The Jeep JK is one of the most commonly used platforms for aftermarket lift installation and off-road use. There are many ways to lift your JK. Like most modifications, altering factory components will change the may your Jeep operates. This article focuses on knowing what these changes are and how to eliminate negative results.By Weston Chadwick – November 30, 2015
Contributors: Mount JEEP, pbujku13, Sierra JK, woodyvw9, MD5, Waiting, 4fit
This article applies to the Jeep Wrangler (2007-present).
The JK uses a complex combination of arms, braces, and rods to make a reliable and effective steering and suspension platform both on the road and off. This makes it an easy vehicle to build upon for off-road use. A lot of questions may come up when you decide to add a lift, such as, “What problems might I face when lifting my JK?” or “What type is best for my goals?” After determining the answers to your questions, you will know how to combat common problems associated with lifts for a reliable, trouble-free Jeep JK.
Adjustable Upper and Lower Control Arms
Adjustable upper and lower control arms allow you to adjust castor. The factory control arms are non-adjustable. After installing a lift (generally over 3″) the front caster angles may become more negative, creating a “flighty” feeling. This is countered by increasing the castor in the positive direction to increase vehicle stability.
Figure 1. An adjustable control arm.
When you install a suspension lift on your JK in excess of three inches, a lot of the suspension geometry changes. One of these is the horizontal position of the axle. An adjustable trackbar is needed because the factory trackbar is too short to keep the axle centered. Instead, it moves the axle to the side to keep the distance between the axle and track bar equal.
Figure 2. A front adjustable track bar.
Rear Track Bar Mount
Instead of installing an adjustable track bar for the rear, some companies provide a new track bar mount. This relocates the rear track bar to maintain factory position of the rear axle.
Figure 3. An aftermarket rear track bar mount.
Once your JK exceeds four inches of suspension lift, you may need a modified driveshaft to maintain factory-like universal joint angles. Although a modified driveshaft is usually not required or included with a suspension lift installation kit, damage to the factory driveshaft and differentials can occur once the universal joints reach their maximum working angle.
Figure 4. An aftermarket driveshaft.
Once your lift exceeds 2.5 inches to 3 inches, you may need exhaust spacers. These move the exhaust crossover pipe further back, creating more clearance between the exhaust and front drive shaft/crossmember.
Figure 5. An installed exhaust spacer.
What are some different types of lifts?
There are many ways to lift your JK depending on the height desired and the components you’d like to change. These range from body lifts and leveling kits to coil spring lifts and coil spring spacers.
What size lift do I need to fit 35″ tires, 37″ tires, etc.?
You do not need a lift to fit 33″ tires that are less than 10″ wide when using stock wheels. If you have aftermarket wheels, the backspacing must be 4.5″ to clear a 33″ tire. 35″ tires will require a 2″ to 3″ lift while 37″-40″ tires will require a 4″ lift. Aftermarket fender flares will help increase the fender-to-tire clearance.
What are some companies with lift kits for the JK?
Teraflex, RK, and Metalcloak are some commonly used lift kit companies.
What size tire can I fit on the stock tire carrier?
A 35″ tire can fit the dimensions, but the weight may damage the tailgate and carrier. Owners install reinforced hinges and extended tailgate bumpstops to counter the problem.
Will my JK’s handling suffer with a lift kit?
This comes down to several factors such as alignment, type of tires, and type of lift. If you decide not to purchase adjustable track bars and control arms, then your alignment may be off and not correctable after the lift. This will affect your JK’s handling. Larger 35″+ tires will create more rolling resistance, increasing the steering effort required to make a turn, although with power steering this is not a large concern. Some lift types simply modify the stock components rather than replace them with modified versions. This can create wear and make the components work outside of the designed operating range, reducing their effectiveness on road.
How will larger tires affect my JK’s drivability?
Larger tires will make your engine rotate faster to cover the same amount of distance in any gear. Those with final drives lower than 3:73 and tires larger than 35″ will notice the increased engine revolutions at highway speeds.
How will a lift effect the Electronic Stability Program?
Your lift kit may alter the way the E.S.P. functions. You may be required to shut the program off or re-calibrate it to restore proper operation.