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How To Build It - The Jeep Grand Cherokee

Posted in Features on March 19, 2014 Comment (0)
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How To Build It - The Jeep Grand Cherokee

The Grand Cherokee has had several generations since its initial introduction in 1993. The ZJ ran from ’93-’98, WJ, the last Grand with front and rear solid axles, from ’99-’04, WK , the last Grand with a solid rear axle, from ’05-’10, and WKII from ’11-present. These iterations of the Grand Cherokee are all pretty different, with the first two (the ZJ and WJ) sharing the most parts, and enjoying largest aftermarket following. We are gonna focus mainly on the first two generations of the Grand Cherokee since the latter years are still fairly pricy on the used market and lack the enthusiast following of the ZJ and WJ.

The ZJ was really the first mass-produced Jeep designed and built by Chrysler, initially intended to replace the XJ, but eventually basically replaced the last Jeep with a V-8, the ’92 fullsize Grand Wagoneer. Powered by the 4.0L with an auto transmission (and the very rare ’93 ZJ with the AX15), early on the ZJ also got the Chrysler 5.2L Magnum V-8 as an option. Despite this, both the V-8 with Quadra-Trac standard and 4.0L-powered ZJs with Quadra-Trac as an option (NP249) held a viscous coupler that would not lock even in low range. This means you could get stuck with one tire spinning even in low range. This means Jeeps with Select-Trac (NP242) would be slightly more desirable with its truly locking center differential. Also, if you want to go off-road, avoid the 2wd versions of the ZJ or WJ.

The ZJ was the first mass-produced civilian Jeep with coil and link suspension on all four corners. The front suspension is very similar to that of the XJ, with the rear suspension approaching the setup later found in the TJ Wrangler. In the last year of the ZJ a 5.9L Limited ZJ is probably the most desirable, with the introduction of a powerful 5.9L Magnum V-8. The downside with the 5.9L Limited Grand is associated with the fact that it’s one year only. Lots of the parts on the 5.9L Limited are specific to that vehicle making them hard to find and expensive when available. After the ZJ the WJ debuted as a slightly larger Grand with an optional new 4.7L dual-overhead cam V-8 or the venerable 4.0L I-6. WJs also featured a revised four-link front suspension with a track bar and a three-link rear suspension with an upper wishbone. The WJ was also the first Jeep to wear the 5-on-5 bolt pattern, on wider axles, featuring bigger brakes, and factory steering with a raised passenger side knuckle for a nearly flat drag link. The best part of these Jeeps is that today they are cheap. The bad? They are generally pretty used up, and with all the electronic luxo-gizimos that many Grands have, reviving them is a chore. Still there is plenty of fun left to be had with either a ZJ or WJ. Look for one that spent its former life as a well-maintained family truckster.

Mud
Since there is a V-8 available, go for it. Churning up the muck with a 4.0L will work, but nothing beats a V-8 in the wet stuff. Adding suspension lift to your Grand will help gain more clearance for tires, but like with other coil sprung Jeeps much over 4 inches will throw suspension angles out of whack enough to make a long-arm conversion appealing.

When new a ZJ or WJ with all its viscous couplers and limited slips fully functional were pretty potent at getting traction off-road (as long as the tires worked). Now that all these wearable items have seen 150,000, maybe 200,000 miles expect them to be worn out and in need of a rebuild before reliable traction can be achieved. Having said that, you could have lots of fun in the slick stuff with a V-8-powered Grand with fully functioning limited slips, a T-case viscous coupler, and some decent mud tires. A snorkel will help your Grand’s mill breathe more easily in the deep stuff, but don’t forget to pay attention to the venting of your transmission. As a rule Jeep autos don’t tolerate the introduction of water too well, and the Grand’s autos are no exception. As most Grand Cherokees are sent out from the factory as fairly luxurious vehicles, most are gonna feature more electronic gee gaws than would be advisable for use in the mud. If you could find a low-optioned Grand with a V-8 for mud, that would be advisable over one with every electronic option available.

