OBS – What’s That? We Describe the Description

What is an OBS? (Old Body Style or Original Body Style)

OBS refers to Chevy C/K trucks that were manufactured by General Motors between the years 1988 and 1998. Marketed under the Chevrolet and GMC brands, the C/K series included a wide range of vehicles including a truck and two SUV models. While most commonly associated with pickup trucks, the model line also included medium-duty and heavy-duty trucks. The “C” denoted a two-wheel drive; “K” denoted four-wheel drive.

General Motors released eight different versions of the C/K line for 1988: Fleetside Single Cab, Fleetside Extended Cab, Fleetside Crew Cab and Stepside Single Cab models, each in either 2WD or 4WD drivelines. Three trim levels were available for these trucks, including Cheyenne, Scottsdale and Silverado.

Represented Model Years

GMT400/480 ’88–’00 Chevrolet C/K – GMC Sierra

GMT410 ’92–’99 Chevrolet Suburban

GMT415 ’92–’94 Chevrolet Full-Size Blazer

GMT420  ’95–’00 Chevrolet Tahoe

GMT425 ’92–’99 GMC Suburban

GMT430 ’92–’00 GMC Yukon

Notable Moments in the C/K Timeline

In 1989, a Sport Equipment Package was available on either C/K 1500 Fleetside shortbed single cab model. The package featured a black grille with red outlined bow-tie emblem, black moldings outlined in red, body color front and rear bumpers, black mirrors and “SPORT” identification decals on the box and on the tailgate. There were no suspension or engine upgrades provided with any of the sport packages as this was an appearance only option.

Throttle body (TBI) fuel injection was used on ’88-’95 gas engines.

Central point injection (CPI) was used on the ’96-’00 4.3L V-6, 5.0L V-8 and 5.7L V-8.

The Work Truck (W/T) was introduced in 1988, which featured a single cab longbed with Cheyenne trim and a new grille with black bumpers. 

In 1990, Chevrolet introduced a high-performance variant of the GMT400 under the Super Sport emblem called the 454 SS. It was available only as a 2WD half-ton regular cab short box in Onyx Black with a garnet red interior. Unique exterior features included a front air dam with fog lights, special rims, decals displaying “454 SS” on the bed sides, red trim emblems, and black painted grille, bumpers and mirrors. 

The MSRP of the 1990 model was $18,295. A total of 16,953 units were sold over the four years the 454 SS was in production; 13,748 units were sold in 1990 alone. 

 The 454 SS was powered by a 454ci (7.4L) V-8 producing 230hp. A Turbo Hydra-Matic 400, 3-speed automatic transmission and 3.73 rear axle ratio added to the truck’s performance. The axle itself is unique, being a 14-bolt semi-floating unit that uses standard Chevrolet 5 on 5-inch wheels—the only factory-produced 14-bolt axle with such a wheel bolt pattern. 

 In 1991, the 4L80-E automatic transmission was added for three-quarter and one-ton trucks.

In 1991, California introduced a standard called OBD-I in order to curb vehicle emissions. All cars had to be equipped with a system that could detect engine issues and report trouble codes. Unlike the later OBD-II standard, however, OBD-I wasn’t standardized across manufacturers.

This means that an OBD-I scan tool will often work for only one make of car. In addition, the codes themselves aren’t standardized, so a Ford with the same engine issue as a Toyota might give a totally different trouble code.

In 1993 General Motors re-introduced the Sport branded trucks along with the 454 SS. The 454 SS was discontinued after the 1994 model year.

  In 1993, the 700-R4/4L60 transmission was revised with electronic controls, becoming the 4L60-E.

 The 1994 models received a new front fascia, federally mandated center high-mount stop lamp, many new exterior colors including a new two-tone option on the rocker panels, and new tire and wheel combinations.

 All 1995 models received a new interior that included a new steering wheel with the 1500s containing a driver’s-side airbag, a new dashboard containing a more centrally mounted radio, dial-operated HVAC system, and an improved gauge cluster. New front door panels and new seats were also included.

 In 1996, OBD-II became a nationwide standard and it has been used ever since. Unlike OBD-I, OBD-II equipped cars all support the same type of scanner. The trouble codes themselves have also been standardized across all manufacturers. 

