Jeep Wrangler YJ 1987-1995: Performance Modifications

By Don Alexander and Quinn Thomas

Jeepers rejoice! Bring new life to your classic Jeep YJ with this new guide to off-road performance.

More than 685,000 YJs were built from 1986 to 1995. They featured heavier wider leaf springs, track bars, and sway bars for improved handling. A massive range of parts are offered for these vehicles, which include lift kits, wheels up to 37 inches, larger brake rotors, high-performance aluminum remote reservoir shocks, stronger driveshafts and U-joints, and Dana 60 conversions.

In Jeep Wrangler YJ 1987-1995: Advance Performance Modifications, veteran author Don Alexander covers the 4.0 engine, transmissions (automatic and manual), transfer cases, axles, differentials, and driveshafts, steering boxes, brake upgrades, shocks, springs and lift kits, chassis strengthening, and interior upgrades.

Whether you want to do some simple upgrades, such as a lift and tire combination, or want to go all out with a rock crawler-style suspension and an engine swap, this book will guide you through the process.

• Language: English
• Publisher: Car Tech
• Release date: Nov 15, 2019
• ISBN: 9781613255742

Book preview

CHAPTER 1

JEEP WRANGLER YJ

The first Jeep to use the name Wrangler was the YJ in 1986 for the 1987 model year. The most distinguishing features of the YJ were the rectangular headlights and the bend midway up the grille. Today, many YJs have been upgraded to become first-class trail rigs.

In 1986, American Motors Corporation (AMC) launched the first Jeep Wrangler: the 1987 YJ. The Wrangler YJ replaced the CJ7 and was in production through the 1995 model year. While the history of the YJ provides interesting reading, looking at how the YJ fits into the current Jeep world is the first order of business.

According to some Jeep engineering types, the Wrangler YJ possesses the strongest, most rigid of all the Jeep chassis. That rigidity provides a significant advantage for off-road activities such as rock crawling. The stiff frame allows the suspension to do its job more effectively by flexing less. Of course, adding a well-designed roll cage will greatly increase the torsional rigidity of the chassis, and that creates the potential for a very serious rock crawler.

The original YJ looked similar to its predecessor: the CJ7. Refinements to the YJ allowed it to appeal to a broader audience with greatly improved creature comforts and on-highway drivability.

Since we are avid fans of rock crawling, we built a YJ in stages from simple to extreme. After all, world-class rock crawling trails are in our backyard with the John Bull, Dishpan Springs, and Gold Mountain trails minutes away. Johnson Valley OHV area is home of the Hammers trails and the iconic King of the Hammers desert and rock crawling race and is a mere 45 minute jaunt from us.

The Jeep Wrangler YJ is a very popular platform for building extreme rock crawlers.

The Jeep Wrangler YJ was one of the first vehicles equipped with true off-road capable tires, in this case the 30x9.5R15LT OWL Wrangler AT Tires. The standard YJ came with a soft top and half doors. (Jeep is a registered trademark of FCA US LLC)

The first stage for our YJ project will accommodate 33-inch tires. This will take a 4-inch lift. Next, we’ll use a spring-over conversion that mounts the springs over the axle but retains the stock springs. Bigger tires, up to 35 inches, can be used with this setup. Finally, an extreme rock crawler that is still California street-legal looms on the horizon. Coilover suspension, a stretched wheelbase, tires up to 40 inches, and an engine swap should allow us to rip up the rocks on trails such as Sledgehammer, Chocolate Thunder, Backdoor, and Jackhammer and then drive home in the street-legal beast when we’re exhausted.

Where aftermarket parts number in the thousands for the Wrangler JK, the YJ is not so blessed. But many parts are available and most will be showcased. The rocks are calling and we are ready to take them on!

Jeep Wrangler YJ History

Of all the Jeeps prior to the JK in 2007, the YJ stands out and is the most recognizable model. The most notable difference from the CJ7 visually is the grille and the rectangular headlights. When the YJ hit the showrooms in 1987, it was much criticized by the Jeep purists. Of course, the same thing has happened with the introduction of every new Jeep Wrangler model. The negative sentiment fades quickly as newcomers join the ranks of Jeep owners and the old timers soften because the new model actually offers many improvements. That happened with the YJ; except for the square headlights, many aficionados still malign the YJ because of the headlights.

