C-Bushing with radius arm drop down brackets

[capt2130]

Have a 72 with 3-1/2 lift. Looking at the existing bushings they appear to be original. I realize it`ll need to go to an alignment shop to be checked. I have new 7 degree. But I`m wondering if that would be to much since the arms are currently dropped. Anyone know what the correct angle is needed to get it close? - 2, 4, 7 degree???

 

[rguest3]

Interesting it would still have original bushings with the Drop Bracket added?

I do like a little extra Castor but I think the 7* would be too much with the drop Brackets.

See what the Castor is from the alignment shop.

 

[Broncobowsher]

How far are the arms dropped. If it is also 3½" then the caster angles are all back to stock. If it is a 2" drop, the caster correction needed will be as if (3½ lift - 2" caster correction =) 1½" lift.

 

[capt2130]

It looks to be 3-1/2. I`ll verfify this evening. If that`s the case, stock or 2 degree should be good starting point. Being that the bushing are so worn. I think it would be useless to check and see where the caster is now. I would like something solid to start from. Even tho it could be more time and parts.

 

[capt2130]

The drop brackets have 4" drop. Appear to be WH 1605. It doesn't drive to bad. But the bump steer needs to improve. Thinking 2 degree??

 

[Broncobowsher]

2° would be a little extra caster. Good for a Bronco. So long as the front driveshaft U-joint doesn't bind.

Bumpsteer is a drag link and track bar issue.

 

[DirtDonk]

Have you posted up pics of your front end and steering linkage yet? Be good to see what you're working with.

Paul

 

[capt2130]

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[DirtDonk]

Great looking rig!

And yep, stock rubber bushings. Don't see many any more, but they're still out there just like yours.
You have a totally custom upper trackbar bracket that was used to lower the bar. You need to raise it back up into one of the other holes. I'd say just the very next hole or two would do the job, but I can't see them for sure from these angles.
You can tell though, once you remove the bolt and start moving the upper end of the bar around you can see when it becomes parallel with the drag link.

Stock steering was very good for a vehicle this size in it's day, but with your larger tires and much more offset wheels (wider overall and more negative offset, which pushes them outward) puts more leverage against the tie-rod and drag-link which makes them flex more. Not a huge thing, but when added to other things it can make little issues larger.

Can you take another pic or three of the backside of the front end to look at the pinion angle? We can maybe tell visually if you're nearing the limit of travel for the u-joint, or have more room to move with C-bushings.
Normally you have more than enough for 6 degrees, which is what you'd have with the 4 degree drop brackets and 2 degree bushings, but add the lift to the equation and it starts to get close.
Luckily you don't really see issues on the street, but taking it off road and working in four-wheel drive is when bad things crop up.
You might be perfectly fine though. Every Bronco is different.

Over all it looks like the previous owners paid a lot of attention to details. Looks very nice, and for now very nicely done too.

Paul
The

 

[Broncobowsher]

I see multiple holes in the track bar drop bracket. And the angles look a little off as well. I think that raising the track bar by 1 (maybe 2, but doubt that much) holes should tame down some bump steer.

That track bar drop bracket is HUGE. Don't normally see them that tall. I think this Bronco has had a lot more lift in the past and it has been lowered to a more manageable height. That drop bracket looks welded on, generally good. But the height puts a lot of stress on the frame. I would inspect the frame at the top of that drop bracket, look for cracks.

 

[DirtDonk]

Nevermind. I looked again and can see the pinion in the darker light. It looks fine, so I don't think you'll have any issues with the added caster from the C-bushings.

So two things to do before then. As mentioned get it checked so you have a printout of your current settings (and while on the rack they can tweak the toe-in if needed) and do "the test" with the help of a friendly assistant.

With the tires on the ground, have the helper turn the steering wheel back and forth enough to twist the front end. About half a turn in each direction is usually enough.
While they're doing this continuously you are watching everything underneath. In addition to the normal things like steering linkages, you will want to pay particular attention to the radius arm drop brackets. If they appear solid and tight, you don't have any additional worries. But if they are flexy and twist a lot, this is not good for your road manners and will lead to all sorts of wandering and such.

Same for the trackbar. With that long bracket and the bar in it's current setting, you could have excess flex. And a flexy trackbar mount really makes a Bronco wander!
Look for any slight movement not only in the bracket where it's mounted to the frame, but the lower bolt and bushings as well. And the steering box where it's bolted to the frame, and the tie-rod and drag-link ends.
Any movement side-to-side play is bad and needs to be addressed.

