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The Trooper is one of the most underrated sport-utility vehicles around. Often ridiculed or dismissed as an oddity by owners of Jeeps, Land Rovers, and owners of the Big Three, the Trooper never gained the popularity it deserved and thus many people do not realize how capable this little truck is. Production of all ISUZU consumer vehicles ceased in the North American market in 2004. ISUZU Trooper production ceased in 2002.
The Trooper features an independent front suspension design. However, unlike many IFS systems of the era, the design Isuzu utilized is quite strong and will hold up well to abuse. The front differential is one of two different models: the Isuzu Corporate 8-bolt, or the Isuzu Corporate 10-bolt. The 8-bolt was used in Troopers until mid-87, where the entire front suspension was changed and the 10-bolt was incorporated into the design. The 10-bolt front axle was used in Troopers from mid-87 until the final Trooper rolled off of the production line. All Troopers featured front disc brakes.
The rear axles are slightly more varied than the front. The Isuzu Corporate 10-bolt rear axle was used in combination with the 8-bolt front axle in the pre-88 model year trucks. It's not nearly as strong as the 12-bolt and also features drum brakes. In mid-87, the Trooper received a major upgrade to the rear end in the form of the 12-bolt axle. The 12-bolt introduced disc brakes to the rear of the Trooper, providing a boost in stopping power and torque handling in preparation for the 2.6L 4ZE1. Slight modifications were made to the axle design in 1991 (for accomodating the new 4-link coil-spring suspension and wider track of the '92 model year). In 1995 roughly 2 inches was added to the width of the rear axle for the wide-track Trooper (along with longer front axle shafts), although all other features such as spring perches and link mounts remained unchanged. All 12-bolt axles from 1992 through 1997 featured a 4.56 gear ratio. For the 1998 model year, significant changes were made to the axle, including thicker axle shafts and different spline count, resulting in the Modified 12-bolt axle (with 4.30 gears). Most internal parts of the Modified 12-bolt are not interchangable with the regular 12-bolt axle. Note that the bolt count is the bolts in the ring gear not the pumpkin to the housing.
The Trooper has always had a rather high rear axle ratio. 4.56 (41/9) ring and pinion gear sets were used in the 1984 model Troopers all the way up until around 1998, when 4.30 (43/10) gear sets were used due to the availability of much torquier 3.5 liter V6 engines. The only exceptions to this were the 1987 turbo diesel trooper (it was available for one year only and only 200~ of them came to the USA) 4.11 gears were used from the 4x4 81-87 pup to slow the engine RPM at highway speeds so a 86 T\D trooper can be upgraded to 4.11 by taking the gears from a 4x4 isuzu pup; and the 1989 RS Trooper, which used a 4.77 gear ratio. 4.77 gears were reportedly also available in some 4-door first-generation models with the "Big Tire" option package.
The bolt pattern for Troopers is 6x5.5 with a 108mm (4.26") center bore. Many Toyota and Nissan stock wheels will fit, but most GM wheels have center bores that are too small (78mm center bores). Some mid-80's GM trucks and K5 Blazers do have factory wheels with a larger center bore that fit however. Note that the Canyon/Colorado have 6x5.5 bolt patterns with 100mm bores, and Trailblazers/Envoys have 6x5 bolt patterns.
Lugnut sizes is 12x1.5mm with with 60* conical end for factory Isuzu wheels. If using Toyota wheels most Toyota wheels have a stepped shoulder and are hub-centric, that's why they use lugs with straight shank and washers. The Toyota wheels have a large enough hole to fit over the Isuzu hub, but will not center because the diameters are off. Isuzu factory mags are lug-centric and the wheel centers about the lug holes only and not the center hub.
First Generation 1984-1991
1984 - Isuzu introduces Trooper into U.S. 1.9l engine. 4 speed MSG transmission. Automatic locking hubs. 10 gallon gas tank (identified by the gas filler mid ship in front of the rear axle). Round sealed beam headlights. Antennae on drivers side windshield pillar. Two doors. Rear seat has horizontal sliding windows. 15x6 rims with 225/75/15P tires
1985 - Won the 4x4 of the year from Petersons 4wheel drive magazine. last year for the 1.9L in all 4wd models, end of the 4wd 4sp MSG trans and mid ship gas tank. 1985 was the last year for any Isuzu to have a 4sp in a 4wd model. the 4wd MSG 4sp was sold 1979 to 1985 and was the "only" 4wd trans available in those years.
