THE CHEROKEE XJ DEBUTED FOR THE 1984 MODEL YEAR AND HAD A 17-YEAR RUN WITH FEW CHANGES. THAT"S LONGEVITY! NEARLY THREE MILLION WERE PRODUCED IN TWO OR FOUR-DOOR FORMS AND IN MANY TRIM LEVELS. IN PART 1, WE"LL COVER TIRES AND ENGINES. IN PART 2 AND BEYOND, EVERYTHING ELSE.
PROS/CONS
Adaptability and parts interchangeability with many other recent model Jeeps, combined with popularity, has earned the XJ a great deal of aftermarket support. That"s the key element in any buildup. Its major limitation is a general lack of wheel well space, which tends to limit tire size. Lots of lift and fender trimming are necessary to overcome this space limitation effectively. Read on for the plusses and minuses by era.
1984-1986: The "84 to "86 models are the least expensive and least desirable XJs from the buildup POV. To make a good trail machine they need lots of upgrades. If you plan an extensive buildup and copious parts swapping, this era offers a cheap start. The ho-hum 2.5L four, and only slightly less ho-hum 2.8L GM-sourced V6, leave a lot to be desired in the go-power department. Trans choices, the base Aisin AX-4, 4-speed and AX-5, 5-speed manuals, or the TF-904 automatic, were similarly uninspiring. The transfer cases offered are now orphans, with none of the necessary buildup goodies available. Axles were the familiar reverse rotation Dana 30 up front (the disconnect version for part-time 4wd units) and the Dana 35 rear.
1987-1990: This generation is a lot more useful to builders. The legendary 4.0L six made its debut in 177hp form. Also introduced was the AW-30-40 automatic and in 1987, the NP-231 part time t-case replaced the relatively weak NP 207 and the full time NP242 replaced the NP-229. On the downside, the notorious BA-10 Peugeot 5-speed manual, a.k.a. the "Puke-a-Lot," debuted behind the sixes. The four was still offered with the AX-5 or 904 automatic. The axles were largely the same as previous years, though the rear D35 was downgraded to a c-clip unit. In "87 only, according to the Dana manuals, the trailer tow package included a Dana 44 rear axle.
1991-1996: This is the "golden age" with a very low buy-in and a very good mechanical foundation. The 190hp HO engine tops the list, as well as an improved AW-4 automatic, the great AX-15 5-speed manual made its first bow. Axles were the same as previously, though the Chrysler 8.25 rear axle was seen in small numbers. In "92 front D30s, the troublesome CAD (center axle disconnect) was eliminated and in "95, bigger 297x u-joints replaced the smaller 260x units.
1997-2001: Call it the "Classic" era. You know a SUV line is getting old when they come out with a Classic model! Still, the XJ got major interior refinements, improved electronics, exterior resculpting, some engine refinements, a NV-3550 5-speed manual replaced the AX-15, and the 29-spline 8.25 Chrysler rear axle became more commonly available. One downside is that from "00, the front axle reverted to the low-pinion, standard rotation D30, a`la the Wrangler TJ. This increases front driveshaft angularity and decreases ring gear strength by about 15 percent. There"s very little else to dislike in these late XJs, except the resale value.
TIRE FITS/HITS
This is the root buildup choice around which many other modifications revolve. You pick the tread type that fits your "wheeling style, but here"s the tire bottom line on the XJ; the magic number is 31. At that maximum tire size you can build a very street able machine using a reasonably priced 3-inch lift with minimal drivetrain mods and minimal hacking of the fenderwells. With 33-inch tires, you"re into the 6-inch lifts, more drivetrain mods and varying degrees of fenderwell trimming. You can fit 35-37 inch tires with lifts of 8 inches or above and major body modifications. Because the XJs require so much lift for the big tires, be sure to check your local lift laws and add that info to your pro/con list. The higher center of gravity makes the really tall XJ a marginal choice for daily driver, unless you are into risks. Full width axle swaps add considerably to stability, but open other cans of worms like tires that stick way outside the wheelwells and get you tickets. The chart in the sidebar nearby lists the tire fitting parameters for the XJ. An upcoming installment will fill you in on the best way to lift the Cherokee.
XJ Tire Fitting Parameters
Actual tire diameter varies according to manufacturer. Actual lift vs. advertised varies according to manufacturer. Wheel backspace listed may vary according to exact conditions. Chart biased towards XJs with at least stock 4.0L power. Fours or V6s should stop at 31-inch tires and drop one to two gear ratios lower than listed for each tire size. Axle ratio listed produced the most desirable performance, not necessarily the best MPG.
