1 + 1 <> 2

My wife has a 2001 Cherokee that just rolled over 134k. The suspension needed freshed up, the rear in particular was sagging, and as this is her DD I wanted to keep things mild but add just a little lift as we are going to get a travel trailer next spring and I thought beefing up the suspension slightly would be advantageous. I also planned on running 30x9.5x15 winter tires and getting some 255/70's for summer, figured they would look good with the slight lift and help fill out the wheel wells. Here's the run down: for the front I got a set of OME springs (930's I think) and a new rubber isolator. The specs on the springs indicated they would ride 1 3/4" taller than stock. I figured I'd leave the original isolator installed and sandwich the new one between it and the spring. I estimated 2" lift by doing that. On the rear I purchased a set of the Crown heavy duty springs which are said to be the up country springs that are 1" taller than stock. Also, I purchased a JSK shackle which also stated would add 1" lift over stock. There's my 2" in the rear. Well, I just got everthing installed yesterday and much to my surprise, 1 + 1 does not equal 2! The front ended up 3" higher than stock and the rear is 4" higher! I'm using 17 1/2" in the front and 17" in the rear from the center of the wheel to the bottom lip of the fender flares for my measurement.

So, I'm open to ideas as to how to proceed. I assume the springs will settle some, but not 1-2". I'm actually okay with the front, but you can see a slight rake, not too bad, but somewhat noticeable. Wondering if I should just order a set of the medium duty springs and replace the heavy duty ones? Or go with a stock shackle? Or . . . ? I'm also confronted with needing to shim the rear to get the driveshaft angle back where it needs to be. I'm not interested in lowering the transfer case. I got on Quadratecs chat last night and they recommended a 4 degree shim. Does this sound right? Perhaps the lesson here is, buy a kit instead of trying to piece something together, but this seemed pretty straight forward based on my research.

Help, before my wife see's her Jeep that I was not suppose to get crazy with.

david

Did you wait till the rig was on the ground before tightening all the suspension hardware?

^ X2 on that.

FYI, most lift springs do run a bit above what they're supposed to, because they know people will be unhappy if they don't get the specified lift... with a heavy front bumper/winch and armor on the back. My OME HD 2" springs in the back gave me 3.5" of lift.

As for the shims - get yourself a cheap angle finder from Lowes/Home Depot and measure the angle of the transfer case output shaft (you can take it easy on yourself and just measure the valve cover of the engine, they are at precisely the same angle unless your drivetrain is about to break in half) and the angle of the rear axle pinion. The rear axle pinion should be pointed down a bit below the angle of the transfer case output shaft / valve cover - a degree or two is fine. If that doesn't solve the vibration issues I assume you are now having, you will need to do a slip yoke eliminator install, which will require shimming the rear axle so that the pinion is a few degrees below the angle of the driveshaft instead.

RCP Phx said:

Did you wait till the rig was on the ground before tightening all the suspension hardware?

Click to expand...

X2, also , you may be surprised about the springs settling. the leaves will settle. it may take a couple of weeks. my 3.5" RE packs netted nearly 6" of lift, but have settled to about 3.25".
If all else fails, remove the JKS shackle and replace with the OEM one.

Thanks for the quick reply, guys. Yep, she was on the ground when everything got tightened up.

Kastein, I'm not sure I follow where you say: "The rear axle pinion should be pointed down a bit below the angle of the transfer case output shaft / valve cover - a degree or two is fine. If that doesn't solve the vibration issues . . . "

Are you saying that if the rear axle pinion isn't pointed down that it needs shimmed? Or is there some way to adjust the pinion angle without a shim?

nope, you need shims... or to cut the mounts off the axle housing and weld them back on at the new "right" angle :roflmao:

It shouldn't literally be pointed down, it should be pointed "down" as in 1-2 degrees below parallel with the valve cover/transfer case output shaft.

Gotcha, thanks for the clarification. That's what I was thinking but wanted to check.

Most new springs take a while to wear in. My front RE 3.5 spring are 3 years old, with a bumper up front and they still sit at 4.25 inches.

ok just wondering did you measure befor and after to get those measurments? if so your befor measurement wasnt a stock measurement due to the sagging. assuming your suspension was an inch or more sagged you probly actually got only 2-3 inches from the rear springs. same concept for the front also. a measurement befor isnt actually stock ride height its below stock height due to the sag

The 17.5" front and 17" rear is what I had found (probably from a search here) as the stock ride height. Before the swap I had 17" in the front and the rear was 16". I now have 20.5" front and 21" rear. So I'm calculating my "gain" in height (over stock) by subtracting the stock ride heigth from what I have now.

I used a 2" coil spacer up front and UpCountry leaf springs that I purchased from a Jeep dealer. The rear leafs gave me about 2" of lift, but after a year they had settled a bit. I added a .75" shackle and all is good. Mine measures from the center of the wheel to the bottom of the flair 19.5" in front and 19" in the rear. It's also a 2001.

floyd said:

The 17.5" front and 17" rear is what I had found (probably from a search here) as the stock ride height. Before the swap I had 17" in the front and the rear was 16". I now have 20.5" front and 21" rear. So I'm calculating my "gain" in height (over stock) by subtracting the stock ride heigth from what I have now.

Click to expand...

ok good just wanted to make sure. http://www.naxja.org/forum/showthread.php?t=912893 has measurements to get your lift height

Now, without a SYE you would want your tcase output to be parallel with the pinion. Having them parallel eliminates vibrations. You'll need the shims with the SYE. Having taller shackles, rotates the pinion towards the t-case, which may cause vibration because you desturb the factory geometry. A t-case drop works because it drops the rear of the t-case enough to bring the output back parallel with the pinion.