 For 1996, a passenger-side-mounted third door became optional on extended cab models.

 C/K 1500 models received a passenger-side airbag for 1997 to comply with new federal regulations for light trucks.

  1997 was to be the last year the C/K Silverado would display “CHEVROLET” on the tailgate.

  In 1999, the Chevrolet Silverado became the divisional replacement for the C/K.

Chevrolet Tahoe

The Chevrolet Tahoe is a full-size SUV from General Motors. Chevrolet and GMC sold two different-sized SUVs under their Blazer/Jimmy model names through the early 1990s. This situation changed when GMC rebadged the full-size Jimmy as the Yukon in 1991. All were two-door models through 1994. 

The Chevrolet K5 Blazer name was discontinued after the 1994 model year, and the Chevrolet Tahoe was introduced in 1995 with the addition of an all-new four-door version.

The Tahoe has regularly been the bestselling full-size SUV in the United States, frequently outselling its competition by 2 to 1.

Both two-door and four-door models were produced in rear- and four-wheel drive. The two-door weighs roughly 4,500 pounds while the four-door weighs approximately 5,500 pounds. The two-door has a 6-inch shorter wheelbase than the four-door.

The standard engine was Chevrolet’s 5.7L (350ci) small-block V-8, while a turbocharged 6.5L (395ci) Detroit Diesel V-8 was available beginning in 1994.

Chevrolet Suburban

The GMT400-based Suburbans were introduced in December 1991 for the 1992 model year even though the similar pickup truck models had switched to the newer platforms in the 1988. Both 2WD and 4WD models, designated “C” and “K”, were offered, as well as half ton and three-quarter ton versions.

The GMT400 series introduced independent front suspension. The 2WD models used coil springs and 4WD models used torsion bars in the front suspension. All models used a live axle and leaf springs in the rear.

For a 1995 Suburban, 0–60 mph times were around 9.3 seconds at best. The top speed of a 1995 Suburban was governed on the engine for economy and a maximum of 98 mph could be obtained with a fuel economy of 13 mpg. 

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FREQUENTLY ASKED QUESTIONS

What are some of the sources for aftermarket and performance parts for GMT400 trucks?

Top Sources for Aftermarket and Performance Parts for GMT400 Trucks

If you’re looking to upgrade your GMT400 truck, there are several reputable sources that offer a wide range of aftermarket and performance parts. Here’s a breakdown of some of the best:

1. American Powertrain

For those interested in upgrading their transmission systems, American Powertrain provides a variety of high-performance transmission solutions.

2. Elevated Concepts, Inc.

Looking for custom and performance enhancements? Elevated Concepts, Inc. specializes in aftermarket solutions that can take your truck to the next level.

3. Gearstar

Renowned for their expertly crafted transmissions, Gearstar serves the needs of performance enthusiasts who demand reliability and superior engineering.

4. LMC Truck

From body parts to complete restoration kits, LMC Truck offers a comprehensive selection of components tailored specifically to GMT400 trucks.

5. Pro Performance

For those who want to boost their truck’s performance, Pro Performance provides a variety of parts, from suspensions to brakes, that meet the highest standards of quality.

6. QA1

If performance tuning and specialized suspension components are what you’re after, QA1 offers a range of products to enhance your truck’s handling and comfort.

7. Ridetech

To completely transform your truck’s ride quality, check out Ridetech for advanced suspension systems and air ride solutions.

8. Rock Auto

A one-stop-shop for virtually any aftermarket or replacement part you might need, Rock Auto offers a vast inventory from multiple brands, ensuring you find the right fit for your GMT400.

By exploring these trusted sources, you’ll secure top-tier aftermarket and performance parts to elevate your GMT400 truck’s capabilities.

 

How has the popularity of the GMT400 platform evolved over time?

The Evolution of the GMT400 Platform’s Popularity

From its launch, the GMT400 platform has captivated enthusiasts, gaining immediate traction in the customization scene. Early modifiers, including renowned builders, quickly saw its potential and began to innovate.

This platform didn’t just flash and fade; its appeal has remained constant over the years. What’s particularly fascinating, however, is the surge in recent attention. Over the past two years, there’s been an impressive uptick in both the volume and quality of aftermarket performance parts available.

