensitive as well. Not just that they are filled. If you filled to the max load capacity on the sidewall you got it really wrong. I was running 30 on the street, did good. After some time I was noticing a little more crown wear in the tread then I liked. I could drop to 28 and it was still about the same. But drop to 26 and it went all over the place. I would sometimes get lazy and not keep up on the tire pressure when I let it sit for some time, looked good so I drove it. Before I was out of the neighborhood I knew I had to go home and put a little air in each of the tires. The rears were more sensitive then the fronts, probably the Detroit locker.
 
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buckroseau

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Mar 15, 2017
Messages
70
I really appreciate all the feed back, I am trying to work the problem on my end.

I took a look at that track bar bracket and I do not see any signes of movement, not even a little? I remember putting this in and it took the big hammer and I laid into it pretty hard with the impact wrench? I was hoping to see something, but didn't expect it.

As far as tire pressure, generally I'm in the 30 to 32 range. I had a slightly more aggressive tread on the truck right away, but ended up selling those and getting a more streetable tire, hoping that would help...it did not.

Another quick question, I took a pic of the rear leaf spring, it still has the part number on it with the sticker. I am wondering if anyone can tell me what size lift this is, 2.5" or 3". You may ask, "why doesn't this guy know", this vehicle has been in my life for about 14 years, but I took it across the finish line a little over a year ago. Little bit of the back story in this thread.

http://classicbroncos.com/forums/showthread.php?t=275779

I'm just wondering if I went to a 1.5" coil and rear leaf spring and stuck with the 7 degree radius arm bushing, if that would make a significant difference?

Thanks, Matt
 

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68ford

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Dec 26, 2004
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Those springs are 2.5 lift and if your frame is a 1975, you have the wrong track bar drop bracket. Your bracket is 76-77. But as long as it's in there and tight, I doubt it's causing an issue.
 

Slowleak

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Mine had a little wander at highway speed and I figured it was just normal wear. I thought my trackbar bushings were in decent shape and I did not see any signs of movement. Just to be sure, I set my phone to record video and stuck it under the axle end of the track bar. Then I cranked the wheel back and forth while it recorded. Turns out I had a lot of play in the bushing. A new rubber one took all the wander/drift out of it.
 
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buckroseau

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Mar 15, 2017
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Those springs are 2.5 lift and if your frame is a 1975, you have the wrong track bar drop bracket. Your bracket is 76-77. But as long as it's in there and tight, I doubt it's causing an issue.

Do you have a link to the correct one? Got this one from Bronco Graveyard.

More than happy to purchase the correct one if there is a chance it may resolove this issue.

Matt
 
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buckroseau

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Mar 15, 2017
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Mine had a little wander at highway speed and I figured it was just normal wear. I thought my trackbar bushings were in decent shape and I did not see any signs of movement. Just to be sure, I set my phone to record video and stuck it under the axle end of the track bar. Then I cranked the wheel back and forth while it recorded. Turns out I had a lot of play in the bushing. A new rubber one took all the wander/drift out of it.

Where did you get rubber bushings?

Matt
 

Slowleak

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Where did you get rubber bushings?



Matt



It took a lot of searching to find the part numbers. Then I found the bushings on eBay.

Here’s a picture showing the part numbers. The “C5” part number is the oval bushing for the frame end on a ‘76-‘77. The “C6” part is the round one for the axle end. It came in a box of two and I believe that is the same bushing that fits both ends of the earlier track bars.
36323e2e70f1fa73e2b5f1c2115afc4a.jpg
 

68ford

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Dec 26, 2004
Messages
2,710
I may have missed you with the yr of track bar bracket. I have always seen bracket "go over" the existing frame bracket on 66-75. Yours is on the inside like a 76-77. But that heavy duty one you posted for 66-75 goes inside like yours. So that makes me think you have that heavy duty one you posted.
 

DirtDonk

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Correct. Graveyard's bracket goes on the inside, so likely that is the correct bracket. If not, it at least looks like it fits very well!

Paul
 
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DirtDonk

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I'm just wondering if I went to a 1.5" coil and rear leaf spring and stuck with the 7 degree radius arm bushing, if that would make a significant difference?

It might. But then again, you might still have your wandering.
Whether lowering it cures, or even reduces anything depends entirely on what's causing the wandering. And that has yet to be determined.

But lowering the suspension height will indeed increase caster at least a little. And lowering the center of gravity is not a bad thing on the street either.
Just not a guaranteed cure.

Did you come upon your preferred tire pressures based on experimentation? Through even tire tread contact or from how it feels?
And aside from the trackbar bracket then, doing the test and even using your camera like was just described would let you know if anything else is loose.

Paul
 
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buckroseau

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Mar 15, 2017
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Ordered up a set of 1.5" lift springs from Wild horses, got those installed. I had a local suspesnion guy de-arch the springs exactly 1" Just took it for a 10 mile drive at 60 mph, no change, still doing it's random wander. And this is with a 7 degree radius arm bushing.

Attached a couple pics. Pic with the white hard top is before, 2.5" lift, black soft top is now 1.5".

I think at this point I'm going to pull the power steering sector and send it down to west texas offroad and have them rebuild it. Not much else left to check, and figure it can't hurt.

Another question, how many leafs do the rear springs have in a stock leaf pack? The leaf pack I have has 11. The suspension guy made a comment that it seemed like a lot for an older Bronco. And it does ride pretty stiff in the rear end. Just curious.

Thanks.
 

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