While the (at this point, very paitent!) helper is turning the wheel, you can also check the rear springs and such to see if anything is loose there as well.
This whole thing takes maybe five or six minutes, but once you've done it a couple of times you can do it in under a minute because you know everything you're looking for.

This test will even showcase loose wheel bearings. Watch the wheels and brake drums, as they relate to the brake backing plates (or the similar disc brake parts) to see if they move independently of one another. If you're not sure you can often put your fingers between the wheel band kunckle, to see if you feel movement.
Some movement could be wheel flex, but most will be bearing and ball-joint play.

Good luck. Have fun!
At least there are some obvious things you can do based on the pics.

Paul

 

[capt2130]

Thanks guys! Yes I agree there may have been a taller lift on it at one time. PO didn't do it or know much about it. He didn't have it long.

Angles on the front drive shaft check 10 degree. What is recommended angle to shoot for?

I moved the track bar up two holes and made it parallel with the drag link. I did check a while back with someone turning the wheel and everything seemed tight. But I need to do it again. The track bar drop is welded and I didn't see any cracks. The welds definitely aren't that desirable. I'll probably grind it out and lay a cleaner weld or fab up something different.

I'll get it to a shop and have them check out the caster and move form there.

 

[DirtDonk]

Angles on the front drive shaft check 10 degree. What is recommended angle to shoot for?

It's not so much the angle of the driveshaft we are concerned with (though ultimate that matters too) regarding changing the angle of the pinion. It's the relationship angle between the pinion shaft and the driveshaft. In other words, the working angle of the front u-joint.
If you just keep tilting the axle back at the top, eventually the u-joint will be in a bind.

At some point, the upper CV section can bind too of course, but I don't remember what that working angle is. Maybe 25 degrees?
The front u-joint max working angle is somewhat less if I remember. Maybe 15 degrees? Others will know.

Basically if it was all adjustable and we set it up however we want, the front u-joint would be working at just a slight offset from the centerline of the driveshaft. Not much, but not zero either. Just enough to keep the u-joint working and lubricated and working, but not so much it weakens it too much.
Any cardan style joint like we have, whether it's a single-cardan like at the differentials, or a double-cardan like at the transfer case, gets progressively weaker as the angle increases. After a few degrees it increases a LOT.
Which is why, when in four-wheel drive, you NEVER get on the gas hard with your front wheels turned tight. Or at least keep it in the back of your mind as you're trying to get unstuck or over an obstacle.
Many a front joint and axle shaft have given their all under those conditions.

But for this discussion we were talking more about binding and vibration than actual failure points.
If your driveshaft is 10° down and your front pinion is 9° up (offset of 1 degree) then you can add more C-bushing no problem. Adding the full 7 would put you at 8 degrees or so. I say "or so" because the pinion is not in the centerline of the axle shafts, which is what the C-bushings are acting upon. I don't think I've ever read where anyone has actually calculated, or measured the degree change of the pinion when compared to the axle housing.
Alternately, if it's 10 down for the driveshaft and 20 down for the pinion, meaning it's another 19 extra degrees in the wrong direction, you're running up against a limit of the u-joint's ability to spin. And long before that, you'd have at least felt a vibration when in four-wheel drive.
They're just not able to work efficiently at those higher angles.

Yours looks to be pretty close to zero, but pictures lie when it comes to angles and perspective. If you can measure the angle on the pinion, then you'd know for sure. Some kind of straight-edge on the yoke, like a framing square, would do the trick.

Paul

 

[capt2130]

Sorry I should of said I calculated the drive shaft at 10 degrees. It’s actually 18 degrees with the pinion angle at 8 degrees.


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[DirtDonk]

Ahh, good. So I'd say while 8 degrees is still within the tolerable range by a bit, I would not want to add another 7 to that.
Here's where having your caster checked gives you another tool in your arsenal.

If you know what you have now, with the drop brackets and zero offset bushings, you can calculate what you might need still for best street handling (3 to 6 degrees positive is nice, at least 4 is even better) and see if that falls within the range of the u-joint's happiness.
If you can get away with 2 degree C-bushings then, fantastic. If not, then it could be on to Plan-B next.

Paul

 

[capt2130]

I did some rough measuring and it looks to be 0 degrees. Could that be right? That would explain the not so good handling.

I’m looking at it two ways. Either go with 2 or 4 degrees bushings. Or cut the drop brackets off and use the 7 degree bushing that I have and then I’ll have extra clearance. What’s your thoughts?

