Knuckle grind and turn...UPDATED progress

[Dan74Bronc]

I need a second opinoin and a sanity check before I weld this back together.

I ground the weld off of the knuckle to the axle tube and am turning the knuckle back 9 degrees to correct castor and driveline angle. I have a 5 inch lift, TRO steering and death wobble. Right now there is 7 degree C-bushings in it. I thought about extended radius arms, may still do that, but I think this is a better idea.

So my thinking is rotate the knuckle back 9 degrees and go back with 2 degree or even stock C-bushings. I'm shooting for about 5 degrees castor but need a sanity check on my cipherin'. I marked the end of the axle tube and the knuckle with a chisel before I started for reference. In the third pic you can see I moved it about 1/8th of an inch so far. I figure I need to go .2146".
Here's my math; axle tube O.D. at knuckle is 2.732" so the circumfrence is 8.5828". 9 degrees of that is .2146" (8.5828/360x9). Heat it, pound it 'til the marks are that far apart.
Am I way off base here?

I did a search but only saw the one post by Lars about 5 years ago, surely someone has done this since then.

 

[Tito]

Thats about the only article I have seen on here either. Most people just go to long arms and 7* bushings. Looks like you are on the right track though!

 

[onebadd73]

I'm thinking about doing the same thing only paying someone to do it. A local shop quoted me $ 150.00 to rotate the C's.

 

[crawln68]

I did mine on my front D60. I posted the pics on here, so they should come up in a search, but if not I can repost them if you want. The tops of the D60 knuckles are flat, so just put an angle finder on each side and rotated them back to 7 degrees of caster. The first one is easy, but the hard part is making the opposite side match. You'll see what I mean when you get there. Good job on the grinding though. I can see the crack around the tube so you got all of the way through the weld. Looks good!

 

[Dan74Bronc]

150 bucks isn't bad at all. I've got about 2 hours invested in one side so far. I'm just not sure how far to turn it.

 

[Dan74Bronc]

The first one is easy, but the hard part is making the opposite side match. You'll see what I mean when you get there.

Yea, I've been thinking about that. I'm concerned that my angle finder may not be accurate enough for that purpose. I guess I'll burn that bridge when I get to it.

 

[broncomaster]

I'm thinking about doing the same thing only paying someone to do it. A local shop quoted me $ 150.00 to rotate the C's.

This will correct the caster but make the drive line angle worse. Cutting and rotating the ends does not change drive line angles.

 

[crawln68]

This will correct the caster but make the drive line angle worse. Cutting and rotating the ends does not change drive line angles.

Actually, it does both. That's the beauty of doing this. You can rotate the C's back to correct the caster and rotate your pinion up all at the same time.

 

[Apogee]

Actually, it does both. That's the beauty of doing this. You can rotate the C's back to correct the caster and rotate your pinion up all at the same time.

X2...two birds with one stone.

As for the math, it all looks good to me. I would position your pinion angle first so that's where you want it and then figure out what caster you want to run from that baseline. If you ever plan to run aftermarket extended radius arms, keep in mind that most have about 4.25 degrees of caster correction already built into them...you could always runs some 2 degree bushings backwards to cancel it out if you had to I guess.

Nice work on the knuckles so far.

 

[bludorbronc]

What about c bushing mount on axle housing, don't they have to be moved also to correct pinion angle? Or are you going to use degreed c bushings to correct pinion angle and adjust caster with turning knuckle?

 

[Dan74Bronc]

What about c bushing mount on axle housing, don't they have to be moved also to correct pinion angle? Or are you going to use degreed c bushings to correct pinion angle and adjust caster with turning knuckle?

We'll that's the plan. Rotate the knuckles back then put stock or 2* c bushings back in to rotate the pinion back up. I'll post some pics as I make progress. May not be today, My oldest son has a football game and the middle boy has baseball today.

 

[bludorbronc]

After going to all that work I would hate to say" I wish I would have turned them further". If I was thinking about going to extended arms, I think I would buy a set and install them and the axle housing with springs and axle on jack stands to get a real measurement on pinion angle, so I would know if there is a bushing available to correct it. Then with a digital level you could set caster accurately. And if you need to cut off bushing mounts instead it is eay to do, cut them off,mount back in radius arm, set pinion angle,tack in place, take arms off and weld in place.

 

[toddz69]

I need a second opinoin and a sanity check before I weld this back together.

I ground the weld off of the knuckle to the axle tube and am turning the knuckle back 9 degrees to correct castor and driveline angle. I have a 5 inch lift, TRO steering and death wobble. Right now there is 7 degree C-bushings in it. I thought about extended radius arms, may still do that, but I think this is a better idea.