Key Trends in GMT400 Popularity:

1. Sustained Interest: The passion for modifying GMT400 trucks has never waned. Enthusiasts have consistently valued its versatility and performance potential.
2. Recent Developments: The market has seen a flood of new, high-quality performance parts. This isn’t just about quantity; it’s the innovation and enhanced performance capabilities of these parts that are noteworthy.
3. Future Outlook: As the aftermarket continues to evolve, the GMT400 platform is poised to experience even greater levels of customization and performance upgrades.

With the expanding array of aftermarket options, the possibilities for the GMT400 seem limitless, promising exciting developments in the near future.

 

What are the future plans for Project Jake?

Future Plans for Project Jake

Looking ahead, Project Jake has a number of exciting upgrades on the horizon.

First, a brake upgrade is high on the priority list to enhance safety and performance. This update will ensure better stopping power and overall handling. Additionally, there’s a plan to swap out the current transmission for a manual one. This change will give a more engaging driving experience, adding that extra thrill of control on the road.

Suspension improvements are also in the works. Plans include possibly upgrading to coilovers for a smoother, more responsive ride. This modification will improve both comfort and handling, allowing Project Jake to tackle any terrain confidently.

Under the hood, a significant performance boost is planned. The goal is to build a clean, efficient small-block engine that delivers around 350 horsepower. Future modifications may include incorporating a tuneable port fuel injection system like Holley EFI or Edelbrock ProFlo 4, provided it complies with local regulations.

These upgrades aim to keep Project Jake not only a reliable daily driver but also a high-performance machine ready for any adventure. The vision is to blend practicality with power, ensuring this beloved pickup remains a standout on the road for years to come.

 

What maintenance and modifications have been done to Project Jake?

Maintenance and Modifications on Project Jake

Since acquiring in July 2017, a myriad of maintenance and modifications have been undertaken to keep it in top shape and enhance its performance. Here’s a detailed breakdown of the work done:

Maintenance

• Power Steering System: Replaced the power steering hoses and steering gearbox, and addressed the steering linkage.
• Front Brakes: Installed new front brake components to ensure safe stopping power.
• Air Conditioning and Wheel Cylinder: Fixed a leaking A/C compressor and a leaking rear wheel cylinder to maintain comfort and safety.
• Suspension and Steering Components: Replaced both lower ball joints and an upper A-arm bushing to improve handling and ride quality.
• Distributor and Tune-Up: Installed a new distributor due to an intermittent RPM signal and performed a comprehensive tune-up along with fluid changes to keep the engine running smoothly.
• Junkyard Finds: Scored a replacement tailgate and an improved dashboard at a budget-friendly price.

Modifications

• Suspension Upgrade: Installed a Ridetech 4/6 suspension drop kit paired with single adjustable shocks to lower the vehicle and enhance ride dynamics.
• Door Enhancements: Rebuilt the door hinges, added new door weather-stripping, and replaced damaged lock rod and door handle clips for improved functionality and aesthetics.

has been a reliable daily driver since its purchase, thanks to these meticulous maintenance efforts and thoughtful upgrades.

 

What is the history and significance of Project Jake?

History and Significance of Project Jake

Origins and Early History

In 2004, Jeff Smith came across a 1993 GMC Sierra C1500 single cab short bed pickup at a government auction, a former workhorse for Caltrans—a reminder of its utilitarian past. This wasn’t just any Sierra; Jeff’s fascination with pickups led him to purchase this specific truck, which bore the nickname “Jake.”

The Build Begins

Alongside his friend Tim Moore, who also nabbed a similar truck, they began a dual project journey. They humorously named their trucks Jake and Elwood, drawing inspiration from a famous duo. Both vehicles were destined for a transformation, each to be featured in different automotive enthusiast magazines.

The Transformation

Jeff’s Sierra had already seen over 200,000 miles of duty. However, it had a relatively new engine, marking its second life under the hood. This starting point was more than enough for Jeff, who set out to revamp Jake both cosmetically and mechanically. The makeover included:

• A fresh cowl-induction hood.
• A budget-friendly Earl Scheib paint job.
• A substantial 24-inch suspension drop.
• 17-inch aluminum Rally wheels.
• CARB-compliant shorty headers.
• A high-performance exhaust system.
• Throttle Body Injection (TBI) tweaks.
• A Hypertech chip upgrade.
• A rebuilt 4L60 transmission.

