C-Bushings, Front pinion alignment and Caster, idea...

[reamer]

Follow my train of thought, is this a derailment or an answer to my problems?

on my'73, with 2.5" lift, I currently have:

** Front pinion pointing down 6 degrees from driveshaft angle. AND
** 0.7 degrees of caster...

This tells me the pinion must go UP, while the knuckles need to go in the opposite direction to pitch the top ball joint "to the rear"

so if I install new 7 degree C-bushings UPSIDE DOWN, this will correct the pinion angle Correct?

Now I can cut the welds at the knuckles-to-tubes and rotate the knuckles 1/8" to get @5 degrees caster....

Rotating 1/8" came from...
Axle tube is 2.75" dia.. this = 8.63" circumference.
8.63"/ 360 (degrees) =0.0239" per degree.
5 x 0.0239 degrees = 11.95 degrees or between 7/64 (0.1094") and 1/8" (0.125")

Thoughts?

 

[Rustytruck]

your not taking in the original 2 degrees of castor nor allowing for the 5 degrees reversing the 7 degrees bushings you have by reversing the 7 degree bushings you are going back 5 degrees more than stock. I would huck the 7 degree bushings and use stock bushings and then rotate the C's your 5 degrees giving you the 7 degrees you want and factory pinion angle. do you have power steering if not the 7 degrees of caster will be brutal. at least that's my math, if trusting my math runs you into the moon its not my fault blame it on Mr.Castro my screwed up math teacher in high school. I am not noted for my math.

 

[jamesroney]

Well, you are BOTH wrong. And it's not bad math. Your math is fine. Your Physics (and associated assumptions) are terrible.

Reamer...as you rotate the pinion UP, the driveshaft "steepness" decreases. So you don't need as much pinion inclination as you think. Rustytruck is correct that the stock 0 degree bushings will be closer to correct. And you left out the necessary additional rotation from the wedge angle. If you want 5 degrees of caster (and you don't) then you need 10.7 degrees of additional caster to pinion angle.

Rustytruck...because Reamer used the "driveline to pinion" angle (delta = 6 degrees) and the measured caster at 0.7 degrees...he is already including the factory 2 degrees of caster into his his delta. It's a horrible way to report the measurement, because he didn't tell us what bushings he has in there TODAY. So in theory, he just needs to make up 6 degrees of pinion rotation from where he is today, AND 6.3 degrees of additional caster to get to 7.

So, based on the completely wrong assumptions, and totally inadequate model...the pinion inclination to caster needs to increase by 13.3 degrees which is closer to .317 inches than to 1/8. (and now we've thrown in inches @ tube radius...another horrid measurement.)

So we are looking at a full derail.

 

[jamesroney]

Follow my train of thought, is this a derailment or an answer to my problems?

on my'73, with 2.5" lift, I currently have:

** Front pinion pointing down 6 degrees from driveshaft angle. AND
** 0.7 degrees of caster...

This tells me the pinion must go UP, while the knuckles need to go in the opposite direction to pitch the top ball joint "to the rear"

so if I install new 7 degree C-bushings UPSIDE DOWN, this will correct the pinion angle Correct?

Now I can cut the welds at the knuckles-to-tubes and rotate the knuckles 1/8" to get @5 degrees caster....

Rotating 1/8" came from...
Axle tube is 2.75" dia.. this = 8.63" circumference.
8.63"/ 360 (degrees) =0.0239" per degree.
5 x 0.0239 degrees = 11.95 degrees or between 7/64 (0.1094") and 1/8" (0.125")

Thoughts?

Oh, and there was also a units fail. 5 degrees x 0.0239 inches/degree = 0.1195 INCHES. (not 11.95 degrees)

 

[Apogee]

Just a thought, but if you're willing to cut and rotate the knuckles, cutting and rotating the wedges isn't really that much more work. I'm mid-process on doing this to a HP D44, and the wedges were way easier to cut loose than the knuckles/C's. Doing this would allow you to set the pinion angle wherever you like with a stock or 2° C-bushing and then do the same with the knuckles just using an angle finder tool rather than a circumferential distance. While not always possible, direct measurements are almost always better than inferential ones in my experience.

Tobin

 

[reamer]

Just a thought, but if you're willing to cut and rotate the knuckles, cutting and rotating the wedges isn't really that much more work. I'm mid-process on doing this to a HP D44, and the wedges were way easier to cut loose than the knuckles/C's. Doing this would allow you to set the pinion angle wherever you like with a stock or 2° C-bushing and then do the same with the knuckles just using an angle finder tool rather than a circumferential distance. While not always possible, direct measurements are almost always better than inferential ones in my experience.

