Shackleflip and axle angle

TM1008

New member
21
0
1
Location
Kassel / Germany
Hello everybody.

I have installed a 4 "lift kit on my M1008.
Skyjacker leaf springs at the front and an ORD shackle flip at the back.

but now the angle of the axis or the cardan shaft is no longer correct ... shims must be installed.
but what kind, 4 or 6 or 8 degrees?

Or how can I measure it?

thx for your help
 

Chaski

Active member
673
36
28
Location
Burney/CA
How big of a shackle flip did you go with?

Math explanation.
The Leaf spring is 56" from eye to eye. Lets say you drilled a hole in your driveway and put a pin in it. You placed one eye of the spring on that pin and put a piece of chalk in the other spring eye. Then you used the leaf spring like a giant compass and drew a 112" circle in the driveway.

Pi X diameter = circumference
3.1415 (Pi) X 112" (diameter) = 351.9" circumference.

A circle has 360 degrees

Take 360 degrees and divide that by the circumference (351.9")
360/351.6"= 1.023 degrees per inch

Boils down to about one degree difference per inch you move down your rear leaf eye.

4" shackle flip moves the rear spring eye down 8" (moves your pinion up 8 degrees)
2.5" shackle flip moves the eye down 5" (moves your pinion up 5 degrees)

Many of the folks that use a shackle flip will get a driveshaft with a CV joint at the transfer case, and use small shims to tweak the pinion so it is pointed right at the transfer case. If you don't have a CV at the transfer case you need to point the pinion back down a considerable amount to match angles on both ends of the driveshaft. I have a conventional driveshaft and ORD's 2.5" shackle flip. I made up some 4 degree shims and it is close enough.
 

Sharecropper

Well-known member
Steel Soldiers Supporter
1,424
185
63
Location
Paris KY
I did the 4” shackle flip and 1” zero rates for a total of 5” of lift. No shims whatsoever and no CV at the transfer case. No vibration, smooth as silk.
I really have never “bought into” the theory of matching driveshaft angles top and bottom. In 50 years owned dozens of lifted Chevy trucks and never thought twice about it. It’s just a theory in my mind, because I have never seen any scientific data which says the angles need to be the same. I suggest you run the truck and see how it feels before getting all out of joint in the angles.
Just my 2 cents.
 

Sharecropper

Well-known member
Steel Soldiers Supporter
1,424
185
63
Location
Paris KY

Video from Spicer about driveshaft angles
Well I’ll be dipped. That’s the first time I ever witnessed the “theory”which is now proven. I now see why the angles should match as closely as possible. Maybe the reason my M1028 runs so smooth is because my bottom angle is practically straight due to the axle rotation from the shackle flip. I’ll need to pay attention to the angles and yoke alignment when I order the new driveshaft after my new drivetrain goes in.
Thanks for posting that video. I learned something new after 50 years.
 

Chaski

Active member
673
36
28
Location
Burney/CA
Well I’ll be dipped. That’s the first time I ever witnessed the “theory”which is now proven. I now see why the angles should match as closely as possible. Maybe the reason my M1028 runs so smooth is because my bottom angle is practically straight due to the axle rotation from the shackle flip. I’ll need to pay attention to the angles and yoke alignment when I order the new driveshaft after my new drivetrain goes in.
Thanks for posting that video. I learned something new after 50 years.
Glad you enjoyed the video. One of my buddies has an M1008 with an ORD 4” shackle flip and no pinion angle shims. It does okay on the road. I think it does as well as it does because the pinion is angled up so high that the pinion is pointed above the transfer case. The angles at both ends are not equal and opposite but they are pretty close to equal. At least close enough for government work. This would probably be a total disaster in an M1009 because the driveshaft is so much shorter 72F771B3-712D-4866-88F0-43D0AD38478D.jpegE3F0EC91-E83A-4726-BCC5-FE73309E2117.jpegE3F0EC91-E83A-4726-BCC5-FE73309E2117.jpeg
 

Curtisje

Active member
296
127
43
Location
Twentynine Palms, CA
Glad you enjoyed the video. One of my buddies has an M1008 with an ORD 4” shackle flip and no pinion angle shims. It does okay on the road. I think it does as well as it does because the pinion is angled up so high that the pinion is pointed above the transfer case. The angles at both ends are not equal and opposite but they are pretty close to equal. At least close enough for government work. This would probably be a total disaster in an M1009 because the driveshaft is so much shorter View attachment 805485View attachment 805486View attachment 805486
Damn that looks scary but plenty of dudes run around with worse and never experience any problems. They say the angles should be within 1 degree.

I found this very useful.

 
Last edited:

TM1008

New member
21
0
1
Location
Kassel / Germany
Glad you enjoyed the video. One of my buddies has an M1008 with an ORD 4” shackle flip and no pinion angle shims. It does okay on the road. I think it does as well as it does because the pinion is angled up so high that the pinion is pointed above the transfer case. The angles at both ends are not equal and opposite but they are pretty close to equal. At least close enough for government work. This would probably be a total disaster in an M1009 because the driveshaft is so much shorter View attachment 805485View attachment 805486View attachment 805486

thanks for the video and thanks for the pictures.
It looks the same with my M1008 and I have vibrations while driving.

Found some videos showing where to find the angle.
I'll try it out and then order the right shims

At ORD there are max 6 degrees shims and there is a big difference between 2 and 8 degrees ..... only what's right?
 
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website like our supporting vendors. Their ads help keep Steel Soldiers going. Please consider disabling your ad blockers for the site. Thanks!

I've Disabled AdBlock
No Thanks