Help with 4 link problem

fbronc69 · Aug 8, 2021

Hello everyone. I bought a YJ that had been stretched with coil overs at each corner. I am trying to work all the bugs out and have a problem with the suspension unloading when I have it in 4wd, hold the brake and put it in drive. The front will lift about 10 inches. It will also suck down in reverse. The anti squat and dive are both above 100. I have new coil overs on front and rebuilt ones on the rear.

I am looking for any ideas that you might have to help this problem

The front arms: lower arms are 13deg, upper 4deg
The rear arms: lower arms are 8deg, upper 0deg.

Thanks for your help.
Ty

TBItoy · Aug 8, 2021

have you actually driven it/wheeled it?

Kinda sounds like the front and rear gear ratios aren't the same.

fbronc69 · Aug 8, 2021

TBItoy said:
have you actually driven it/wheeled it?

Kinda sounds like the front and rear gear ratios aren't the same.

The ratios seem to be the same. I just drove in 2wd and 4wd. The front lifted in rear low with front neutral. I have driven it around on dirt roads but have not wheeled it yet

Beerj · Aug 8, 2021

Sounds like your anti-squat might be pretty high. Need to move your instant center out. Basically try to get your upper and lowers closer to parallel. Do you have any adjustment in your brackets?

TBItoy · Aug 8, 2021

fbronc69 said:
The ratios seem to be the same. I just drove in 2wd and 4wd. The front lifted in rear low with front neutral. I have driven it around on dirt roads but have not wheeled it yet

Oh, in your original post you said it was in 4wd.

In 2wd Low (rear low) and holding the brakes, I guarantee the front brakes are holding and the rears are not (gear reduction is letting it drive through the brakes) and its essentially trying to drive over the front suspension. You said the front links were all at an angle so it makes sense that it would lift. If you could at least get your upper link flat and drop your lower links to where they are flatter, it will help and be better overall. But it's always going to jack the frontend when you're holding the brakes.

If you've never driven a rig with coilovers or airshocks, they act a lot different than regular coils or leafs, in that they have spring rate throughout the entire shock travel (ie they are always trying to extend). Most vehicles with leafs or standard coils only have a few inches till the springs go neutral from ride height.

Unless you plan on driving around in 2wd low, I wouldn't worry about it, and see how it acts in 4wd.

fbronc69 · Aug 8, 2021

This is what I have for angles

fbronc69 · Aug 8, 2021

TBItoy said:
Oh, in your original post you said it was in 4wd.

In 2wd Low (rear low) and holding the brakes, I guarantee the front brakes are holding and the rears are not (gear reduction is letting it drive through the brakes) and its essentially trying to drive over the front suspension. You said the front links were all at an angle so it makes sense that it would lift. If you could at least get your upper link flat and drop your lower links to where they are flatter, it will help and be better overall. But it's always going to jack the frontend when you're holding the brakes.

If you've never driven a rig with coilovers or airshocks, they act a lot different than regular coils or leafs, in that they have spring rate throughout the entire shock travel (ie they are always trying to extend). Most vehicles with leafs or standard coils only have a few inches till the springs go neutral from ride height.

Unless you plan on driving around in 2wd low, I wouldn't worry about it, and see how it acts in 4wd.

Thank you for the great info. This my first coil over rig and maybe it is ok if not normal.

TBItoy · Aug 8, 2021

post some pics of the rig

Bebop · Aug 9, 2021

How tall is the rig ?
Belly distance to ground at ride height ?

87TPIYJ · Aug 11, 2021

Have you tried running the 4 link calc? Yea everything is dependent on your CoG, which I highly doubt is dead center of the wheelbase. Most people use the top of the bell housing bolt as a swag on jeeps. Definitely sounds and looks by the little diagram you made like you AS is too high.