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Q&A How-to: Jeep YJ & TJ Wrangler Tire, Suspension, Steering & Brakes 

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TJ Rubicon with 4

TJ Long-Arm Versus Short-Arm Lifts

From: Norm F.

Sent: Saturday, December 17, 2011 1:21 PM
To:
  4WD Mechanix Magazine
Subject: Long arm kits for 2004 Rubicon

Moses,

I read with great interest you technical article on your web site concerning the installation of the Full-Traction Lift Suspension “Ultimate” 4-inch lift kit.

I have a 2004 Jeep Rubicon with a little over 36,000 miles on it. It has the 42REL automatic transmission and an after market short arm lift kit on it. The wheels are 16X8 with 265X16 tires. The dealer believed it to be a factory lift, but it does not have factory lower control arms. I am assuming the former owner installed the present lift kit. The Jeep is in great condition, but to be truthful, I am concerned with the present lift kit due to many clangs and squeaks AND steering wondering at highway speeds over 50.

I enjoy making modifications to it almost as much as using it off road. While my usage is mostly off road, I do use it for trips around the Carson City area and I plan on driving it to Moab in spring and fall to enjoy that area as well. Hence, any modifications I plan on making must be highway capable and off-road worthy.

I am interested in a 4-inch lift to allow for the present 33 inch tires. I am not really interested in going much higher than 33s, for an upgrade to 35s would eventually lead to an upgrade of the axle ratio from 4:10 on both the front and rear axles.

Having said that, I have been investigation various long arm suspension lift kits from ProComp, Full-Traction, and Rubicon Express. I would think these would provide better highway handling and off-road characteristics. Although these would be approximately a $1000 more than the Ultimate kit you installed, I would consider it worth it if the off-road and highway handling characteristics would be greatly increased with the long arm systems.

I have talked with 2 different 4WD part stores with one recommending ProComp with the other indicating they have had good luck with the Full-Traction kits. Since 4WD owns ProComp, I consider that recommendation may be biased. I have no input on the Rubicon Express system.

If you could discuss the merits of the long arm systems, and if you could make your preferences known, I would greatly appreciate an e-mail from you on this subject, or a reference to one your many technical articles.

Sincerely,

Norman F.

Reply from Moses:

Norm, in my view, the long-arm is a must for 35” and larger diameter tires. The Ultimate works well to 33” size. I have a 6-inch long-arm on the XJ Cherokee (Full-Traction built) that works fine on-highway with 33” tires. Long-arm, in itself, is not as much an issue on-highway if the kit is well-engineered.

Full-Traction Suspension is conscientious about the needs of the front end geometry, whether short- or long-arm. The long arm’s main advantage is a milder arc-of-radius (essentially, caster change) over a broad range of wheel travel. If you lift your Jeep to gain long travel for larger tires, then the long-arm kit makes better sense. I believe 33” is the biggest tire diameter for a TJ short-arm front suspension. Bigger tires than that, go long-arm. 33” tires and a long-arm system is not a liability with the Full-Traction designs…

Regards,

Moses

TJ Wrangler shock absorber

TJ to YJ Shock Swap Will Not Work

From: Tim H.

Sent: Thursday, May 12, 2011 8:54 AM
To:
 4WD Mechanix Magazine
Subject: shocks

 

Moses,

 

Do you know if the stock shocks off of a 2005 Jeep Wrangler will fit my 1989 YJ? I need shocks badly and have an opportunity to pick these up for very cheap.

On May 12, 2011, at 19:11, "4WD Q & A" qanda@4WDmechanix.com> wrote:

Tim...According to listings, no…The shock mounts and lengths are different…

 

Moses

 

Mild YJ Wrangler Lift Issues

 

-----Original Message-----

From: Keith B.

Sent: Wednesday, April 13, 2011 11:33 AM

To: 4WD Mechanix Magazine

Subject: Quick Question

 

 

I know I've asked before, but now that tires cost more than lift springs I think I may have to finally purchase a YJ lift.

 

In the 1.5 " category who is best

 

Superide?

 

Black Diamond?

 

Rough Country?

 

Thanks for your reply.

 

Keith B.

 

Black Diamond came from Warn Industries and has remained a decent brand.  In the 1.5" to 2" lift category, you do want a leaf spring package and not a shackle lift. As you know, a shackle lift will alter caster angle and rear pinion angle as well.  (You can remedy some of this with wedge shims and longer center bolt heads if you're determined to lift via shackles.)  A quality lift kit should have Canadian/U.S. steel, and this is a question worth asking.  The correct lift springs will have an arch that accounts for pinion and caster angles; some lift kits integrate the springs, new/heavy-duty shackles, all urethane bushings plus shock absorbers in the package.

