Yj leaf spring center pin size and questions

[mikeswrangler]

I was wondering what size does jeep use for there center pin bolts. I have 4" trailmaster lift springs, but im sure the diameter is the same, I can figure out the lenght I need and Im sure I could go utside in the dark cold and measure the diameter also, but its easier to just ask.

My problem is, I just bought my old YJ back and on the way home I could feel something slapping when i gave it gas from a start. I looked underneither and the u bolts were very loose. I got all new u bolts as the ones on there snapped when I tried tightening them even after heating them. With the rearend moving back and forth the lower plates had been moving around and smacking the bottom of the center pins bending them. Also with the 8.8 the top of the center pin (cylander part) isnt long enough to go through the degree shim and into the mount for the axle. The top of the center pin needs to go threw the center whole in the 8.8 mount correct as well as the bottom of the center pin goes threw ubolt plate. Or is it ok with just going threw the ubolt plate?

[ayoung]

the head on the bolt needs to sit inside the leaf spring mounting plate


honestly i cant remember what size those bolts are, i just took my broken ones with me down to the hardware store and size matched them

[Jeepfan555]

Mike I think the stock center pins at 5/16 and most after market springs upgraded to a thicker one which is 3/8.

[jps4jeep]

you also need to count the # of leafs in the pack. the center pin needs to go into the axle perch, as well as the spring plate.  Too long and you risk loosing it on a rock.

[mikeswrangler]

Yeh, I thought it had to go threw both plates. But the head of it isnt long enough to go threw a shim and into the axle housing plate. All of them I can find seem to have the same length heads (standard size) I guess Im going to have to buy shims that dont sit around the head of the center pin but undernieth it. I also went to 3 parts places including a trailer place to try and get 3 1/4" ubolts and no one sells them. They either have 3 1/8" or 3 1/2". I brought home 3 1/8" ones from work and am gonna try to make them fit. Shouldnt be an issue with an 1/8" difference. Time to head to woodward spring in brockton.

[jps4jeep]

shouldn't go through both the shim and the axle..

if it does, it should be tapered at the end to accomindate the 9* difference or what ever the degree of teh shim is.

[mikeswrangler]

Ok let me get this straight. Spring under setup. From bottom to the top. The first is the u bolt plate (which has a oval (guessing for adjustment) hole in the center of the plate for the bottom of the center pin to center into. Then I have the leaf spring. Then I have a degree shim which the top of the centerpin (cylander part) goes threw the shim and sits flush with the the shim. Then I have the axle whith a mount on the bottom of it with three holes in the mount (I thought the center pin was supposed to go into one of the holes in this also to keep it aligned?)

[jps4jeep]

I will get back to ya later, I thinks me needs to draw pictures..

[mikeswrangler]

Yeh, Im gonna get new center pins with a longer head and the ubolts I need from woodward spring tomorrow.
Id take a picture and show you but i work till its dark out .

But from what I understand from reading everywhere and my memory (which is not so good). They also need to go into the axle housing so everything stays center.

[Axle]

correct.

[jps4jeep]

Absolutly correct, just depends on the spring manufacturer..

some used a tapered center pin that extends through the shim and the axle, some use a smaller pin that goes into the shim, and then the shim has it's own extrusion that goes into the axle.