1986 - Isuzu Introduces Trooper II into U.S. (This was the same as a Trooper, but with no rear seat at the time of import, so it was imported at a lower tariff rate as a truck. Rear seat installed by dealer). 2.3l carbureted engine, or a 2.2L turbo diesel bolth had a 5 speed MSG-5 transmission only made for 86-87 troopers and pup 4x4s. 10-bolt (Isuzu Corporate) rear differential. 8-bolt (Isuzu Corporate) front differential. Tachometer added to gauge cluster. New gauge cluster added between center vents with oil pressure, temperature and gas gauge. 4 door model offered. Two door model has same body as previous years. Rear spoiler (used to keep continuous air flow across rear doors to help prevent exhaust gases from entering) and roof rack offered as options. Air conditioning a non-Isuzu dealer option. 21.5 gallon fuel tank located behind the rear axle. Alloy wheels on LS model.
1987 - Transition begins. Square headlights like later models. Same driveline as 86. Some report 12-bolt rear end and 10-bolt front end differential, though officially the 10/12 combination was not released until the 1988 model year. also last year for 2.2L T\D engine. first year for LT235/75/15 tires.
1988 - 2.6L 4ZE1 (121hp / 146 lb-ft) fuel injected engine introduced. MUA-5 5 speed manual transmission standard with Aisin-Warner A340H 4 speed automatic as an option on the 2.6L. 12-bolt Isuzu rear differential introduced. The 10-bolt rear diff used in rear of '84-'87 Troopers moved to the front in the improved IFS. Antenna located on front passenger's fender. Rear step bumper on LS and higher models with tow package. A "Special Edition" Trooper featuring special badging and a split rear seat that converts to a bed was available this model year only. (Note: the split rear seat that reclines all the way down to the cargo area behind the seat was available in later years as well).
1989 - Short wheelbase RS version with 4ZE1 2.6L is produced and available in the US only in this year. On long wheelbase models, the GM 2.8L V6 (LL2) is introduced as an option as well as the 4 speed GM 4L30E automatic transmission, available on the 2.8L V6 only as the 4ZE1 2.6L was paired with the A340H - an Aisin transmission. All 4L30E and MUA-5 manuals had gear driven transfer cases, while the A340H had a chain driven transfer case.
LS, S, XS, and limited versions available. 2-door available in S and XS. LS and S commonly available. XS and 2-door models available in select areas.
According to Jerry Lemond, the '84-88 2 door was the long wheelbase version, the same length as the 4 door as only one chassis was used in those years. The distance from the rear edge of the door to the front of the rear wheel well opening is roughly 22.25 inches on the long wheelbase 2 door model. All 2 doors in '89-91 were short wheelbase, as all 1st gen regular length (long wheelbase) Troopers after '88 had 4 doors.
S model is base with a metal lined interior and only available with 15x6 steel wheels, although 15x7 aluminum wheels with 31x10.5x15 tires were an option on all trim levels, but apparently with the 2.6L only. All 15x6 rims received 235x75x15 tires, and auto-locking hubs were standard with the manual transmission. Interestingly, according to the '89 sales brochure the rear wind deflector was only available on the S trim.
The LS is a higher end model with chrome trim, cruise control, lower dash cover to hide wires underneath the steering column and glove box, power windows and power door locks (note - not all LS had PW and PDL as it was an option), chrome front bumper, privacy glass (the semi-reflective light tint),retractable cargo cover, reclining front captains chair with adjustable armrests, reclining split back rear seat, velour upholstery, rear step bumper, built-in trailer hitch and aluminum 15x6 wheels.
The XS is positioned between the S and the LS, they did not have power windows or power door locks and had different trim, and was available only with the 2.6L like the RS. Interestingly also, the folding rear seat option (not to be confused with the reclining split back rear seat) was only available on the S and XS.
