Pinion Angle

[DirtDonk]

The driveshaft (pic #2) is pretty straightforward. So we're good there.
The pinion shaft however (pic #1) is harder to dial in with the way you did it. You can still get pretty close by eyeballing your angle finder square to the centerline, but I think an angle/square thingy (carpenter's square?) would be ideal. With a small square you can lay it on the flat surface of the yoke (at the u-joint end) which would be 90 degrees to the angle you want to measure, but laying your angle-finder on the opposite beam of the square would get you into the same plane as the driveshaft.

If your current figures are correct, you are 14.3° off from parallel. You want 1-2 degrees, so you'd have to correct the pinion angle about 12-13 degrees up. Meaning you'd need about a 9 or 10 degree axle shim I think.
I never have memorized the geometry calculations needed to figure out what a change at the spring perch nets you at the pinion, but others here have figured it out.

I'm going to go read Steve's texts again to see if I'm missing something too. I've found some of the Ford writings to be unclear about what they're trying to help you achieve, but in theory everything we need to know is buried in his pages. I just need to figure out how to interpret them.

But see if you have a carpenter's square laying around somewhere you can use on that pinion to verify your existing measurements.

Paul

 

[blubuckaroo]

I don't understand so much heartburn over the rear pinion angle but none for the front pinion angle.?:?

 

[DirtDonk]

Ok, I re-read it again Steve, and I don't see any pertinent information to this discussion. Is it there and I'm just not seeing it? Is there another page that I need to forward to, in order to get to the double-cardan section and how to measure and set up a double cardan shaft?
It does mention them 2/3 of the way down the text, but only in relation to the maximum working angle of the u-joints. It even references a tool like SSDD is now using, but nothing about how to measure the angles accurately.
Again, unless I just missed it.

Let us know.

Paul

 

[SSDDBRONCO]

Ok so I went ahead and corrected the pinion angle. Pretty sure I did it right this time if I’m understanding and following DirkDonk’s instructions.

Driveshaft angle: 26.5
Pinion angle: 15.6

I also used the Tom Wood’s driveshaft calculator and it told me I would need a 6 degree shim. Not sure how accurate the calculator is?

https://4xshaft.com/blogs/general-tech-info-articles/slopes-vs-angles

 

[DirtDonk]

It's close enough to my previous "assumption" that if you're off by 9-10 degrees (you're at a high-10) then a 6 degree shim has proven to be the ticket.
Which falls in line with what 98% of suspension lift installations end up needing when the pinion angle is off.
That's why we only carry a 6 degree shim. Because it's been just the right amount to properly correct rear pinion angle issues. So far...
Even got lucky with a friend's '76 that had the wrong pinion angle from the factory! Or if it was not from the factory (we'll likely never know) it happened when his entire rear end housing was warrantied at the dealer not long after he bought the truck.
That one was just blind luck that our 6 degree shim took care of it. But it's by design that it works with our lift kits.

Thanks for the link to the Wood's calculator. I did not know they had that. Going to check it out after this.

Paul

 

[SSDDBRONCO]

It's close enough to my previous "assumption" that if you're off by 9-10 degrees (you're at a high-10) then a 6 degree shim has proven to be the ticket.
Which falls in line with what 98% of suspension lift installations end up needing when the pinion angle is off.
That's why we only carry a 6 degree shim. Because it's been just the right amount to properly correct rear pinion angle issues. So far...
Even got lucky with a friend's '76 that had the wrong pinion angle from the factory! Or if it was not from the factory (we'll likely never know) it happened when his entire rear end housing was warrantied at the dealer not long after he bought the truck.
That one was just blind luck that our 6 degree shim took care of it. But it's by design that it works with our lift kits.

Thanks for the link to the Wood's calculator. I did not know they had that. Going to check it out after this.

Paul

Perfect. Looks like I’ll be purchasing the shim from you guys soon. Thanks for all the help.

 

[bmc69]

I don't understand so much heartburn over the rear pinion angle but none for the front pinion angle.?:?

That one's always hard to get "right" with any lift. :-X Have to cut loose the outer Cs and wedges to keep necessary caster while rotating the pinion up..

But fortunately, I almost never run at any speed with 4wd engaged. Most don't.

 

[jamesroney]

I don't understand so much heartburn over the rear pinion angle but none for the front pinion angle.?:?

I love this question!

So many people just accept the compromise and don't care. But if you want the correct caster, and the correct pinion angle, and the correct wedge angle...you have to cut and turn the inner c's and re-index the wedges.

It turns out that a single 1310 Cardan universal joint will run out of phase and at high angle...it just vibrates and wears out. Since 99% of the time the front driveshaft is disconnected...most people don't care. That and the fact that the Dana 20 transfer case drops the front output by 5 inches. Lastly, the front axle controls pinion angle thru the radius arms. So you don't get as much axle wrap, and U-joint bind.

I just did this HP 44 yesterday. Cut and rotated inner c's and wedges. For a High Pinion, the pinion angle for 3.5 suspension lift and Dana 20 is 7 degrees. This axle is also getting 7 degrees of caster, for a total of 14 degrees.

 

[Steve83]

If you post ALL your readings, we can check you.