Tobin

What do you mean by "do the same with the knuckles"? Cut and re-weld?

This would be sooo much easier if there were adjustable ball joints out there..

 

[Apogee]

What do you mean by "do the same with the knuckles"? Cut and re-weld?

This would be sooo much easier if there were adjustable ball joints out there..

Yes, cut and weld. This would be so much easier if the front D44's had a little more caster built into them by Dana and nobody lifted their EB's.

 

[Rustytruck]

Well, you are BOTH wrong. And it's not bad math. Your math is fine. Your Physics (and associated assumptions) are terrible.

Reamer...as you rotate the pinion UP, the driveshaft "steepness" decreases. So you don't need as much pinion inclination as you think. Rustytruck is correct that the stock 0 degree bushings will be closer to correct. And you left out the necessary additional rotation from the wedge angle. If you want 5 degrees of caster (and you don't) then you need 10.7 degrees of additional caster to pinion angle.

Rustytruck...because Reamer used the "driveline to pinion" angle (delta = 6 degrees) and the measured caster at 0.7 degrees...he is already including the factory 2 degrees of caster into his his delta. It's a horrible way to report the measurement, because he didn't tell us what bushings he has in there TODAY. So in theory, he just needs to make up 6 degrees of pinion rotation from where he is today, AND 6.3 degrees of additional caster to get to 7.

So, based on the completely wrong assumptions, and totally inadequate model...the pinion inclination to caster needs to increase by 13.3 degrees which is closer to .317 inches than to 1/8. (and now we've thrown in inches @ tube radius...another horrid measurement.)

So we are looking at a full derail.

ok i admit there are better more informed answers. math is never easy. I just know 1+1 makes 3 I learned that from my sex ed class. My math teacher came up with allot of theories why that isnt true. but it still holds true as valid as it ever was. thank you for pointing reamer in the right direction.

 

[reamer]

so much fun. I think I'll tackle this in 2 steps.
1. I'll flip the 4 degree C-bushings upside down, and see if the pinion/driveshaft angles are acceptable, if it is,
2. get new alignment numbers, (caster should be worse) and rotate the knuckles base on new, actual Caster results...

 

[toddz69]

Now you have me curious as to what my pinion/d-shaft angle is. Off the top of my head, 6 degrees doesn't sound that bad for a front driveline.

I'm inferring from your last post that you have 4 degree bushings.

I'm with the others - I wouldn't flip those around. I'd put 2 degree bushings in there, figure out how much you need to rotate the C's and be done with it.

Todd Z.

 

[Rustytruck]

when i was trying to figure it out, It was to put pinion angle back to stock and get the caster needed. but forgot to include pinion angle for his lift so zeroing out the pinion angle back to stock is not technically correct either. I guess that is why people want to do to the 2 degree c-bushings put in backwards? Just have to remember the bushings are designed to give you their degrees in more rather than actual degrees gained. 7 degree bushings are not 7 degrees it is the stock 2 degrees + 5 degrees more to get you to 7.

 

[reamer]

driveshaft and pinion angles "should" be 2 -3 degrees Delta

 

[Yeller]

driveshaft and pinion angles "should" be 2 -3 degrees Delta

Even if you set the pinion at 0 to the drive shaft it will never ride at 0 all the time, it is a moving target as suspension moves up and down, loads change, road camber comes and goes, makes my head hurt....LOL running at 0 technically is not what you want but even if you get there it won't stay there.

I've cut, turned, narrowed and generally reworked way more axles than I want to think about. I always use the theoretical 0 degrees on the driveshaft as a starting point, have never had one be at zero after it was driven around the block. And contrary to what the engineering books say I try to get 7-10 degrees of caster, they have always tracked straight, not had death wobble and tire wear has not been noticeably increased. the low castor angles have always been ford's claim to fame, GM used 7* as the spec on their solid axle trucks, even with leaf springs and no track bar I felt they tracked better.

As for adjustable ball joints, there is an offset bushing for the upper but there is not enough room to make the changes needed to get there, alas cutting and welding is the only option.

I've felt ford engineers smoke crack on front end alignment of solid axle trucks. New Super Duties are a prime example. Their fix for DW is a stronger stabilizer shock, add 2-3* of caster and the problem is resolved properly.

 

[bax]

Cut it all. Cut the outer C's loose. cut the wedges loose. I set up with 4* bushings because they make other bushings to adjust in both directions. I have a build thread in here on a high pinion 44. there are some pictures that may help. For me it was easier to just find the high pinion housing and use it. everything will swap except the gear.