Curb weight is listed as 3600/3680 manual/auto for the 4 door, but actual weight of a 1990 2.8L manual was 4056 at the scale Here are two posts to http://www.planetisuzoo.com/ that explains the model year differences in the first-gen Troopers:
Jerry Lemond posted an explanation of the 1986 and 1987 differences as follows: The major (running gear) difference is in the frame in the front. The 1987 has the '86 front axle assembly, which is the 8-bolt (same as all '86's), but it has the '88 front suspension, upper and lower control arms, different ball joints, and a somewhat removable front under-engine cross member like all late Troopers. It also has a removable transmission cross member, basically the same (10-bolt) rear axle, except for being about four inches wider, and the '87 has the '88 and later front brakes with the '86 rear drums.
A former Isuzu technician offered a general overview of the First-Gen Trooper differences: 1984-1985 had a 1.9 liter carbureted OHC 4-cylinder engine and a 4 speed MSG transmission with a two-speed transfer case, and an 8-bolt front and a 10-bolt rear differential. Automatic-locking hubs completed the power flow to the front wheels.
The 1986 had a 2.3 liter carbureted OHC 4-cylinder and a 5 speed MSG transmission with a two-speed transfer case, still with the 8-bolt front and 10-bolt rear through 10/86. This was also the first year of the 4-door. A 2.2 liter 4-cylinder OHV turbodiesel engine was available for '86 and has proven to be very popular in today's used vehicle market.
The 1987 was a transitional year, with the chassis and suspension of the upcoming 1988 model, but the running gear of the '86. The '87 model (11/86-06/87) had the larger front a-arms, knuckles, and hubs as on the '88, but with an 8-bolt front with one-year only longer CV axles, and a 10-bolt rear with drum brakes. This, too, was a one-year only, slightly wider rear axle than the '86 to match the wider front track of the revised suspension. It still had the 2.3 carbureted engine and 5-speed MSG manual. There seems to have been a small number of diesels produced for '87 and are difficult to find today.
The 1988 (beginning 07/87) was the culmination of improvements started in '87. It had the carry-over stronger front suspension, but now had a 10-bolt front diff. A new 12-bolt with disc brakes held up the rear. It had the new 2.6 port-fuel-injected 4-cylinder OHC engine with a stronger, MUA 5-speed and two-speed transfer case. An automatic trans was an option for the first time. It was a 4-speed overdrive Aisin-Warner in the same family as found in the Toyota and Jeep Cherokee. This AW30-80-LE model had an integral hydraulically-controlled chain-driven two-speed transfer case. Manual-locking hubs appeared for the first time on this year's Trooper with the auto trans. There was no more diesel.
1989 brought a GM 2.8 V-6 as an option with a 5 speed MUA or a European GM automatic transmission. A notable option was factory 31/10.50x15 tires on "snowflake" wheels with 4.77 gears in the diffs instead of the standard-issue 4.56's. This was standard on the short-wheelbase RS model, which came with the 2.6 and either an MUA 5-speed or the AW30-80-LE automatic.
1990 and 1991 carried over with 2.6 and 2.8 drivetrains available with manuals or autos. The RS was no longer available.
The above production dates come from an old parts manual and stresses why production dates are important when ordering something. Of course, that's not to say Isuzu couldn't have thrown a few curves in subtle differences. Also, many years have passed since these were new, so who knows what parts have been changed on the ol' warriors. This information may help determine what one needs to know before doing any repair or modifications to their Troopers, though.
Second Generation 1992-2002
Larger at 4510 pounds and plusher than its predecessor, the second-generation 4-door sport-utility wagon debuted in March 1991 in base S and luxury LS trim. Base models got a 175-horsepower (130 kW), single overhead cam (SOHC)3.2-liter V6 engine. The LS earned a dual overhead cam (DOHC) version that made 190 horsepower (142 kW). Antilock rear braking was standard; 4-wheel ABS optional, but only on the LS. A 5-speed manual gearbox was standard; electronic 4-speed automatic optional. Part-time 4-wheel drive included a floor-mounted transfer case lever and automatic-locking hubs, and was not intended for use on dry pavement.