The new Wrangler YJ was designed to improve comfort and highway handling to attract a broader daily driver market. The YJ went on sale on May 13, 1986, and production ceased at the end of 1995 with the 1995 production year. YJs were sold into the middle of 1996. Total YJ production topped 685,000 units.

In the last couple of years, the Wrangler YJ popularity has skyrocketed. And the resale prices are reflecting this trend. Prices have nearly doubled in a short time span. The popularity of the Wrangler JK offers the most likely explanation for this. In the last model year of the Wrangler JK, a Rubicon is more than $45,000 and the new JL Rubicon will top $50,000. High-mileage stock 2007 JK Sahara and X models fetch $10,000 and more. Modified, high-mileage JKs start in the $15,000 price range. Wrangler TJ Rubicon models with some modifications start at $10,000 and up. Similar YJs with some modifications start around $5,000. Because Jeepin’ has grown so fast in popularity, consumers have looked at other Jeep Wranglers as a starting point. The YJ offers many bargains even as the prices climb.

The Wrangler YJ, while similar in appearance to the CJ, was a totally new design. The YJ used leaf spring suspension, though the springs are wider. The YJ also featured track bars and sway bars for improved on-road handling. Overall, the Wrangler YJ is larger than the CJ7 and shares several components with the Cherokee XJ.

The Wrangler YJ used a 2.5-liter AMC inline 4-cylinder engine or the optional 4.2-liter inline 6-cylinder AMC 258 until 1990. In 1991, a fuel-injected 180-hp 4.0L inline-6 (the AMC 242) replaced the 112-hp 4.2L 6-cylinder engine. The NP207 transfer case was used in 1987 but was replaced by the NP231 the following year. This was a significant improvement for function and durability.

Shortly after the launch of the YJ, AMC was sold to Chrysler and the Jeep line became part of the Jeep/Eagle Division. This had little effect on production, as it continued at the Ontario, Canada, plant until it closed in 1992. Production was then moved to Toledo, Ohio, in the original plant were the Willys World War II vehicles were made.

The Standard S model of the Wrangler YJ was available with full doors and roll-up windows with the standard soft top. (Jeep is a registered trademark of FCA US LLC)

The Sahara option package included features such as body-color fender flares, steel wheels, interior door panels with pockets, front bumper–mounted fog lamps, and plastic ends on the front bumper. An AM/FM stereo with cassette player, rear speaker sound bar, unique cloth-and-vinyl high-back bucket seats, rear removable bench seat, and air-conditioning were all standard.

Suspension and Axles

The YJ uses Dana axles at both ends. The front axle is the semi-floating Dana 30 with a shaft disconnect system. It also has Hotchkis leaf springs, a stabilizer bar, and a track bar.

An interesting side note: the shaft disconnect system has made a comeback with the new Wrangler JL. The YJ used the disconnect system to eliminate the need for locking hubs, which are no longer needed with U-joint and CV joint axles. The new JL uses a similar system to reduce parasitic drag within the transfer case. This improves fuel economy by up to 1 mile per gallon and also reduces transfer case wear.

The Wrangler YJ uses leaf springs front and rear. The front axle assembly is a Dana 30. Most of the components are the original parts that are nearly 30 years old. (Jeep is a registered trademark of FCA US LLC)

The rear axle assembly on the YJ is a Dana 35. The original shocks were replaced by Rancho gas shocks some time ago. Only the wheels and tires are new on this Wrangler.

The front suspension on the YJ features a track bar and a sway bar. The sway bar disconnect was added to this YJ.

The 1987 Jeep Wrangler

Wheelbase: 93.4 inches

Overall length (with P225 spare): 153 inches

Overall width: 66 inches

Overall height (soft top): 72 inches

Curb weight (with 4.2L): 3,028 pounds

Transmission: 5-speed (standard)

Transfer case: 2-speed NP207

Engine (Standard):

2.5L inline-4 OHV

Displacement: 150 ci

Bore x stroke: 3.875 x 3.188 inches

Compression ratio: 8.6:1

Horsepower: 117 hp at 5,250 rpm

Torque: 138 ft-lbs at 3,500 rpm

Induction: 1-barrel carburetor

Engine (Optional):

4.2L inline-6 OHV

Displacement: 258 ci

Bore x stroke: 3.75 x 3.90 inches

Compression ratio: 8.6:1

Horsepower: 112 hp at 3,000 rpm

Torque: 210 ft-lbs at 2,000 rpm

Induction: 2-barrel carburetor ■

The rear axle assembly featured the earlier Dana 35 without C-clips. In 1989, the Dana 35c assembly replaced the earlier version. A track bar and leaf springs located the rear axle. Cherokee XJ axles, recirculating-ball steering, and other components allowed a wider track. A lower ride height and sway bars improved the on-road handling and performance of the YJ.