Project Jake’s Legacy

The modifications were aimed not just at aesthetics but at redefining the truck’s performance within a budget. Jeff dubbed these revamped vehicles “Blue collar bruisers,” highlighting their robust nature coupled with enhanced capabilities.

With its formidable new look and improved performance, Jake made several magazine appearances, offering readers step-by-step insights into practical, yet impressive transformations. This project underscored the accomplishment of turning a government surplus vehicle into a showpiece brimming with renewed life and charisma.

Conclusion

Project Jake stands as a testament to the potential within even the most well-worn vehicles. By focusing on strategic enhancements, Jeff Smith transformed an everyday work truck into a head-turning, high-performance machine, illustrating the power of vision, dedication, and a bit of elbow grease.

 

What manual transmission options are available for performance applications in GMT400 trucks?

Manual Transmission Options for Performance GMT400 Trucks

If you’re considering switching to a manual transmission for performance purposes in your GMT400 truck, opting for a specialized car transmission can be a more effective choice over the standard New Venture units.

Top Manual Transmission Choices

1. TKO Five-Speed Transmission
   • This transmission is excellent for a balance of performance and drivability.
   • Ideal for trucks producing moderate horsepower levels.
   • Known for its smooth shifting and reliability.
2. T56 Magnum Six-Speed Transmission
   • Suitable for high-performance applications.
   • Offers an extra gear for better fuel efficiency and enhanced performance.
   • Delivers a seamless shifting experience that transforms the truck’s driving dynamics.

Comprehensive Kit Inclusions

When upgrading, you typically need more than just the transmission itself. Comprehensive kits are available that include:

• Flywheel
• Clutch Assembly
• Hydraulic Components

These kits often provide all the necessary parts to ensure a smooth and hassle-free installation. Additionally, sourcing a clutch pedal can be challenging but is essential for the proper functionality of your manual setup.

Conclusion

Switching to one of these high-performance car transmissions will significantly enhance your GMT400 truck’s driving experience. Whether you go with the TKO five-speed for balanced performance or the T56 Magnum six-speed for ultimate power handling, these options will undoubtedly elevate your vehicle’s capabilities.

 

What are the complications of engine performance upgrades in states with strict emissions laws?

Complications of Engine Performance Upgrades in States with Strict Emissions Laws

Upgrading engine performance in states with stringent emissions laws like California can be quite challenging. Here’s why:

1. Limited Options for Certain Engines

Engines from the throttle body injected (TBI) era and the 1996-and-later Vortec 350 face particularly tough restrictions. The market offers fewer compliant parts for these older systems, making performance upgrades more complicated and often more expensive.

2. Emissions Compliance

States with strict emissions regulations enforce rigorous visual and rolling tailpipe tests. This means that any modifications must meet specific standards. While parts like CARB-compliant cylinder heads, camshafts, and headers are available, they must be correctly installed and tuned to pass these tests.

3. Tuning Difficulties

Tuning engines with OBD-1 and early OBD-II systems is especially tricky. These older models often require new PROM chips to be burned and installed into the engine control unit (ECU) or powertrain control module (PCM). This adds an extra layer of complexity and cost.

4. Availability of Tuning Solutions

Despite the challenges, there are solutions available. Flash-programmable EEPROM conversions and tuning software for OBD-1 computers can simplify the process, but they require specialized knowledge and tools. Websites like Moates.net and GearheadEFI offer valuable resources for those navigating these upgrades.

In Summary

• Limited market optionsfor specific engines.
• Strict emissions testsrequiring compliant modifications.
• Complex tuningneeds for older OBD systems.
• Specialized tools and knowledgenecessary for implementing solutions.

Upgrading your engine in a state with tough emissions laws isn’t impossible, but it demands careful planning, specialized components, and sometimes, expert assistance.

 

What suspension upgrades are available for GMT400 trucks?

Suspension Upgrades for GMT400 Trucks

If you’re looking to enhance the suspension of your GMT400 truck, there are several options available that go beyond the standard drop spindle and axle flip lowering kits.