 

On a YJ, consider a track bar relocation bracket essential if the track bar is retained...The panhard rod at the rear axle is often eliminated with a YJ lift kit, take note of the manufacturer's instructions...Gas charged shocks actually work quite well at keeping wheels on the ground. OE has been gas-charged for years...

 

Trust this helps...You know the questions to address when selecting a lift kit. I would go for 2" minimum lift via suspension if you plan 31"x10.5"x15" tires or equivalent on 8" rims with 3.75" backspacing. Sounds like you're planning for tires that size.  The backspacing should provide enough track width increase to offset C.G. issues created by the lift.

 

Moses

 

YJ Wrangler Lift: Which Way Do the Rear Axle Shims Fit?

From: Clay B.
Sent: Friday, March 04, 2011 4:11 AM
To:
  4WD Mechanix Magazine
Subject: Rubicon Express 2.5" Lift Shims

Hi, Moses,

I'm replacing the stock suspension with the RE 5015 2.5" lift kit. the kit comes with 2 degree shims for the rear axle. I've been researching to determine the positioning of the shims. Does the wide portion face the front or rear of the jeep? It would seem this best for the driveshaft angle, but when researching, I can find nothing definitive on the RE website, and have not found anything that states this for the YJ. While your web site has the TJ lift kit, it certainly is different for the YJ.

Thanks/Clay

YJ Wrangler Rear Leaf Springs with Lift

Response from Moses:

Hi, Clay! The leaf spring shims adjust the rear axle pinion angle and driveshaft U-joint angles. The objective is to achieve proper U-joint angles on the rear driveline. Assuming you still use the stock, single-Cardan joints at each end of the rear driveshaft, you want these two U-joint angles to cancel each other—essentially, the joints should be at the same angle from opposite reference points. Using a protractor or U-joint angle gauge, measure the U-joint angles with the YJ on flat ground and curb weighted.

If you have installed a slip yoke eliminator and use a CV-type joint (double-Cardan joint with self-cancelling angles) at the front of the rear driveline, you’ll want to angle the rear axle pinion to 1.5 to 2-degrees (slight tilt). Again, measure this angle with the Wrangler on flat ground and normally weighted. This slight tilt allows enough angularity to rotate the bearings in the U-joint caps.

As far as your shims are concerned, use them in whichever direction achieves the proper driveline and U-joint angle. There are no clear directions because people use various driveline types and some even drop the transfer case slightly. The guiding principal is to get your U-joint angles correct. If wrong, you will have driveline vibration and risk of U-joint failure.

A final note: Make sure the rear driveline coupler safely engages the transfer case. If a slip-yoke, you want enough engagement to assure safety when the suspension drops fully and the rear axle articulates. The shaft slip coupler should be as close to the stock position as practical with your lift kit installed and the Jeep on flat ground, weighted.

Regards,

Moses

TJ Wrangler: Lifted and Leaning Rightward

 

Moses, I just had my TJ Wrangler lifted as you shared in the magazine’s premier issue. After driving for a short period, I noticed that the Rubicon is setting down approx 0.5”‐1” inch on the passenger right front side when measured from the ground to the bumper and ground to the fender. She is exactly the same when measured from the ground to the axle, and there is no difference in measurement when checking the suspension from different locations. While I hate to think of torque twist or anything like that, it is only ½‐inch or so, and the installation shop was pretty blunt: they cannot figure it out. They assure me the suspension is rock solid dead on, and the vehicle does ride and drive fantastic!

 

The lean may have been there before, and I didn't or could not see it because of the closer frame to axles spacing with the OEM suspension. Maybe that is the way she was from the factory? The shop checked out the ‘crookedness,’ and they think the problem lies in the sway bar links and mounts on the axle. They switched the coil springs side to side and thought the vehicle was level with the sway bar still disconnected. Hooking it up again, the truck leans to one side. They think the best solution is to use a different style sway bar disconnect that’s adjustable to get the lengths perfect on each side and level the truck correctly.

What has caused the sway bar to line up or mount with a lean to one side? I do not see the correlation. Thanks for your response, Moses, I need some insight here…Joe M.

 

Joe, this is interesting…If the vehicle sets level without the sway bar connected and not when the bar is attached, the front axle may be offset in one direction or the other. Full‐Traction Suspension systems have a provision for adjusting the front track bar to center and align the axle. This track “arm” in engineering terms is supposed to rise and drop on a radius that will keep the axle aligned as it moves up and down. The shape of the track bar, its mounting points and the alignment of the axle are critical to your issue. To begin, make sure the lift kit’s track bar drop‐bracket is in the proper position at the left side of the frame. Check the sway bar’s lower disconnect link locations at the front axle. These FTS kits use weld-on relocation brackets; the attachment points for the brackets must match positions shown in the instructions.

