double_0_7

I have the axle out. I'm doing the brake conversion and going leaf under axle because I want to lower. I'm installing a 3" lift shock so it will only be dropped a little.

I posted this on another thread I'm a member of, and was hoping I might be able to get some input from you guys too.


Also, over there, I got the following as response, and I'm really wondering if I'm in over my head. Can anyone give a little input.

TRCM

OK, what are you doing ?? or trying to do ??

1) You say you want to go axle under, but the axle in the pics is already made to go under the springs, so I am not sure what you really mean

2) Using a 3" lift shock means the shock will be 3" longer compressed, and 6" longer extended, so it will not lower anything or even work on a lowered axle without some major re-engineering

3) or do you mean you are installing a 3" lift KIT instead ???

If you want to lower your vehicle like I think you are saying, you will be going spring under, which means the spring is under the axle, and yes, you will need to move the spring perch to the bottom of the axle tube, or just weld another on the bottom (no need to remove the top one), but the shock bracket will have to move, and it could be moved slightly inboard and still work ok, and keep the same shocks. The shock mount needs to be below the centerline of the axle tho, or you will lose the axle wrap fighting benefits of the lower location (not much benefit tho)

I would not re-use the spring perch,but instead weld on a new one...you'll loose a good bit of the perch cutting it off, and it may make it harder to weld back on correctly, and you want both sides to be the same in angle relstioonal to the pinion, as well as distance from the centerline of the axle (height off the tube) so the axle doesn't sit crooked). New perches are just easier to do.

Shock mounts aren't as critical but still should be as close to the same as possible but on opposite sides of the axle to fight axle wrap.

You will have to figure pinon angles once you have everything mocked up and in place (but not yet welded), so you can rotate the axle as needed to get the right numbers.

You will also now be very close to the axle hitting the frame & fuel tank, exhaust, etc under compression, so you will have to address that as well. You will probably be moving the axle up close to 7" by doing this, so clearance will get tight under there, not to mention the wheels/rims and the body.

Unless you are racing or doing some serious rock crawling or adding tons of power, I wouldn't worry about welding the axle tubes to the pumpkin.........they worked stock below the springs, they'll work just as well above the springs too.

double_0_7

I'm sorry. I'm having a hard time with language today. No, I'm going leaf under axle. Not the other way around. And the 3" lift is on the leaf spring, not the shock. My plan is to put everything together, sans shock, and find an appropriate shock to put on once everything else is sorted.

The bit about leaving the existing spring perches in place is very helpful. I wouldn't have known about that.

The other thing then is that I have no idea what to do about the pinion angle. I have to do more reading. Can you (someone) explain at least the basics so I know what I'm looking for? I mean, right now, I don't even know the what to call this topic, so I can't look it up. I'm not stupid, just very inexperienced. I picked these projects specifically because I have to learn so much, and getting started is a bit daunting.

TRCM

The topic should be driveline angles or driveshaft angles or u-joint angles....(could alos replace angles with vibes)................

The diagram in your 1st post explains it pretty well, as long as you don't put on a SYE (slip yoke eliminator), as then it all changes as to how to figure it out. Basically, you want angle 1 & angle 2 to match under load, but in opposite directions. That means you will most likely have to do some trial and error to figure it out and BEFORE you weld on the new spring perches.

If you are using a 3" lift spring, it will likely come with a shim on the bottom of the spring pack to correct pinion angle that has the thick end to the rear...you will need to remove this from the bottom and put it on top of the spring, but with the thick end to the front this time.
You can remove it by taking the spring apart (a couple of c-clamps on the pack to keep it from coming apart while you remove the centerbolt will help immensely). Note the orientation of the center bolt and bolt head. It should have come with a big head on the bottom of the shim & pack, and you will need to make sure that big head is on top when you swap it, as this is what centers the spring on the spring perch and locks it there once it is all bolted together.

Yes, you can leave the factory perch on, and just weld on a new one on the bottom side of the axle tube once you determine where it needs to be. You will need to move the shock mount tho either way as it is in the way. Leaving the stock perches on may in fact help later on when you find you need to put more bumpstop on, as you may be able to bolt it to the old spring perch, but I doubt you'll need to worry about it.

Even tho you will be using a 3" lift spring and not a stock one, you will still cut your clearance under the rear of the jeep by ~ 7" by putting the axle on top of the springs, so you will have to deal with all that too.

All of this is google-able.....so you can see how it's done...bleepin jeep has a bunch of stuff like this.....you will need to buy a decent angle finder, and I recommend a magnetic one with a V on the leg to center it easily on a round item (I use something very similar to this.......https://www.harborfreight.com/catalogsearch/result/index/?dir=asc&order=EAScore%2Cf%2CEAFeatured+Weight%2Cf %2CSale+Rank%2Cf&q=angle+finder)

As long as you don't develop into an arrogant ***** who won't listen to experience, there are more than enough people on here willing to help you as well.... we all learned somewhere....and from someone.