A spring-over axle lift was fabricated by the owner of this YJ. The tie-rod and drag link were also upgraded. The sway bar uses a quick-disconnect link to improve axle articulation. This lift along with aftermarket fenders allows the fitment of 35-inch BFGoodrich mud-terrain tires.

To make a trail-capable YJ takes a few parts and some hard work. This YJ was modified by the owner with some aftermarket parts, such as a spring-over axle lift with extended spring shackles. Good shocks and beefier steering links allowed the use of 35-inch mud-terrain tires.

The Dana 35 rear axle assembly has worked well on this YJ since new. The owner uses it for moderate trails. The stock rear driveshaft uses a slip yoke with an old style U-joint.

The rear driveshaft used on the stock YJ is very short. While there is no issue with the stock ride height, when the suspension is lifted, the pinion angle of the rear axle becomes very important.

An optional engine for the YJ is the 4.2L inline-6 overhead valve version producing 112 hp.

The axle ratios were 4.11:1 for the 4-cylinder engine with manual transmissions, while the 6-cylinder had 3.07:1 ratios with the manual and 3.55:1 on the automatic-equipped vehicles. The 4-cylinder coupled to the automatic used 3.73:1 axle ratios. When the 4.0L inline 6-cylinder became available, it featured 3.07:1 axle ratios. A Trac-Lok rear differential was optional for the YJ except on the S model.

Many YJ options available in later years of production were the same as those available later on the Wrangler TJ. A soft top with half doors featuring soft plastic zipper windows came standard. Side windows could be removed from the doors. Full-frame doors with glass windows were an option on soft-top models. YJs ordered with hardtops came with a rear wiper and defroster. Hardtops included full-framed doors.

Half-door YJs used large mirrors with adjustable arms. Full-size doors received smaller adjustable mirrors with fixed arms. Depending on year and interior color, the YJ hardtops were available in black, white, tan, and gray.

Trim Levels

Wrangler YJs were available in the following standard trim levels:

•  The base model was also referred to as S and SE at different times during production. During the early years of production, the back seat and rear bumperettes were optional. The 6-cylinder engine was an option during some model years, but during other models years only the 4-cylinder was available in the base model. An AM radio (later AM/FM stereo) with two speakers was standard. High-back vinyl bucket seats and a heater were standard. An AM/FM stereo, cassette player, and air-conditioning were optional. In 1986, a basic Wrangler cost $8,995.

•  The Laredo package featured a chrome grille, bumpers, and trim; hardtop and hard full doors; tinted windows; faux leather interior; body-color fender flares; and alloy wheels. An AM/FM stereo with cassette player, rear speaker sound bar, air-conditioning, rear removable bench seat, and high-back cloth bucket seats all came standard. Laredo decals adorned the hood on both sides or on the lower front fenders as part of the side stripes.

•  From 1988 to 1993, the YJ was offered with an options package called the Islander. Several colors were offered, including Bright Red, Pacific Blue, Sunset Yellow, Teal, and White. Both engines were offered. Features of the package included body-color wheel flares and side steps, sunset graphics on the lower body and the hood, an Islander logo on the front fenders and the spare tire cover, Wrangler decals, optional 20-gallon fuel tank, a gray interior with high-back seats, optional five-spoke alloy wheels, floor carpeting, a center console with cup holders, and full or half doors.

•  The Sport model featured Sport graphics and, beginning in 1991, a 4.0L 242-ci inline 6-cylinder engine. An AM/FM stereo with two speakers and a rear removable bench seat came standard. A cassette player, a rear speaker sound bar, cloth high-back bucket seats, and air-conditioning were optional.

