I am doing this write up to help inform JK owners what to look out for and how to set start the process of setting up their JK's during and after a lift. This write up is not intended to be a "How to" as lifting a JK is the same as lifting a TJ in most regards other than steering, and I have not upgraded any steering components as of yet. I will also begin a build thread of my jeep and update it with more info specific to my Jeep.
The victim: 2010 JK Rubicon Unlimited with 54,000 miles.
The first thing we decided to do was take some before measurements.
Front Uptravel = 3.5 (bumpstop pad to bumpstop cup)
Rear Uptravel =5 (bumpstop pad to bumpstop cup)
Clearance to frame = 13.625
Clearance to gas tank skid = 10.5
Front hub center to fender flare lip = 20.5
Rear hub center to fender flare lip = 21.25
To get an idea just how good Jeep engineers are, we wanted to cycle the axles and get a baseline for a completely stock setup.
- Loosened all control arm bolts. Basically take the torque off them, so the sleeve inside the bushing can rotate with the arm. Otherwise the bushing would twist and bind as the axle is moved around bad for long term durability.
- Lifted the Jeep up as high as possible and supported from the axle tube. Put jack stands under the axle and removed the tires. Also put jack stands under the frame, just behind the lower control arm mount.
- Unhook the lower shock mount and allow the shock to hang. Loosen the front track bar bolts , both frame and axle end (do not remove). Remove the sway bar links.
- Lift the Jeep up from the axle until the weight is off the jack stands. Remove the stands from under the axle tube, and lift the stands under the frame as high as possible. Drop the Jeep down on the frame, and allow the axle to drop to full droop.
- Use channel locks to pull the jounce bumper out of the cup on each side. Have a buddy stand or bounce each side while you remove the spring.
- Be mindful of ABS lines, brake lines, breathers, wiring harnesses for diffs, etc. These will be nearly fully extended, if youre not careful you might break something.
We positioned two floor jacks (with wood cribbing on top) under the axle in order to push the axle to full bump. We checked these with a totally stock suspension setup; stock tires and 35s (315/70/17).
The first thing that we noticed was the stock front track bar flag caused interference at the frame. This flag must be positioned horizontally inside the bracket. If yours is sticking out of the top of the bracket like this, then you need to change it so it clears.
You can see the track bar has a severe bend to clear the stock diff cover. You can also see the drag-link, tie-rod, track bar and control arms tuck nicely. The upper control arms actually tuck into the engine compartment in front of the engine. Notice the frame side front track bar mount will tuck well below the tie-rod, and even below the axle tube. Notice the track bar also has a bend to clear the pitman arm.
In the rear, you can see the axle tucks nicely as well, and the track bar has a bend to clear the diff. Notice the frame side rear track bar bracket will pass by the bumpstop pad - beware of this for bolt clearance. Notice the exhaust has a specifically placed dent to clear the track bar on the driver's side.
FULL FLEX & TIRE CLEARANCE: We installed a tire on each axle, and used the floor jacks to push the axle to full flex on the side where the track bar mounts to the frame, in order to check fender clearances. As expected, no clearance issues are observed with stock tires.
Looking good up front.
However, upon installing the new 35 (315/70 R 17) tires, we find major clearance issues do arise.
We find the front needs 2.5 bumpstop extension to prevent major tire vs fender flare damage. Also note the tire rubs the front bumper extension, therefore we did not check lock-to-lock tire clearances in order to check/adjust steering stops.
After taking the Jeep for a shakedown run the rubbing on the front bumper extensions was the largest problem with this lift. For this reason I am recommending anyone with 35's and 2.5-3 inch lift to get a mid width or stubby bumper. Personally I am going to go with the endcaps that go over the stock bumper. Below is a picture of the rubbing that occurred on the trail.
We find the rear needs 3 bumpstop extension to prevent major tire vs fender flare damage.
Bottom line: the stock flares & bumper ends need to go, so bumpstop extension can be reduced to regain uptravel.
BRAKE LINE LENGTH
At full droop the track bar pulls the axle to the driver's side, extending the driver's side brake line tight. We find the front brake lines to be too short, and used a length of string to measure for new lines. We find the new lines need to be about 27.5 from end to end (approx 3 longer than stock).
During full droop check, we find the front brake lines to be too short to allow the axle to rear full droop with the new shock length. It was necessary to loosen the brake lines from the frame, and allow them to hang loosely so we could complete all the necessary testing. Using a length of string to measure for new lines, we find the new lines need to be about 25 from end to end (approx 3 longer than stock).
We also find breather hoses, locker wiring, and e-brake line length will could be adjusted slightly to accommodate the increased travel.
AFTERMARKET TRACK BARS
Before reaching full bump, we find the front track bar has major clearance issues with stock length control arms. We measure 2.5 bumpstop extension requirement to prevent the track bar from hitting the diff. This is a disappointment since this is not mentioned on their website, and this track bar is advertised to fit 1+ of lift. Clearly this is not the case, and you would need 2.5 of lift just to maintain stock uptravel with this track bar. Due to these issues, the stock track bar was reused after the lift install. We may sleeve the track bar to extend its length, but the axle was only off center about ½ after completion.
Front track bar vs diff cover issues are well known in the TJ series, with a multi-year, 100+ page thread still active today.
We find the rear track bar clears nicely from stock height full bump to full droop with the lift. This was a pleasant surprise based on the issues seen in front, and the issues previously seen in the TJ series. The rear track bar was not a limiting factor of uptravel or downtravel, when using the stock mounting points. A raised bracket has high likelyhood of pushing the bar into the exhaust or other components, and would require adding bumpstop extension. Also, if you using adjustable control arm arms, lengthening the arms to push the axle back in the wheelwell may also lead to issues with the bumpstop pad, exhaust clearance, track bar clearances, etc.
We measured the stock shock length to be:
Front = 14 compressed, 22.75 extended (8.75 travel)
Rear = 14.75 compressed, 23 extended (8.25 travel)
At full bump, we measured the distance between the front shock mounts to be 15
The new Bilstein shock lengths are:
Front (PN:24-146708) = 15 compressed, 24.65 extended (9.65 travel)
Rear (PN:24-146715) = 15.4 compressed, 26.4 extended (11 travel)
This indicates the new front shocks could potentially fit with no bumpstop extension and the rear shocks need 0.75 bumpstop extension.