Moses Ludel’s 4WD Mechanix Magazine – Jeep XJ & MJ Tire, Suspension, Steering and Brake System
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Buy a Cherokee and Lift It!
From: Chad A.
Sent: Monday, February 27, 2012 10:43 PM
To: Moses Ludel
Subject: RE: XJ Cherokee
It has been a while but, I think that I have finally found a XJ. It is a stock 98 Cherokee Sport.The body is in good condition and it runs well.
If I can work out the deal, I think I will pick it up tomorrow.My first question is, I want to lift the Jeep so I can fit 31s without rubbing.
Can you recommend a good lift? I see so many options and I want to make the right choice the first time.As with my CJ7, I want to keep a low center of gravity.The Jeep will be daily driven with some trail riding and exploring with the family.
I want the Jeep to be family fun and I think the XJ will be a great fit for us. I want to be able to enjoy the outdoors safely with the whole family. The nice thing about a XJ, is it can get me to school and work during the week, and hit the trails on the weekends.
Thank you for all of your help.
Chad, 1998 is a good model year. Our ’99 now has 139K and runs strongly…Lifts are tricky with the XJ Cherokee. 31″ puts your Jeep in the mild lift range, which often works okay with stock drivelines. Sometimes, however, the rear shaft will be problematic, with a vibration challenge. The fix is the SYE kit from Advance Adapters and a CV-type rear driveline. You tilt the rear axle pinion upward to 1.5 to 2 degrees U-joint angle, the CV at the front of the rear driveline will self-cancel.
I did the six-inch long arm kit from Full-Traction Suspension, more costly and definitely requiring the SYE and CV rear driveline. (You can find my coverage of these changes at the magazine site.) I’m pleased with the overall package, and my wife drives the XJ regularly. This is the way to go for 33″ tires but requires ring-and-pinion gearing changes to 4.10 or even 4.56:1.
31″ tires might be small enough diameter for the OEM axle gearing, you can correct the speedometer with a driven gear (plastic) tooth count change. Consider the SYE to eliminate vibration risk.
Trust this helps…Keep up the good work, Chad!
XJ Cherokee’s New Lift and a Vibration, Too!
From: alex c.
Sent: Wednesday, March 09, 2011 6:00 PM
To: 4WD Mechanix Magazine
Subject: Jeep XJ
I’m not sure if you remember me, but about a year ago you were coming out of Starbucks and I was jogging down the street when I saw your Jeep XJ in the parking lot and took a look at it. We started talking about Jeeps, my time in the Marines, just shooting the bull, and about my own 2000 XJ. Well, I’ve just recently lifted it (went with the Rubicon Express 3.5 inch super flex with full leaf packs on 31×10.5 BFG All-Terrains) and am experiencing a front end vibration. More often, the vibration is from the rear driveshaft, but I’m almost positive that this is from the front driveshaft. I was wondering if you have any suggestions on what this might be (I haven’t had the time with school and work, or a decent day to crawl under it and take a look myself). I appreciate the advice…I’ve been doing all my own work to my XJ, and it’s a fun, learning adventure. Hope to hear back from you.
From: 4WD Q & A
Sent: Thursday, March 10, 2011 6:19 AM
To: ‘alex c’
Subject: Lift and vibrations
I do remember our talk about XJs…The Jeep looks very cool, Alex…The height and tire size are sensible, and the front vibration, if accompanied by a steering shimmy, is commonly labeled the “death wobble”. This is generally too little front axle caster angle created by the installation of the lift kit. When you lift, you need to restore/adjust the caster angle. I did a thorough article on alignment, available at the website with this link:
If the Cherokee has too little caster angle, common with lifts, the front driveline angle at the pinion shaft is incorrect as well. This can cause front driveline vibration. Check and set the caster. When caster is in range, the front U-joint angle will be, too…This may cure two issues at one time. Also, make sure the front driveshaft’s splined coupler rides within its original range of travel. Axle position (with relationship to the frame/body) can change with a lift kit; this alters driveshaft coupler engagement, which can cause vibration.
Lastly, I’m assuming you did not slide the front coupler apart if you detached the front driveline. If you did, the alignment of the front U-joint must be in phase/alignment with the joints at the rear of the front driveline. Out of phase, the driveline will vibrate. If you shift the coupler on its splines, and even maintain phase (180-degree shift), you can alter the balance of the shaft and cause vibration. Note that these shafts are assembled before balancing.
Keep me posted!
Lift Kits: XJ Cherokee versus MJ Comanche Rear Springs
Sent: Friday, January 21, 2011 7:07 PM
To: 4WD Mechanix Magazine
Subject: xj/mj help
i have a 94 xj country with a 5 1/2″ lift . im about to buy an 87 short bed comanche. can i physically take the rear springs off of the xj and bolt them on to the mj? are the mj spring connecting points on the frame farther apart than the xjs? i cant find any info anywhere. from what ive read, from the front doors forward, the xj and mj are identical, meaning i can literally take the entire front suspension off of the xj and bolt it on to the mj without any issues-correct? are the rear shackles the same design as the xj as well? from what ive read , i would not have to lengthen the drive shaft for any lift under 6″ -is this true ? the lift in the rear of my xj is 2″ spring, 2″ shackle, 1 1/2″ lift block and the front is 4″ spring and 1 3/4″ spacer , and info and help you can provide me is GREATLY appreciated- thank you
Reply from Moses Ludel:
Lance, this is an excellent question, since there are so many XJ and MJ interchange components. I researched OEM Jeep spring numbers and aftermarket lift kit springs. The MJ Comanche and XJ Cherokee rear springs are distinctly not the same. As you suggest, there is great parts interchangeability from the cab forward and the powertrain, even the rear axle. However, the MJ Comanche has a significantly longer wheelbase and longer rear leaf springs. The 6-foot bed models are 113.1-inch wheelbase; the 7-foot bed models have a 119.4-inch wheelbase. All XJ Cherokee models have a 101.4-inch wheelbase with shorter rear leaf springs.
There are even differences in the spring plates for the Comanche’s 6′ versus 7′ bed models. Frame brackets differ between the two bed length models as well. As a footnote, the standard MJ springs are 4-leaf. There were 5-leaf heavy duty springs available in 1990-91 heavy duty models with the prized Dana 44 rear axle.
Aftermarket (lift type) springs are different between the MJ and XJ. Although I could not find specific eye-to-eye spring lengths, the overall length of the MJ rear leaf springs are considerably longer than the XJ Cherokee rear leaf springs. The spring eye to plate center-bolt measurements also differ. MJ Comanche models were built to carry a hefty bed load over a set of long leaf springs.
The later, heavy duty “Big Ton” package (known as the “Metric Ton” package outside the U.S.) for long-bed models includes heavier-duty leaf springs and wheels, larger tires and an upgrade to a Dana 44 rear axle in place of the Dana 35. This increases stock payload capacity from 1,400 pounds (640 kg) to 2,205 pounds (1,000 kg). The Metric Ton Comanche’s payload rating is higher than many full-size pickups of its era. Much of this capacity is rear spring length and rating. Trust this helps, Lance!