Notes: Other Mods
Items in ( ) indicated desirable upgrade above minimal.
1- Rear locker or limited slip
2- Posi-Lok for front axle
3- Alloy rear shafts D35
4- One-piece front axle shafts, 760 u-joints, locking hub conversion
5- Alloy front axle shafts, super u-joints
6- Super 35 upgrade or axle swap
7- Axle swap, D44 or Ford 8.8
8- Long arm front lift
9- Chassis reinforcement
10- Front locker or limited slip
11- Driveshaft mods & tailshaft kit
ENGINE PERFORMANCE TIPS
The engine will dictate many of your buildup options. If you run a four or even the V6, keep vehicle weight down and tire size on the small side to keep performance up. You can gear low for 44-trail performance but that will adversely affect street economy. The 4.0L, stock or modified, is adequate for nearly every use when correct gearing is used. Bottom line, there"s no replacement for displacement. Your hop-up money is not well spent on a Jeep four or a V6; the results will be minimal for the amount of investment. A swap to a larger engine (or an XJ with a larger engine) gives you more bang for your buck. Check the local emissions regs before swapping or modifying your engine.
2.5L 4-Cyl: The "93 up SMPI (Sequential Multi-Port Injection) engines are the best, but the "87-92 TBI engines are pretty good too. The carbureted engines need help. The first level for all three engines would start with a performance exhaust system from Dynomax, Gibson, or Borla, taking care not to get huge on the pipe sizes. Headers would come next, if you can find any to fit the 2.5L Cherokee. A free-flowing intake manifold should come after that. You will not find many kits listed for 2.5L XJs but 4.0L kits can be adapted. The Weber 2-bbl kit for carbureted 2.5Ls offers significant performance and drivability gains for those engines. If you want to go deeper, HESCO, Mopar Performance and Clifford Performance offer mild to wild cam upgrades that can enhance breathing significantly, but beware of losses to low rpm performance and calibration problems for the EFI. Chips are available for the "96-up EFI fours from Jet Performance.
2.8L V6: You won"t find a great many 2.8L performance goodies suitable for Jeeps. Crane, and others make some good cams for the 2.8 and Edelbrock offers several performance intakes. Weber 2-bbl conversions are available to replace the cranky feedback Rochester. Beware: It"s easy to lose the low rpm performance of this engine, so take care with cam and intake selection. The GM TBI version of this engine made 125hp and 150 lbs-ft and enterprising XJ owners have swapped these systems into XJs. The 2.8L is a power problem that shouldn"t be nibbled at. GM Performance Parts offers a 3.4L bolt-in replacement for the 2.8L that makes 160hp and 194 lbs-ft. It"s designed as a 49 states emissions replacement for S-10s. Everything swaps over from the 2.8L, but you need to use an externally balanced flex plate that matches the Jeep torque converter (three or four bolts). This is really the easiest and best way to get a major power-up for the V6 XJs.
4.0L: The 4.0L is the most popular Jeep engine of all time and you"ll get dizzy looking at all the choices available to soup it up. There are two main 4.0L versions, the 177 hp and the 190 hp High Output. The early engines used the Renault-derived Renix system, which is now just about impossible to upgrade or retune. The "91-95 used a Chrysler SBEC system, for which only piggyback chips are available, such as those from Jet Performance. In "96, Chrysler upgraded to the JTEC EFI, which can be upgraded via a programmer like Hypertech"s Power Programmer, or with a chip available from Jet and others. A variety of EFI upgrades are available, from large-bore throttle bodies, adjustable map sensors, fuel pressure regulators, oversize injectors and fully programmable EFI conversions to dial in all the enhancements.
Exhaust system choices abound, including headers and/or cat back systems from Dynomax, Borla, Gibson, Banks and many others. Free flow intakes also abound for the XJ six from K&N, Airaid and others. A built machine that sees use in water can definitely use some intake mods because the stock air inlet is low. The intake kits raise it some, but ARB"s Safari Snorkel kit is the ultimate in that department plus offers the added bonus of delivering cooler air. Larger throttle bodies are also available, but save your money unless you"ve also substantially increased the power output in other ways. A large throttle body offers little performance increase for a largely stock engine, but will let loose the horses if the engine can move a lot more air than stock.