Coilover Conversion Kits

Front and rear coilover conversion kits offer an advanced alternative. These kits not only lower your truck but also significantly improve handling and ride quality. For instance, some companies utilize unique rear upper A-arms to position the axle housing, while others prefer a torque arm and Panhard bar setup for the rear suspension.

Tubular Front A-Arms and Sway Bars

Upgrading to tubular front A-arms can make a noticeable difference. These components are often paired with larger sway bars to provide a more stable and controlled ride. Additionally, adjustable shocks allow for fine-tuning the suspension to suit different driving conditions and preferences.

Specialized Cottage Industry Options

For those looking for a more customized approach, there are specialized companies that focus solely on suspension and frame stiffening systems. These niche solutions often include enhancements like rack and pinion steering systems, specifically designed for the GMT400 platform, delivering a unique driving experience.

Summary

• Coilover Conversion Kits:Advanced handling and improved ride quality.
• Tubular Front A-Arms and Sway Bars:Enhanced stability and adjustable settings.
• Specialized Systems:Custom solutions with frame stiffening and advanced steering options.

No matter which suspension upgrade you choose, a combination of lowering, quality shocks, and high-performance tires will dramatically improve both the look and handling of your GMT400 truck.

 

What performance upgrades are available for GMT400 trucks?

Performance Upgrades Available for GMT400 Trucks

The GMT400 platform has become increasingly popular for enthusiasts looking to enhance their truck’s performance. In recent years, we’ve seen a surge in the variety and quality of aftermarket parts designed for these trucks. Here’s a detailed look at some of the top performance upgrades you can consider for your GMT400:

1. Engine Upgrades

• High-Performance Camshafts: Improve your truck’s horsepower and torque.
• Cold Air Intakes: Enhance engine efficiency by increasing air flow.
• Performance Exhaust Systems: Boost power and create a more aggressive sound.

2. Suspension Enhancements

• Lift Kits: Improve off-road capabilities and provide a more commanding view of the road.
• Lowering Kits: Offer better handling and a sleeker appearance.
• Performance Shocks and Struts: Improve ride quality and control.

3. Brake Upgrades

• Performance Brake Pads: Enhance stopping power and reduce brake fade.
• Drilled and Slotted Rotors: Improve heat dissipation and braking performance.
• Big Brake Kits: Offer the ultimate in stopping power for high-performance scenarios.

4. Transmission Mods

• Shift Kits: Provide quicker shifts and improve transmission longevity.
• Performance Clutch Kits: Handle higher power outputs more efficiently.

5. Fuel System Enhancements

• High-Flow Fuel Injectors: Offer better fuel atomization, leading to improved combustion.
• Performance Fuel Pumps: Ensure a consistent fuel supply to support engine modifications.

6. Tuning and Electronics

• ECU Reflashing: Optimize engine settings for better performance.
• Performance Chips: Quickly add horsepower and torque.
• Gauges and Monitors: Keep an eye on vital statistics to ensure optimal performance.

The Growing Market

The evolution of aftermarket performance parts for GMT400 trucks is fascinating. From improving overall power to fine-tuning handling and braking, the options are vast and continually expanding.

With the right upgrades, your GMT400 can achieve remarkable gains in performance, making it a beast both on-road and off-road.

 

What aftermarket options are available for addressing rust issues on GMT400 trucks?

Aftermarket Options for Addressing Rust Issues on GMT400 Trucks

Dealing with rust issues on GMT400 trucks? There’s an array of aftermarket solutions available to restore these classic vehicles to their former glory.

For starters, you can replace rusted components with brand-new sheet metal sourced from various restoration companies and truck specialists. Options include:

• Cab Corners and Rocker Panels:Essential for tackling rust in critical areas.
• Complete Doors and Bedsides:Perfect for more comprehensive repairs.
• Floors, Fenders, Hoods, and Tailgates:Ensuring every part of your truck looks and performs like new.

What’s great is that these components are often surprisingly affordable, making it feasible to maintain your truck’s condition without breaking the bank.

Why Choose Aftermarket Components?

Using aftermarket parts allows for high customization and ensures compatibility with your specific truck model. These parts can often be more accessible and cost-effective than original manufacturer parts.

By investing in quality aftermarket parts, you’ll not only address rust issues but also enhance the overall aesthetic and functionality of your GMT400 truck.

