Jeep Wrangler YJ Overview

While the Wrangler YJ wasn't a radical transformation from its predecessor, there were many small changes that either pleased or annoyed Jeepers. The most notable change was the switch from Jeep’s famous round headlights to a square headlight design. Jeep also wanted to design a vehicle with more creature comforts, which meant sacrificing many of its off-roading capabilities. 

Many exterior features of the Wrangler YJ are still interchangeable with older Jeep CJ parts. The YJ still supported a leaf spring suspension and retained its 2-door design, although there were some major changes to the suspension, drivetrain, and other parts of the Jeep model including:

• Less ground clearance and a wider track
• Wider springs and added sway bars for improved handling
• Wider windshield with square headlights (the biggest YJ model indicator) 
• Quieter transfer case 
• Automatic transmission was introduced in 1994 for 4-cylinder models
• Throttle body fuel injection system (‘88 models and above) 
• Larger axle u-joints
• Corrosion-resistant galvanized sheet metal frame that prevented rust

The ‘87 YJ might have served as a poor test dummy for the Wrangler line, but the Jeep Wrangler did add many features throughout the YJ generation we enjoy on JK models today. New features included fog lights on the Laredo, larger U-Joints on the last YJ model year, an extended roll bar on ‘92 models, and even anti-lock brakes became standard by 1993. 

The YJ Jeep length was approximately 164-184″ L x 74″ W x 73″ H, and many CJ owners are able to swap out their rusted frame for a brand new Wrangler YJ frame. As for towing, the YJ’s frame was rated to pull 2,200 lbs. 

While the YJ generation may be the most controversial of Jeep Wrangler's history, it still represented a major improvement over its predecessor. Even the ‘87 Wrangler with its 2.5L AMC 150 I4 engine and horrid NP207 T-case had better handling, heating, and interior space than older, unreliable CJ models. Of course, the NP207 T-case was dropped the next year, and for six-cylinder owners, the 4.2 L AMC 258 with its carb setup was replaced by the 4.0L 242 with a fuel-injected CID setup. 

Even if you did own the ‘basic 87 model, Laredo, or Sport, you still had the option to swap out the standard engine for the CJ’s 4.2L six-cylinder, 2-barrel carburetor. The Wrangler also added door locks to its steel half doors by ‘88 and provided better seals for its soft rooftops.

Many people from this generation complain about the endless length of vacuum that came with early Wrangler computer systems. This was also fortunately replaced by ‘91 when it finally introduced a standard 4.0L CID engine for all its models. 

Though the Wrangler YJ generation was built for passive drivers, it still had many capabilities for off-roading. With a suspension lift, you could increase your off-roading angles and enjoy the power to get through harsh terrain with a 4.0L engine.

Toward the end of the YJ generation, we saw both six and four-cylinder engines enjoy a vastly improved NP231 T-case. Even the Wrangler winches and towing capabilities were far improved from the days of the dinky old CJ model, which was no prince itself. 

While the Wrangler YJ was far from perfect, so is the first new model of many manufacturers. With a few small improvements and some aftermarket accessories, an old Wrangler YJ could run just as well as a new JK. Of course, some problems definitely affected early Wrangler YJ models, which is why it often has a bad reputation-minus the square headlights of course. 

• With lower ground clearance, the Wrangler had limited hard-wheeling and off-roading capabilities.
• The Carter carburetor on early models ran into lots of problems, even off the assembly line. 
• The Peugeot BA 10/5 manual transmission was historically unreliable (87’-’89).
• The NP207 T-Case and hydraulic slave setup made replacing a failed Peugeot BA 10/5 transmission incredibly difficult. 

With new CAFE (Corporate Average Fuel Standards) standards, early Jeep models had to sacrifice power to meet emissions standards, which resulted in having to deal with the largest hydraulic vacuum lines you've ever seen. Fortunately, by 1989, Jeep started replacing their horrendous transmission system with a more reliable AX-15 transmission. By ‘94, Wranglers were fitted with a brand new hydraulic master/slave setup for an improved drivetrain. 

The Wrangler’s 2.5L AMC I4 engine remained the platform of choice for the four-cylinder owners, and the more-powerful six-cylinder was also available. 1991 also saw the introduction of the more powerful 180-horsepower 4.0 L engine that reigned superior over its 4.2 L 122hp predecessor. The new 4.0 engines also enjoyed a more reliable computer carburetor system over its predecessors. Owners could choose between five-speed manual or three-speed automatic transmissions.

• 4.2 L AMC 258 (1987-1991, carburetor)
• 4.0 L AMC 242 (1991-1995, fuel injection)

• 2.5 L AMC 150 (carburetor)

YJ Six-Cylinder Manual:

• Peugeot BA-10 (1987-1989)
• Aisin AX-15 (1988-1995)

YJ Six-Cylinder Auto:

• TF999 (1987-1992) Non lock up
• TF999 (1992-1995) Electronic Shift

YJ Four-Cylinder Manual:

• Aisin AX-5 (1987-1995)

YJ Four-Cylinder Automatic:

• TF904 (1994-1995)

Transfer Case:

• NP231 (various YJs from 1987 had the NP207)

Before 1991, early YJ Wranglers were plagued with an unreliable hydraulic computer-controlled carburetor system. Consumers could choose between a 2.5 L AMC 150 TBI fuel injection engine or a computer-carbureted 4.2L engine, both of which were strapped by the horrendous Peugeot BA 10/5.

A computer-controlled carburetor system is designed to handle fuel the same way as a regular carburetor, except it struggled to keep a steady air/fuel ratio when a leak occurred.

Motorists often recommend a fuel-injection system that will provide a more consistent air/fuel ratio over a carburetor. While not in use anymore, computer-controlled carburetor systems were susceptible to holes and leaks that would limit the amount of air entering the engine. This resulted in lost power and increased engine temperatures. 

• Laredo
• Sport
• Sahara
• Olympic
• S Model
• Renegade 
• Islander

Most special edition Wranglers only enjoyed different trims and higher price tags. The Islander replaced the Sporty decor and featured tropical stickers/decals, a center console, the option for a full or half door Jeep, and was available in both engines. The Islander only featured a great selection of tropical themed colors. The Islander also exemplified what it was made for: light off-roading on a beach. 

Then came the Jeep Renegade from 1990 to 1994. A remake of an old classic, the Jeep Renegade featured a fiberglass bumper, options for a hard roof and rear defroster, as well as slightly bigger 4.0L I6 engine.

The Jeep Renegade didn't offer much more capability for off-roading or towing. It mainly consisted of a standard YJ body and engine with a few modifications. It’s considered one of the most controversial vehicles of this generation. 

YJs get the short end of the stick in most cases, but that doesn’t mean it can’t be a versatile off-road rig. At ExtremeTerrain we offer aftermarket accessories that will make the old Wrangler YJ act like a modern-day Jeep Rubicon. 

• Lift kit for more ground clearance
• Roll cages to protect passengers
• Sway bar disconnects 
• Replace a Dana D35 rear axle for a Dana D44
• Replace fender wells with plastic fender flares