1993: A 2-door RS wagon joined for 1993 on a wheelbase 17 inches shorter and measuring a foot shorter overall. Trim and equipment for the RS were similar to that of the 4-door LS.
1994: Four-wheel antilock braking became available on S and RS models this year, and standard on the top-of-the-line LS. Rear-wheel ABS remained standard on the lower-priced models.
1995: Trooper added dual airbags for 1995, as the 2-door wagon disappeared. All models now had four doors and Isuzu's unique 70/30 split rear doors. The new instrument panel featured stalk controls for headlights and wipers.
1996: For 1996, Troopers got a new 4WD system for shifting in and out of 4WD High while on the move. All models now had a single-cam V6 engine, but rated at 190 horsepower instead of 175.
1997: Four-wheel antilock braking was standard on all Troopers for '97.
1998: Isuzu made two important changes to the Trooper for 1998. First, they added a bigger and more-powerful V6 engine. Displacing 3.5 liters, the new DOHC V6 made 215 hp (160 kW), 25 more horsepower and 42 more pound-feet of torque than last year's 3.2-liter. European and Asian buyers could opt for a 4.0 L diesel, and other diesel engine options appeared later on, including the 4JG2 3.1 L (later superseded by the more problematic 4JX1 3.0 L). Second, they made standard a new full-time 4WD system. Called Torque-On-Demand, the system normally operated in rear-wheel drive, but automatically sent power to the front wheels when wheel slip was detected.
1999: Changes were few this year. A first-aid kit became standard and the Performance Package added fog lamps and available gold trim. This would be the last year for Acura's Trooper-clone, the SLX.
2000: Rear-wheel-drive models became available, as part of an expanded lineup. Previously, Troopers had been 4WD only. S, LS, and Limited models replaced the lone S model of '99. Troopers gained a new grille and taillights, and automatic climate control became standard. Automatic transmissions were revised with "grade logic" in an attempt to minimize gear changes on inclines. Isuzu stretched its powertrain warranty to 10 years/120,000 miles.
2001: An Anniversary Edition was added in celebration of Isuzu's 85th year.
2002: Trooper closed out its run unchanged, to be replaced for 2003 by the Chevrolet TrailBlazer-based Ascender.
Powertrain and Transmissions
Isuzu Troopers have come equipped with a wide variety of powerplants, with each successive 'generation' featuring a more powerful engine or an engine with a different fuel type.
Engine Displacement (Liters)
1st Generation 1984-1991
1.9L 4-cylinder, G200Z, gasoline,Isuzu make; carbureted;(North American market)
2.2L 4-cylinder, C223-T, turbo diesel, ISUZU make; fuel injected;(North American market)
2.3L 4-cylinder, 4ZD1, gasoline, ISUZU make; carbureted; (North American market)
2.6L 4-cylinder, 4ZE1, gasoline, ISUZU make; fuel injected; (North American market)
2.8L V6, LL2, gasoline, GM make; throttle body injected; (North American market)
Second Generation 1992-1997
3.2L V6, 6VD1, gasoline, ISUZU make; fuel injection; SOHC version in S trim level (175 to 190 horsepower depending on year), DOHC in LS and RS trim levels (190 horsepower). (North American market)
Third Generation 1998+
3.5L V6, 6VE1, gasoline, ISUZU make; fuel injected. This particular engine has gone through several design developments. Initially coming out in DOHC configuration, the last incarnation featured cutting edge 'direct injection' technology most commonly found in the ISUZU Axiom, the last ISUZU SUV model produced in the North American market (the direct injection version was never used in the Trooper). Also, the DI motor is the only interference motor out of all the 3.2/3.5's. The 3.5L engine was featured in the Trooper from 1998 through 2002 (North American market).
98-02 automatics all have the 4L30e but 00-02 have "grade logic" control
98-99 have different intake manifolds than 00-02
The powertrain computer controls differ greatly between 1999 and prior years and 2000 and newer. 1999 and older had separate engine control module (ECM) and transmission (TCM)computers, whereas 2000 and newer used a Delphi Delco Electronics powertrain control module (PCM) which combine the engine and transmission modules into one unit.
So in 2000, the Delphi PCM introduced drive by wire.
It replaced the knock sensor with a Delphi designed and calibrated ion sensing knock detection/control strategy.
