Dual Center Pins in Leaf Spring to Relocate Axle

[Yellowsplash]

okay....here goes.

Normally, in about all cases it is recommended to never redrill the leaf spring to relocate the center pin, but I have an idea lingering in my head. I figured I would see what you guys think...

I have a set of Skyjacker 6" lift springs in the rear of my truck along with Belltech Shackles. It appears that with the increase in arch in the spring along with the larger shackle, it has pulled my rear axle forward in the wheel well to the point of decreasing the slip joint travel to a minimum. No catastrophic failure of the output of the transfer case or anything, but it is wearing pinion bearings at an accelerated rate (atleast what I feel has to be the problem). Shop who rebuilt it previously thought pinion angle was culprit, but it is fine. With having to rebuild the diff a third time soon (averaging 10K miles per rebuild), this has to be addressed.



Both pics are with full weight on rear axle...you can see how the axle is positioned closer to the front of the vehicle.



My thoughts are to redrill the leaf spring two inches behind current center pin and run dual center/alignment pins just like the newer F150s. From the info I have researched, as long as the points of the spring which are drilled are supported between the perch and u-bolt plate, it doesnt allow flex in that region of the spring, therefore, not creating a weak spot as redrilling normally would. This would offset the axle between 1-2" while still keeping a center pin the original hole, and help secure the axle to the spring much better. And of course would require me to redrill my perch and spring plates to accommodate the modification.

Pic of an f150 raptor leaf spring

What do you guys think?

 

[Sasquatch_Ryda]

What about a zero rate add a leaf block that will allow you to move the axle without re-drilling anything?

And I'm really not thinking this is causing pinion bearing issues....

 

[Yellowsplash]

I thought about a zero rate, but I'm trying to avoid a block and/or lifting it any higher than it already is. Any increase in leverage to promote axle wrap makes me cringe. I suppose it is an option, just trying to think outside the box for a solution.

As far as the driveshaft...if there is not enough play in the slip yoke and it bottoms out, that energy from the suspension cycling requiring the driveshaft to shorten/lenghen is going to apply pressure somewhere. Some to the transmission mount which has some play, and the other to the pinion, specifically the outer bearing. Similar to the leveraging effect high offset wheels have on the TTB wheel bearings.

 

[PlumCrazy]

I drilled new holes in my perch an U-Bolt plate to shift my axle forward 1.5"

No Issues in the last 3 yrs

 

[baddis]

what about turning the springs around?

 

[Yellowsplash]

what about turning the springs around?

I think that would offset the axle too far and the driveshaft would be too short. Im only trying to gain 1-2". That would probably net over 4" of change. As far as I know, the slip yoke only has 3" of travel.

 

[PlumCrazy]

I had the opposite issue though. My Chevy lift leaves pushed my axle too far back.

Here are a few pics from way back when I did it. In these pictures I still had a stock block, so I drilled the a hole for the center pin in the top of the block, not the perch

Then later I lowered the truck back down a few inches with softer coils and a new radius arm setup, so I swapped the stock block for a 3/4" solid block I made. I drilled and tapped them to add a centered bolt for the perch, then an offset hole for the actual leave pack center bolt.

So I guess looking back.. I lied. I didn't drill offset holes I the perch because them my block would be half off the perch, but if you don't need a block, you could just drill the perch and U-Bolt plate. (Like the Ruff Stuff 8.8 swap kit)

 

[PlumCrazy]

The other thing to think about is what happens when you load the truck down and the springs flatten out....then your wheels will be too far back. It may look odd with at ride height, but as the springs flatten, the wheel will go further back, so if you move it back, you may run into issues.

 

[Yellowsplash]

Thanks for the info and pics to better illustrate it. I suppose running the extra center pin isn't necessary, just a thought to better secure everything together with the offset in mind.

I have ballistic fabrication u-bolts and their spring plate which is drilled for 1" offset in both directions, but im using the factory perches that came on the exploder 8.8, just cut and rewelded. I suppose I could get away drilling an offset hole 1.5-2" on the perch. Hard part would be drilling through the 3/8" ballistic fabrication spring plates in the proper offset. Don't believe the 1" hole would be enough offset to center the axle.

