Question on Shackle Angle and Pinion Angle

z06elmo · Apr 19, 2011

Hello,

In the rear I have rubicon express 3.5" full leaf pack and their 1.25" shackle as part of their 4.5" kit. My jeep actually sits closer to 6" lift in the rear. I have an SYE on my NP231 and at current my pinion angle is at about 2-3* pointed down. My shackle angle is almost vertical with the bottom of the shackle pointed slightly towards the front of the car.

Ideally I'd like to have:
1) good shackle angle for better ride and flex
2) Ideal Pinion Angle
3) have the truck not gain any height.

What are the best ways of doing the above?
How does shackle angle affect pinion angle? How does shackle length affect pinion angle? Initial thought i wanted to get a relocation and stock shackle?

Danny

MoparManiac · Apr 19, 2011

If all you do is correct the shackle angle, you won't gain anything in height. Basically keep the bolt that goes through the leaf spring in the same spot, and with a straight line, bring the top bolt down towards the front of the jeep until it hits the angle you want and set it there.

Pinion angle? Ideally fix the shackle angle, cut off the old perches and prep for new ones. Set the axle underneath the jeep with perches resting on the tubes and let the weight of the jeep down on it. Rotate the pinion until 0.5-2º below the output of the t-case and tack the perches in. If you can't weld, use shims underneath the leaf springs to get the angle correct.

z06elmo · Apr 19, 2011

MoparManiac said:
bring the top bolt down towards the front of the jeep until it hits the angle you want and set it there.

Thanks but i don't think i get the part you're discussing here. How do I bring the top bolt down towards the front? Can i re-drill a hole in the current shackle mount?

91to99 · Apr 19, 2011

I think the best bet is to get the HD relocation brackets and a new set of shackles. This way you can dial your lift height in. I run MJ shackles on a worn out set of leaves with an old full length aal and am close to 4 inches.

imtiredzzzz · Apr 19, 2011

I just installed these... http://www.naxja.org/forum/showthread.php?t=955999

Only catch is I had to shorten my shackles in order lower the ride height back down. I also have 3.5" springs and about 4.5" of lift.

94xjstud · Apr 19, 2011

You can always build your own like i did. Made from 1/4 steel welded and bolted to the frame then some 1/4 steel tabs. I added a little lift but with some playing with shackles I'm sure you could figure out a way to do it without getting lift.

No weight on the rear

Weight on the rear and good shackle angle

z06elmo · Apr 19, 2011

thanks for the feedback and pictures. I'm thinking of fabbing my own as well. I'm not sure how good my welder can do 1/4" steel though since it's 110V. Maybe i can do it with multiple passes or bevel the edges pretty good.

Would 3/16 be good enough?

94xjstud · Apr 19, 2011

3/16 should be fine. Another good thing would be to "box" the shackle box with the 3/16

BRIANHO13 · Apr 20, 2011

The kit I sell is already 1/4" and has a ton of adjustability built in......You 110v machine will be plenty to tack them in place.

EricsXJ · Apr 21, 2011

The problem I encountered when trying to guess the change in lift height is the fact that the shackles angled correctly (around 45*) allow the leafs to flatten out at static ride height more than I thought they would.

The change in pinion angle was also a lot more than I anticipated as well. Mine went from a few degrees lower than parrallel to the driveshaft to a few degrees above the driveshaft! To correct that I went from 6* shims to 2.5* shims. I'm sure there is a way to calculate what the change would be if you know all the lengths of the leafs before and after etc, but that is way above my mathematical ability to even try.

bails85 · Apr 21, 2011

i think most of it is trial and error. you never know exactly what is going to happen. especially with springs. hell having a few people with u can change height. even with the shackle adjustments bracket u can buy most guys claim to get about 1 to 11/2 inches of lift out the rear. i just did an 8.8 swap and the tube diameter between the 8.8 and d35 lifted my rear about an inch. now i have to re dial it in because i dont want a stink bug.

z06elmo · Apr 22, 2011

EricsXJ said:
The problem I encountered when trying to guess the change in lift height is the fact that the shackles angled correctly (around 45*) allow the leafs to flatten out at static ride height more than I thought they would.

The change in pinion angle was also a lot more than I anticipated as well. Mine went from a few degrees lower than parrallel to the driveshaft to a few degrees above the driveshaft! To correct that I went from 6* shims to 2.5* shims. I'm sure there is a way to calculate what the change would be if you know all the lengths of the leafs before and after etc, but that is way above my mathematical ability to even try.

Eric - thanks for that feedback. I'm 'hoping' the same will happen with me. I have RE 3.5" full leafs but man they lift the truck a good 5" on their own, and that's with about 5 years and over 50K under their belt.

The resulting pinion angle is also insightful. I'm about 5* pointed down now, so if it goes up 3-4* that would be a welcome thing on my side.

Question on Shackle Angle and Pinion Angle

z06elmo

NAXJA Forum User

MoparManiac

NAXJA Forum User

z06elmo

NAXJA Forum User

91to99

NAXJA Forum User

imtiredzzzz

NAXJA Forum User

94xjstud

NAXJA Forum User

z06elmo

NAXJA Forum User

94xjstud

NAXJA Forum User

BRIANHO13

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EricsXJ

NAXJA Member #616

bails85

NAXJA Forum User

z06elmo

NAXJA Forum User

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