So my thinking is rotate the knuckle back 9 degrees and go back with 2 degree or even stock C-bushings. I'm shooting for about 5 degrees castor but need a sanity check on my cipherin'. I marked the end of the axle tube and the knuckle with a chisel before I started for reference. In the third pic you can see I moved it about 1/8th of an inch so far. I figure I need to go .2146".
Here's my math; axle tube O.D. at knuckle is 2.732" so the circumfrence is 8.5828". 9 degrees of that is .2146" (8.5828/360x9). Heat it, pound it 'til the marks are that far apart.
Am I way off base here?

I did a search but only saw the one post by Lars about 5 years ago, surely someone has done this since then.

Dan:

You're on the right track. 9 deg. sounds like a good number to shoot for. I just finished bolting mine all back together after having it done to my axle. Took it on the first road trip today and I could tell just by the steering feel that I had more caster. I had mine rotated 8 deg. I was running 7 deg. bushings for years and the alignment shop said I only had 2-2.5 deg. positive caster (with about a 3" lift). So I pulled mine out and had Blake Machine in downtown Phoenix do it (they did Airman's a few years ago). I've gone back to 2 deg. bushings and I think I'll have about 5-5.5 deg. of caster now (according to my cheapie angle finder) and I should get about 1 more degree once I bolt Lars' long arms on. I want to be in about the 6 deg. range; the lower end of the 78-79 caster spec.

$150 sounds dirt cheap to rotate the C's. I paid almost 3 times that for mine and it took them 3 weeks longer than they originally said it would take, and they rotated one side too much the first time too :-(. I must say though - it's damn impressive to walk into a machine shop and see your whole front axle chucked up in a lathe!

Todd Z.

 

[rjlougee]

and they rotated one side too much the first time too :-(. Todd Z.

Todd, what did they have to say when you took it back to them?
Joe

 

[toddz69]

Todd, what did they have to say when you took it back to them?
Joe

Well, at first they did the typical, "well it was right when we checked it here"...blah...blah....blah... I didn't immediately fire back (although I wanted to) but I did have the foresight to bring my angle finder along and I said, "let's check things". So he got out his and I got mine and we both measured and he agreed one was about 2.5 deg. off. The owner was very apologetic when I picked it up last Thursday and even gave me a few $$ back. I double-checked things BEFORE I left the shop this time and they nailed it the second time.

Drove it on its first trip yesterday and I can tell I have more caster. Better on-center feel, less twitchy on the highway, and better return-to-center action with the wheel. I'll be interested to see what the alignment shop says the caster is vs. what I measure with my angle finder.

Todd Z.

 

[Dan74Bronc]

Thanks Todd, That's just what I needed, real world data to go by. I'm going with 9*. I'll post pics as I make progress, hopefully later in the week.
Dan.

 

[airman]

I went with 8 degrees when I did mine. But I also have dropped rear arm mounts and 5.5" lift. I think you will like the 9*. I'm going to do driver side ball joints sometime this week so I will have one side stripped down if you need a look.

 

[Dan74Bronc]

I went with 8 degrees when I did mine. But I also have dropped rear arm mounts and 5.5" lift. I think you will like the 9*. I'm going to do driver side ball joints sometime this week so I will have one side stripped down if you need a look.

Just a few questions if you don't mind. How far did you drop your mounts, and what C-bushings did you put back in. Although it may be too late to ask since I just ordered a set of 2* bushings and some 4.5" rock crawler coils from WH.

When you get it apart I would like to take a look. I'm off work Tue thru Sat this week. You can PM please.

Thanks, Dan

 

[onebadd73]

What would be a good # of positive caster to shoot for with my current set up? I have 5.5 springs, cage arms, and I'm running a FW HP dana 44. I have the housing down to nothing and I'm currently waiting for the master ring and pinion install kit. I called Bronco Alley here in So.Cal and Tim quoted me $150.00. Just not sure what # of positive caster I should ask for, since I know the cage arms have some positive castor built in them.

 

[lars]

Here's how I did mine a few years back: http://www.broncofix.com/viewtopic.php?t=2842
I wouldn't use the carbon air arc gouger if I was doing it again; a cutoff wheel in an angle grinder is faster and much less messy.

As noted in that thread, I got 5 degrees of caster, which helped a lot. When I installed my home-made extended radius arms last year I picked up another degree, which helped even more. Makes long freeway trips way more relaxing.

The mod is a lot of work, but it solves a lot of problems and makes your Bronco happy.