Beginning in 2000 the 4L30e torque converters have GM's ECCC (Electronically Controlled Converter Clutch)which is a PWMed (Pulse Width Modulated) clutch that allows for smooth, seamless TCC (Torque Converter Clutch) applications so the driver does not feel the clutch apply. ECCC requires a different clutch material that can withstand this slippage, so ECCC torque converters cannot be exchanged with earlier non-ECCC converters.
Manual Transmissions for 1st Gen Troopers:
1984-85 MSG 4-Speed
1986-87 MSG 5-speed
1988-91 MUA 5-speed, available in 2 different bellhousings, 1 for the 2.6L 4 cyl Isuzu engine, 1 for the 2.8L V6 GM engine
Automatic Transmissions for 1st Gen Troopers:
1988-1991 Aisin-Warner A340H 4 speed automatic for 4 cyl 2.6L Isuzu engine, GM 4L30-E 4 speed automatic for 2.8L V6 GM engine
Note: All 4L30E and MUA-5 manuals had gear driven transfer cases, while the A340H had a chain driven transfer case.
History of the 4L30-E transmission.
It all starts back in the 60’s and early 70’s. Opel, the European car manufacturer starts selling their Kadett, Rekord and other models with the then popular “Trimatic” and later called “TH180” automatic transmissions.
After adding a converter clutch this trans became known as the “TH180-C”. In the USA the “TH180-C” got it’s fame under the name 3L30. Throughout this period all GM transmissions were and still are produced at the General Motors plant in Strasbourg, France. As both Opel and Buick were part of the General Motors group, Opel reached the US market through the Buick dealerships.
For reasons only GM knows they decided to add an overdrive to the 3L30. As the main case of the 3L30 could not accommodate the overdrive they were forced to put it in it’s own case and mounted it in front of the 3L30. The 4L30-E was born ! This adaptor case has it’s own valve body and even it’s own oil pan.
The 4L30-E became so popular that other car manufacturers started using it. You can find this transmissions on Isuzu Trooper and Rodeo’s, BMW’s 3 and 5 series and probably a few more brands.
The 4L30-E designation system is as follows:
4 = Four speed, L = Longitudinal, 30 = Series based on torque capacity, E = Electronic controlled.
- XS - 2-door model with the same wheelbase as the 4-door models.
- S - The S model Trooper is the base model Trooper. In the 1989-1991 models, the S trim featured black B- and C-pillars and single-tone paint.
- LS - In the 1989-1991 model year, the LS featured two-tone paint with chrome trim strips around the windshield, down the sides and, around the wheel wells, and chrome door handles. The B- and C-pillars along with the front window edging was body colored. Interior enhancements featured electric windows and locks, leatherette steering wheel, velour interior, cruise control, and folding rear seats with removable wing extensions that permitted turning the rear seats into a bed of sorts. The LS trim also included a rear wiper with washer sprayer. Ironically, many of the LS trimmed Troopers came with the MUA-5 manual transmission. These Troopers also featured a 'comfort ride suspension' meaning softer shock absorbers. The LS Troopers also came with chrome bumpers front and rear with the rear bumper featuring a ball-hitch middle section. Carpeting was included in these units as well.
- SE - The Second Generation Trooper SE was commonly referred to by dealers as the "Super Trooper" It included the two tone paint and color coordinated bumper covers and rocker cover trim panels. It had most of the available options as standard, including the huge power sunroof, leather seating, power seats, power mirrors (heated, adjustable and swing out or in by electric control) and front headlamp wiper blades and washers, to name a few.
- RS - Short wheelbase, 2-door models. While commonly available worldwide, few RS models were imported in the US. First generation RS Troopers were imported in 1989 only. Second generation Troopers were imported primarily in 1993, with a very few also in 1994 and 1995. The second gen RS is essentially a 4-door Trooper with 17 inches cut out of the middle. Almost all parts are interchangable with 4-door models, except for the "pop-out" side windows for the 2nd row passengers (as opposed to roll-down windows in the doors for the second row in 4-door models).