(and even if you do, there are still some on here that will help just to be able to tell ya you were wrong.......LOL)

double_0_7

Really stupid question. If it isn't welded together yet, how do I hold all the pieces together enough to put it under load?

And thanks for the post. It was VERY helpful.

By way of explanation, I'm an electrical engineer, so I'm not stupid (or at least I don't think I am, lol), just really inexperienced at some stuff. But the way my mind works, I get road blocks that become as much a mental block as anything else. Once I get started again, I can work for a while until something else comes up that I can't wrap my head around.

double_0_7

I'm not understanding how the angle could ever NOT be the same. As long as the perches are welded in a way that holds the pumpkin flat in relationship to the ground, then centerline A and centerline C are always fixed. Centerline B can do whatever it wants, and angle 1 and agle 2 will always be the same. I'm missing something, I know...

TRCM

To do this with the spring under the axle, it will be more difficult, but not impossible....(also, ignore what I said earlier about the spring shim going on top of the spring, I forgot you are welding in new spring perches, so no shim should be needed, and you can even leave the shim on the bottom of the spring to make sure the center bolt isn't too short, but you will still need to flip the center bolt so the head that holds the spring aligned with the perch is on top of the spring)

1) Install the leaf springs by connecting them at the front eye only (snug, not tight yet), and let it hang and lay on the ground
2) Place the spring perches on the center bolt heads (there should be a hole in the surface of the perch that the bolt head will sit in to hold it there)
3) Roll the axle up, and 1 side at a time, lift the spring up until the perch is against the axle tube, then install the u-bolts & plates so they sandwich the spring & axle tube (plate will be on the bottom and the u-bolts will be upside down)
4) Snug up the u-bolts, but not super tight....you want them tight enough to not move real easily, but you want to be able to rotate the axle with them all bolted up
5) Put a jack under the hogs head and jack it all up slowly so you can connect the shackle end to the chassis (again, snug bolts here for now)
6) Once it'a all snug, cycle the suspension a few times to relieve any stress in the bushings/shackles
7) Make sure you can rotate the housing both directions - if not, loosen the u-bolts some until you can
8) Use your angle finder and get to work figuring out the angles
9) Once you go the angles figured out and set, tighten the u-bolt up good, but don't bother torquing them yet
10) Tack the new spring perches in place, then take everything apart, and weld them up good, then put it all together again and check the angles, if they are still good, then torque all bolts and yer done





To being with, it is very likely that centerline A is NOT parallel to the ground.

Yes, centerlines A & C will always be fixed if all is welded together, but they will not always be parallel to the ground or to each other.

If you look at your pumpkin right now (stock) it is not level with the ground....the pinion is slightly high/angled up, and the transmission will be slightly angled down, again, not parallel to the ground. As the leaf spring compresses, it will move the pumpkin up and back, as well as angle the pinion up slightly, all as a function of how an elliptical spring works. This causes angle 2 and centerline C to change.

For the purposes of what you want to do, the transmission (angle A) will be fixed, but the others you will have to tinker with to get the right.

Now, if you have a SYE installed, there would be no angle at the pinion, and all of it would be at the transmission.

Do some google searches on the topics, and some reading...it's not hard, but I am sure they can explain it better than I.


Here's a diagram I drew up that shows other easier ways to get the same angles. The red lines are taken from the machined surfaces of the u-joint saddles, not the saddle caps or bolts.

awg

usually with a couple of tack welds that can be easily ground away

there is a lot of info on how to do the pinion angle calculations with lifting, which will be applicable to you also, I will edit in a link later

if you dont mind me asking, what is the intent of lowering your XJ ?

double_0_7

I just want it to be a little more fun on the drive to work. I fell in love with an autocross one I saw posted on a couple forums, and wanted one. I bought this as a $1500 project not too long ago.

double_0_7

I didn't measure anything before I started taking everything apart. I didn't know there was anything to measure.

I've been doing a lot of reading, and I know what I'm supposed to be doing, but I don't know how I'm supposed to start without that stock information.

Edit: As close to parallel as possible? So I want to lower the vehicle onto the axle to put load on it, and rotate the pumpkin until angle 1 and angle 2 above are roughly the same? How do I account for rocking under acceleration or movement?

TRCM

On the stock configuration like you will have, you don't....on a SYE configuration, where there is no angle up top, you do.

You don't really need to stock info, as long as the final product angles are as equal as possible

double_0_7

thanks.

Is this how the order of parts should go?

TRCM

Yes, but your old perch will be on top of the axle tube with the u-bolts sitting on either side of it....like this