The other thing to think about is what happens when you load the truck down and the springs flatten out....then your wheels will be too far back. It may look odd with at ride height, but as the springs flatten, the wheel will go further back, so if you move it back, you may run into issues.

I don't normally haul all that much. Being my truck is a stepside, the bed is lighter due to outer fiberglass design. I primarily want to center the axle in the wheel well as it is pulled toward the front now even at normal ride height. Once centered, I don't believe I'll run into any issues. Similar to what youve done, just in the opposite direction.

 

[PlumCrazy]

I planned on making new U Bolt plates out of 1/2" plate, but as you can see, I still haven't.

Drilling a hole in spring steel isn't going to happen even if you had tried.lol You would have to have a spring shop heat it up and punch them out, but chances are the spring would snap in half at the hole over time.

 

[Yellowsplash]

I had planned on having a spring shop do it, not try to drill it myself. I know they made a buddy of mine a spring pack for a newer F150, again with two center pins.

The plan was to keep the old center pin intact. Usually the failure occurs when the old pin/bolt is taken out and the hole is moved outside from the u-bolt clamp load where it is subject to actively changing pressure at the now weak failure prone point. Think of continuously bending aluminum till it breaks. If kept under pressure from both bolt/pins and under u-bolt pressure between spring plate and perch, would it not work?

If dual center pins work for a larger truck, why won't it work for a Ranger?

Just a new idea I thought I'd throw out there. I believe I'm gonna try to just drill the perch and spring plate alone to see if it will allow enough offset.

 

[FritzTKatt]

If you put a new hole in the plate, to offset that while keeping the same u-bolt location, and add like 3/8 or 1/2 plate between the block and spring that has an offset hole on one end, and a nipple/stud on the other side, then wouldn't that allow you to achieve the offset you need? As well as avoiding truly lifting the truck any more, nor would it touch the spring.

Ever think to check your pinion angle? Might be time for a carrier drop mod, 1 piece, or at least some shims.

 

[Yellowsplash]

That is what a zero-rate essentially is.

Pinion angle was set by me when I welded the perches on during the exploder 8.8 swap. I know it is correct. I didnt start having trouble till after I decided to ditch the block and install the Skyjacker Leafs. And I have been running the 1-piece driveshaft for nearly 10 years. Been at it for a while...

 

[bobbywalter]

dual pin springs are likely different steel then what you have and dimension specific....



if your pinion angle is truly perfect....leave it alone....put traction bars of some sort on it. your springs wont make it with two holes that close together.


just drill a new hole in the perch and put it there if you really want to..


moving it back will just smash the fender if it can actually use the spring and will pull the slip apart if it is already marginal... you should consider the long travel slip with this setup regardless..


i regularly bust springs and suspect a few issues with your setup. have someone brake torque the rig(not tire frying just to the point though..) and measure the movement of the pinion under load. if i have to tell you to be careful and why....then sell it and ride a bike(that is not for you).


when i run my soft springs i get vibes at 80 ish mph because the pinion rolls up so far....this is not pulling a trailer...just 37 in tires....at the same driveshaft rpms with 33's it dont happen....and it does not reoccur at any speed. with 35's it happens though.


setting pinion angle theoretical and what is really needed are not always the same thing.

in this case you have a radical arch spring and working swing arm angle as a result of eliminating the block.....to hopefully avoid axlewrap....but.....

when you determined the pinion angle was it after fully cycling the rear axle with just the main spring? that usually changes stuff from just static ride height after watching how it works. its not too critical usually till you get over 5 inches..

my current springs allow my axle to rotate up a little over 1 inch at cruise speed from rest unloaded. i made a tool that bolted to the cover and pulled o rings down a shaft because my ol lady would not let me use her camera before...

if i have to raise the truck anymore i will go to hd 150 2wd springs and lower the hangers a bit.....huge arch springs are a pia to work with unless they are big money units. usually though they work pretty good with few issues.


a cursory load test should be indicative....a center mount traction bar on a shackle may be ideal here. only take a second to check.

 

[PlumCrazy]

I forgot to mention...I added a single traction bar with a shackle. My springs were super soft and had a HUGE arch. so my rear U joint would actually bind under semi aggressive acceleration.