Early (pre 1988) Troopers had an optional rear-seat heater. The heater mounted under the passenger side front seat. Hoses ran under the floor and connected where the normal heater-core hoses do. There was a fan speed control knob next to the headlight knob on the left side of the steering column.
1st gen Troopers had optional spoilers. These mounted above the two rear doors and had two effects: 1) it helped to keep the rear windows clean by directing a flow of air across them. 2) it helped keep exhaust gases out of the truck by directing a flow of air across the back of the truck.
Pre-1988 Troopers could get a clock mounted where the cup-holder is in the center console. It was a digital clock that angled back at the driver/passenger and left a smaller change-holder for storage.
Starting in 1993 Troopers could have optional headlight washers. They had a washer nozzle and a small wiper arm under each headlight and were operated by a separate button on the dash. One push of the button would wash 3 times and wipe 4 times.
Foot rests for backseat passengers was an option in 1992-2002 Troopers. These mounted under the front seats. They were plastic boxes approx 3" tall with tops that angled backward and had a grip molded into the top. These can be removed to provide space for a CD changer or storage for other small things.
Starting in 1998, there was a compass option. The compass mounted over the rear view mirror and showed an 8 position compass, outside temperature, altitude and barometric pressure. The temp sensor was mounted behind the grille on the driver's side. Many trucks were pre-wired for this option. You can pull down the dome light and/or sunroof control panel and look for a second connector.
Repair and Tech
Troopers are pre-drilled for grab-handles on the driver side as well as the passenger side. On 1st gen Troopers there are two holes above the window where a grab handle can be mounted. By feeling through the headliner you can find the holes. 2nd gen Troopers can have two grab handles added. One on the A-Pillar and one above the side window. You'll need to remove and mark the two trim panels for square holes. Some trucks had the backs of the trim panels marked for these holes, but if your's isn't marked you can either eyeball them, measure based on the truck, or remove the passenger side trim panels and use it as a template. A detailed description of how to do this is located at this webpage 
Pre 1988 Troopers had their rear speakers mounted in the ceiling. This meant that the speakers weren't blocked when the truck was loaded with cargo. Some (maybe all) 88-91 Troopers had the upper buckets in place above the head-liner, just waiting for speakers. You should be able to see them by removing the dome light and carefully pulling down on the headliner. The pods are above the outside edges of the two rear doors.
- 2.6L won't start
- 2.6L won't stay running
- 2.6L MAF Cleaning Procedure
- 2.6L Timing Belt Procedure
- 2.6L MUA5 Bolt Pattern
- 2.6L Hose Diagrams
- 2.6L Belt Diagram
- 2.6L Misc tech info
- 2.6L Cylinder Head removal
- 2.6L O2 Sensor light reset instructions
- 2.6L Jumpering the Starter Relay
- 2.8L V6 Valve Adjustment
- Wheel Bearing Repack
- MUA 5 Speed manual loses reverse
- 3.5L Oil Consumption issues
- Check Engine Light 101
- Trooper Torsion Bar Re-indexing Procedure
- GM 60 Degree V6 Power Tips/Mods
- 1st Gen Engine Swaps
- 2nd Gen Front Suspension (US market)
When trying to find after-market parts for your Isuzu there is only a few places you can turn to.
One of the best is Independent4x. This is a 4wheel drive shop in Virgina and does a lot to help out the isuzu community. Matt, who owns the shop, is just as big of an Isuzu nut as the rest of us. So if you have any questions call him and he will help you get through them. [ http://www.independent4x.com/]
The next best place to to find parts is Calmini out of california. They have lessened their supply of isuzu stuff in the last few years, but they were still the first company to build parts for our rigs. [ http://www.pureisuzu.com/]
Replacement parts for our trucks are becoming harder and harder to find, but there are still a few good sources for them.
Jerry Lemond is one great source. Just search his name on the board and you will find his screen name. He is an ex technician trainer for Isuzu. Now that he is retired he buys out stock piles of old Isuzu parts.
Another great source is All Isuzu and Hyundai, This company sells used Isuzu parts. Consider this as a "junkyard" where they pull and inspect the parts before mailing them to you. [ http://allhyundaiisuzuparts.com/]
The Isuzu website  is a great resource for looking up part numbers and identifying parts.