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Rock
When building a Grand for rocks either the V-8 or 4.0L make a good starting point. If you are gonna run a 4.0L you are better off with an earlier ZJ with the AW4 or swapping to one as the 42RE is lighter-duty and is known to develop problems with heavy use. The AW4 is a heavier duty transmission that stands up to rock use fairly well. As for axles, if you have the Dana 44A we say lock it and run it until catastrophic failure takes it out, or as we would advise any Dana 35 owner, prepare to swap it out as soon as cash allows. We know of several people and companies that have swapped JK Rubicon axles under WJs. Both are of similar width and the brackets can be made to work. Likewise, swapping a ZJ to TJ Rubicon axles would also be a good option for anyone wanting to play in the rocks up to about 37-inch tires. Anything larger than that and you are gonna need some custom axles. Add in some aftermarket beef to the knuckles and axlehousings, and Rubicon axles should be good up to 35- or maybe 37-inch tires in a WJ or ZJ. If you plan on keeping the Dana 30 in the front of your ZJ or WJ we would suggest dropping the CV axleshafts at your earliest convenience for chromoly aftermarket units or the rare factory U-jointed parts. We’d also advise dropping a worn out NP249 or NP247 for the more tunable and rebulidable NP231 built for the power of a V-8, or go to an aftermarket gear driven T-case like an Atlas II (you know you want one!).

The second generation of Grand Cherokee is the WJ sold as ’99-’04 models. These Grands are a little bit larger and offer a stronger Unitbody construction than the ZJs that they replaced. Power comes from either the venerable 4.0L or a 4.7L SOHC V-8 that was even available with a five-speed auto. The 4.7L was also available as a high-output version making 265hp and 330 lb-ft of torque. The second generation of Grand Cherokee is the WJ sold as ’99-’04 models. These Grands are a little bit larger and offer a stronger Unitbody construction than the ZJs that they replaced. Power comes from either the venerable 4.0L or a 4.7L SOHC V-8 that was even available with a five-speed auto. The 4.7L was also available as a high-output version making 265hp and 330 lb-ft of torque.

In general some stout bumpers, rocker guards, a rollcage and good fender trimming are all gonna be your friends if you want to put your Grand in the rocks. Chassis stiffeners with a few being available in the aftermarket for ZJ at least, are again a good idea for long term off-road use. As for the WJ, stiffeners are supposedly not necessary, as the Unitbody is stiffer than either the ZJ or XJ. Again, we suggest the lowest lift height possible and fender trimming to get to the tire size you want to play on in the rocks. Our WJ runs 33s and about 4.5 inches of lift thanks to a long-arm suspension system from Clayton Off Road. The Suspension works well on-road, on twisty crawling trails, and does decently at speed in smaller bumps off-road. We have friends running a ZJ with Notch Custom’s flares running 4 inches of lift and 35s, so keeping a Grand low with big tires is possible.

Sand
Any Grand with a V-8 is gonna do best in the sand, and a few have been prepped for Jeep Speed or other “go fast in the dirt” racing, so the know-how is out there. The front Dana 30 is gonna be alright for use in the dunes, but you are gonna want to add some strength to prevent bending as well as limit straps to keep the suspension from falling apart in the air. Look into aftermarket housing brackets or tube inserts to strengthen the axle housing as the front axles are known to bend in both the ZJ and WJ. As for the rear axle you will want to either upgrade to another axle or if nothing else add strength with an axle truss of sorts to prevent bending. For the WJ, full size truck axles at about 65 inches WMS to WMS will make for a nice fit, but you’ll lose the ABS (for good or bad) unless you use more modern axles with wheel sensors. We know of one WJ owner getting speed signal information from their swapped in T-cases (as the NP247 in the WJ lacks a speed sensor) rather than wheel sensors. To adjust signal, just splice in a Superlift True Speed between the replacement T-case and CPU speed sensor wire. Any of the transmissions (with the exception of the 42RE) will be alright in the dunes, but we would definitely add an aftermarket inline transmission cooler to keep the heat out of any of the autos in a Grand.

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