 

[DirtDonk]

Still have options.
Losing the drop brackets is actually not a bad thing from most aspects. They hang down low and lose ground clearance, which might not be pertinent to a road-going Bronco. But they add flex too (even on the street) and so that's not a good thing anywhere.
Losing 4° from the drop brackets puts you at a theoretical negative 4, while adding 7 puts you at a theoretical positive 3. That's just a minimum for a power steering equipped Bronco, but it is in the range of good handling. Most of us are happy to achieve 3!

In theory too, your moderate angle between the pinion and driveshaft means that 7 degree bushings should not overly tax your front u-joint when in 4wd. But here again, it's theoretical until you do it and can actually measure things.

The negative side of losing the drop brackets is that, with the lifted springs, your front axle/radius arm setup will be tilted more forward at the top. This gives the coil springs a little outward bow, puts some bind on the trackbar mounts (unless you have an adjustable trackbar, in which case you can tune that out) and puts a slightly unnatural bind on the rear radius arm bushings. This last is usually not an issue either, but theoretically will shorten the life of the bushings.
Some people experience wear and tear on the bushings this way, while others never have a problem. Mine are the original rubber from '71 still!
Once again, we see that "every Bronco is different" but only sometimes!

Because the brackets are welded and you can do C-bushings relatively easily in the driveway, there is another option. It's not quite as good perhaps, and could be considered an experiment. You could add 4° C-bushings now and see how that improves your street manners. It's the same gain in degrees of caster (plus one extra degree) as the previous discussion, but can be done quickly and relatively cheaply.
If it improves things you can plan your next move. You might leave it alone if it's fixed enough, or you might decide to go ahead and change out the drop brackets after all.

It's just a suggestion though. Even with the negative aspects of losing the drop brackets, I think the positives outweigh them and that's the way I'd personally go. Lose the brackets and go with the full 7 degree bushings. You should still have enough room in your u-joint travel to live long and prosper under there.

Just so you know, ultimately the "correct" way to do all this is not to add different Band-Aid parts, but is the cut-n-turn method.
That's where you leave the radius arm brackets stock (less flex and more ground clearance), put in the minimum C-bushing in polyurethane (2 degrees in this case to keep the pinion angle modest) and turn the outer steering yokes (c-shaped part at the end of the axle tube where the ball joints are) to achieve proper caster.
Takes more time, and most people don't have the desire, or the equipment to cut through the big weld and then re-weld it once it's corrected. But it's the proper way to do this for most of us.

Didn't mean to add more confusing information, but figured you should know all the options open to you, and some of the reasons for doing one or the other.

Paul

 

[DirtDonk]

I did some rough measuring and it looks to be 0 degrees. Could that be right? That would explain the not so good handling.

To touch on this, yes it absolutely could be right. Still better to put it on an alignment rack to get the detailed info, but if your measuring methods are correct there is no reason to suspect them.
It's extremely easy to achieve zero or even a negative number with caster on a lifted Bronco.
The earlier years had less caster to begin with as with manual steering it's easy to have too much caster. Makes it harder to steer. So Broncos were designed with less, and got even less when it came to the rough production accuracy at Dana those years. Apparently there jigs shifted a lot, or they did not even bother because most EB's seem to have come from the factory with less than specified caster angles. Once you lift it then, even those low numbers go out the window.
It's not uncommon then to have zero or less, even with 7 degree bushings!

For those people cutting and turning is the only option. You can't logically add both 4 degree drops and 7 degree bushings because most pinion angles will then be so bad that the driveshaft might not even turn without binding even at ride height. Add suspension cycling up and down to that, and breaking a u-joint or yoke is not out of the question.

Hence the need to know the actual caster. If yours was a good method, there's no reason to think that your zero degrees is not accurate.

Paul

 

[capt2130]

I'm pretty confident of the measurements. Think cutting the drop brackets is the best way to go as well. I have everything to do it here or at my shop.

I know power steering was added in 08 from the documentation. The pitman has a drop of 5" roughly. Need to actually take it off and check with a height gauge. Will that need to changed to something less?

I also have new 3-1/2 WH lift with Bilstein's I could replace the entire lift with. I had intentions to put it on my 76 and make it a LUBR but not sure I want to change the originality of it.

Sorry my list of things keeps changing and growing!

 

[Broncobowsher]

If you are taking the drop radius arm brackets off, the answer is easy. Get the 7° bushings.

Unless....
You just know you want to do it right and do a cut and turn of the knuckles. In which case I would say get the 2° for better driveshaft angles.