If it"s overhaul time, or if you want a Price Club-sized ration of displacement, power and torque, the 4.0L can be stroked by installing a 4.2L crankshaft. This mod will deliver 4.5-4.7 liters depending on the amount of overbore (.060 is max). Power outputs start at about 240 and approach 300 hp, depending on other mods. Torque can range from 280 to 350 lbs-ft. Stroking the 4.0L is simple enough that it can be done by a home wrench capable of overhauling an engine, but Hesco and Golen Machine make it an easy weekend project by offering complete engines. You"ll need larger injectors and perhaps other EFI mods to make them work.
The final big ticket modification for the 4.0L is a supercharger. Currently, Hesco is the only company that lists a kit specifically for a Cherokee, but Kenne-Bell and Avenger both build kits for other 4.0L Jeeps. While each kit is different, 280- 300 flywheel hp is possible on low boost engines and torque well into the 300 lbs-ft range.
Repower: First off, a 4.0L swap into a four-cylinder or V6 rig is not easy, especially with early XJs. From "87 on it"s a bit easier if you have a complete donor rig from the same era and all the little parts. It"s cheaper in the long run to start with the "87-up 4.0L powered rig if the stock or built-up power outputs will work for you. Smallblock V8s and GM 90 degree V6s will fit under the hood of the XJ, but with no room to spare. Engine swaps in XJs are not widely supported, but Advance Adapters and Novak both offer kits for smallblock Chevy V8s and the 4.3L V6. The more fab-friendly wrenchers out there have installed just about everything practical, including Ford and Mopar smallblocks. Potentially, the Ford might be the best swap because it"s the lightest and most compact of the three smallblock V8s.
1) The first version of the 2.5L used a Carter YFA feedback carburetor. The second version used a throttle body injection system. Power outputs for the TBI varied somewhat, with the lowest being 117hp and the highest 120. The SMPI version offers the best combination of torque, drivability and power. Different power outputs are shown for various year SMPI engines, ranging from 125hp to 130 hp.
2) This GM V6 was a stopgap until the 4.0L development could be finished. The big advice for this engine is to keep it cool. It"s known for head and head gasket problems. California versions used a cranky feedback style Rochester E2SE 2-barrel Vari- Jet. The 49-states rigs used a more tractable non-feedback 2SE 2-barrel.
3) There are three basic versions of this fine engine. The early 177hp Renix unit, the "91-99 190hp "High Output" version, and the "00 and up variant. This last engine has many internal improvements and a better intake manifold, but substantially different accessory mountings. There is little bad to say about any of these engines, other than that they were known for cracking exhaust manifolds.
SOURCES:
4 Wheel Parts
www.4wheelparts.com
800-284-9840
4 Wheel Drive Hardware
www.4wd.com
800-913-8205
Advance Adapters
www.advanceadapters.com
800-350-2223
Edelbrock
www.edelbrock.com
310-781-2222
Golen Engine Service
www.golenengineservice.com
800-591-9171
GM Performance Parts
www.gmgoodwrench.com/GMPerformanceParts
Hesco
www.hescosc.com
205-251-1472
Jet Performance
www.jetchip.com
800-535-1161
K&N
www.knfilters.com
800-858-3333
Novak Conversions
www.novak-adapt.com
877-602-1500
CAPTIONS
Many people like the clean lines of the two-door Cherokee. The 31x12.50-15 BFG tires on this red beauty give it a filled out look and a performance boost without serious adverse drivability penalties on the street. They offer at least 3 inches more clearance under the axles and do not require an expensive lift. They also are about as much as a stock drivetrain can handle.
Wheelwells full-o-tire! Even 33s look huge on an XJ. Many people think that 33s mark the practical limit for an XJ, where the needs of the trail, the pocketbook and street friendliness can be reasonably balanced. You may disagree.
The 258ci AMC six, the first version of which debuted in 1964, provided the original DNA for the 2.5L (150ci) four, as it did the 4.0L six. The four predated the six by three years. There is little wrong with these engines but they just can"t supply the getup and go most people require. Shown is a carbureted engine, which cranked out a meager 103 hp.
The first generation 4.0L produced a stock 177 hp. The only downside to the "87-90 engine is the Renix EFI. Next to nothing is available off-the-shelf to upgrade it and this somewhat limits the other mods you can make. The more technically savvy have figured work-arounds for most of the problems. Some owners have adapted over the later EFI, often including a HO head.