 

If I were addressing your problem, the first thing to check would be the axle’s lateral position with the vehicle at its normal, weighted curb height. If the track bar has been adjusted with the axle at full drop, which some shops do in error, the track bar may force the axle toward the right side when vehicle weight is on the ground and the springs compress. With the sway bar connected, the sway bar and disconnects will try to center the axle. In doing so, there would be bind that could cause the right side spring to load and compress.

 

The clue here would be a cocking or binding of the disconnect links. The sway bar is a torsion bar, essentially, and this creates force. In a static, curb height mode, there should be no bind or loading on either disconnect link. Here, the tip‐off would be links that are very difficult to disconnect or a sway bar that either rises or sets when one link is disconnected. My bet is that the sway bar is binding when the TJ is at static height. The fix would be to adjust the track bar with the axles loaded.

 

Like my discussion of Joel Z.’s driveline issue, the proper alignment of the axles should be done with the axles bearing weight. When I install a lift kit on TJ or XJ models, I start by setting the axles in their centered positions on tripod stands with full vehicle weight on the springs. I note the frame/body and axle lateral (side-to-side) alignment before removing any suspension parts or the springs. With new springs in place, I compress the suspension under vehicle weight, then set up the track bar length in this mode to assure that the axle is both in alignment laterally and unbound— at the vehicle’s static, weighted curb height.

 

I align the axles on tripod stands, lowering the frame to place full vehicle weight on the stands. This determines the static height, loaded position for the axle. The axle is precisely aligned laterally, and I then raise the frame straight upward to unload all spring tension before removing the coil springs. With the axle housing in lateral, side-to-side alignment with the frame/chassis, I remove the track bar, steering linkage and sway bar (top) before loosening suspension link arms. With new suspension and springs installed safely (bottom), the new dropped track bar is adjusted with the axle laterally aligned and the vehicle’s weight bearing on the axles (at static, loaded height).

 

After installation of any kit, I do a four‐wheel alignment check. On the stands, a diamond check is useful for a ballpark test. With heavy string, check the right front axle to left rear axle distance, using a clear reference point like the center of a front knuckle joint to a common position on the rear axle backing plate or dust shield flange. With this measurement taken, you can do the same thing from left front axle to right rear axle. If these lengths are equal, the axles should be reasonably parallel and in track alignment. By choosing identical front axle, rear axle and side to side reference points, you can increase this test’s accuracy.

 

FTS long‐arm lifts include a new disconnect link relocation bracket. This modification requires welding the brackets at a precise location on each side of the front axle. Follow instructions closely. I have MIG welded the new bracket in place. Painted and finished, it looks “factory.” This is the only welding modification necessary.

 

At this point, the vehicle should go on a four‐wheel alignment rack. (See my article on alignment, using affordable FasTrax 91025 alignment equipment. Click here for details!) Full-Traction’s long-arm kits have provision for adjusting caster, pinion angle, axle parallel, axle square-to-frame centerline plus the lateral axle positions. Given this much adjustment, there is plenty of room for correction—or error. I have installed these kits with the vehicle on a side arm hoist and tripod stands. During the installation, I keep the axles in the same lateral position as when I detach them from the chassis. Again, I adjust the track bar length with the vehicle’s weight on the axles. In the process, I’ve had great success with axle alignment…On one TJ, I installed an FTS Ultimate kit that resulted in nothing more than a 1/3-turn adjustment of one out of the six adjustable suspension arms to bring the entire chassis into square and track— the four-wheel alignment was verified on a $40,000 beam alignment machine!

 

The main objective is that the four wheels remain square (axles parallel) and track properly with each other (lateral position of each axle is correct). A four-wheel alignment rack is the final test. My guess is that your TJ’s axles are not in lateral alignment. The front axle is bound and loading the right side springs. If that were not the case, the sag issue would be due to coil spring lengths.

 

You say that the springs were switched left to right, and that should have adjusted for any length issue. Frame straightness could be an issue, but that would be a very remote prospect. Responding to the long shot troubles, torque twist would be to the left side of the vehicle in terms of drop. So rule that out. Then there’s the possibility of an aggressive tie-down when the Jeep was on the transport trailer or that the vehicle may be within spec for acceptable factory frame error. On the four‐wheel alignment rack, axle bowing will show up when checking front axle camber angles. I’ve discovered that side-to-side camber seldom matches due to factory beam axle welding methods and tolerances; the right and left side camber angles should be within factory specification, however.

 

The overall concern is that the axles are square with each other and track in the correct path fore-and-aft. If the issue were as simple as spring height, torque twist might actually level your vehicle over time. (Your TJ’s low side is now the passenger side.) I’d be looking for track bar offset and bind or an out-of-square installation. Verify square with the string method in diamond-cross. The chassis should be at curb height when you perform these checks.

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