•  The Sahara option group featured most available options as standard equipment, including body-color fender flares and steel wheels. Also included with the Sahara edition are special green trail-cloth seats with storage pockets, interior door panels with pockets, front bumper–mounted fog lamps, and plastic ends on the front bumper. An AM/FM stereo with cassette player, rear speaker sound bar, unique cloth-and-vinyl high-back bucket seats, rear removable bench seat, exterior color steel wheels, and air-conditioning were all standard on this model.

•  From October 1990 until 1994, the Wrangler YJ offered the Renegade Decor Group. All Renegades came in white, black, or red exterior colors. Blue and bronze were added for the 1992 and 1993 model years. The Renegade option package cost $4,266 beyond the base Wrangler for 1991 and included special alloy wheels, fender flares, and additional features. The Renegade Decor Package included a 4.0L 242-ci I-6 engine, 30x9.5R15LT OWL Wrangler all-terrain tires, exclusive five-hole aluminum wheels that were 8 inches wide, a full-size spare tire, high-back seats, off-road gas shock absorbers, power steering, fog lamps (integrated into the front fenders), a leather-wrapped steering wheel, Renegade striping, floor carpeting, front floor mats, extra-capacity fuel tank (20 US gallons), color-keyed fender flares with integrated side steps, front and rear plastic bumpers, a center console with cup holders, courtesy and engine compartment lights, interval wipers, and a glove box lock.

Other YJ options include a hardtop costing $923 and required a rear window defroster at $164. Soft-top models came standard with half doors, but full-framed doors with glass windows were an option. All 6-cylinder Wranglers offered air-conditioning as an option. Renegades had the tilt steering wheel ($130) and an AM/FM/cassette stereo radio ($264). A column-shifted automatic was also available.

•  The Rio Grande edition was offered in Champagne Gold, Moss Green, White, Aqua Pearl metallic, and Bright Mango with a Pueblo-themed interior trim package. This trim was only available in 1995 and was added to spice up the base 4-cylinder Wrangler S models. A cassette player, rear speaker sound bar, and cloth high-back bucket seats came standard. Air-conditioning and alloy wheels were all available on this model. Red-and-orange Rio Grande decals adorned both rear fenders.

•  Many options available for the YJ in later years of production were the same as those available later on the Wrangler TJ. A soft top with half doors featuring soft plastic zipper windows came standard. Side windows could be removed from the doors. Full-frame doors with glass windows were an option on soft-top models. YJs ordered with hardtops came with a rear wiper and defroster. Hardtops included full-framed doors. Half-door YJs used large mirrors with adjustable arms. Full-size doors received smaller adjustable mirrors with fixed arms. Depending on year and interior color, the YJ hardtops were available with top colors in black, white, tan, and gray.

•  The Wrangler YJ specifications are close to its CJ7 predecessor. The YJ exceeds the length and height of the CJ7 but is actually slightly narrower. The Wrangler TJ that followed the YJ is very similar in dimensions to the YJ. The frame and some body panels are nearly identical. Engine choices for the TJ mirror those offered in the later model years of the YJ. Many driveline components share the same heritage from the YJ to the TJ.

Today, the Wrangler YJ enjoys a surge in popularity and the resale prices reflect this. Currently, Wrangler YJs in stock, good condition sell for up to $15,000. Modified YJs can fetch up to $20,000 or more, depending on condition and the extent of modifications.

Today, YJs with a few modifications make great hard-core trail rigs. Only the headlights, the grille, and the leaf spring shackles differentiate this YJ from the later Wrangler TJ.

Aftermarket product availability for the YJ is significant. In part, this stems from the similarities with the Wrangler TJ. For example, bumpers for the YJ also fit the TJ. More than 20 companies offer nearly 100 different front bumpers. Engine and driveline components also share fitment with the TJ. The product category with limited availability for the YJ is suspension and lifts. The YJ was the last traditional Jeep model using leaf springs. While many leaf spring lift options lure the consumer, few coil spring options or coilover systems are available. A dozen companies offer YJ lifts ranging from 2 inches to 8 inches. Many of the kits use brackets to move the leaf springs to the top of the axles. Only one or two coilover kits are offered. Many product options ranging from tops to body armor allow the YJ owner great latitude in upgrades and modifications. In 1987 when the YJ hit the market, 29-inch-diameter tires were considered large. By the time the top-of-the-line YJ Renegade reached the market, it featured