 

Why are the brakes on the GMT400 trucks considered insufficient?

Why Are the Brakes on GMT400 Trucks Considered Insufficient?

The brakes on GMT400 trucks have garnered criticism for several reasons, particularly from those who require reliable stopping power for towing, hauling, or spirited driving.

Brake Size

The front brakes come with relatively small 11-inch or 11.25-inch rotors paired with single-piston calipers. The rear brakes aren’t much better, offering 10-inch or 11-inch drums. This size limitation means they quickly become inadequate under heavy load or intense driving conditions.

Inefficiency Under Load

For tasks like towing or hauling, the standard braking system simply can’t keep up. Drivers often find themselves wishing for larger, more capable brakes, especially in situations where quick and reliable stopping is crucial.

Brake Feel and Performance

Adding to the frustration, the Quick Take Up brake master cylinder combined with low-drag brake calipers results in a brake pedal feel that many describe as “mushy.” The long pedal travel distance can be disconcerting, giving drivers less confidence in the vehicle’s braking capabilities.

Summing It Up

• Small Front Rotors: Only 11-inch or 11.25-inch in diameter.
• Rear Drums: Limited to 10-inch or 11-inch sizes.
• Performance Issues: Struggles with towing, hauling, and spirited driving.
• Brake Pedal Feel: Mushy with long travel due to the Quick Take Up system and low-drag calipers.

Given these points, it’s clear why the stock braking system on GMT400 trucks leaves much to be desired. For those requiring more robust performance, upgrading to larger, more efficient brakes is often considered a necessary improvement.

 

What issues are associated with the clear coat on GMT400 trucks?

Common Clear Coat Issues on GMT400 Trucks

The GMT400 series of trucks, produced during the late ’80s and ’90s, often face challenges related to their clear coat. These vehicles are particularly prone to oxidation, a process where the clear coat deteriorates due to prolonged exposure to the sun. Over time, this exposure can lead to visible wear and damage.

Here are key issues you might encounter:

• Sun Damage:The clear coat is susceptible to ultraviolet (UV) radiation, leading to fading and discoloration.
• Peeling:Over time, the clear coat may start to peel off, revealing the underlying paint and significantly affecting the vehicle’s appearance.
• Material Degradation:The clear coat can begin to break down due to the paint materials used during that era. Manufacturers were adapting to new regulations around paint emissions, which resulted in some compromises on durability.

Addressing the Issues

To mitigate these problems, regular maintenance and specific treatments can help:

1. Frequent Waxing:Apply wax regularly to provide an additional layer of protection against UV rays.
2. Use of Sealants:High-quality paint sealants can offer longer-lasting protection and delay the oxidation process.
3. Shaded Parking:Whenever possible, park your vehicle in shaded areas to minimize direct sun exposure.

Keeping these points in mind will help maintain the appearance and longevity of your GMT400 truck’s clear coat.

 

What are some common problems associated with the GMT400 series trucks?

Common Problems Associated with GMT400 Series Trucks

When it comes to the GMT400 series trucks, owners often encounter a few recurring issues. Here’s a rundown of the most common problems:

Rust and Corrosion

Rust is a notorious issue for these trucks. Even though they were touted as having good corrosion protection, this claim was only valid when comparing them to their predecessors. Key areas prone to rust include:

• Cab corners
• Rocker panels
• Wheel arches

This is especially true for trucks in wet and snowy climates, where moisture accelerates the rusting process.

Dashboard Deterioration

The dashboard design saw a significant overhaul in 1995, which improved its durability. However, earlier models suffer from:

• Cracking
• Disintegration due to sun damage

While the later dashboards offer better resistance, it’s a common point of concern for those with older models.

Upholstery Wear and Tear

Interior materials vary in longevity. Generally:

• Cloth upholstery holds up better over time
• Leather seats are more likely to show wear and tear

This difference is important to consider if you value your truck’s interior condition.

Clear Coat Issues

Like many American vehicles from the ’80s and ’90s, the GMT400 series struggles with clear coat problems. Sun exposure tends to:

• Oxidize the clear coat
• Cause peeling

This typically results from manufacturers adapting to new paint emission regulations, which affected the durability of the paint.

Brake System Limitations

The brake system is another common complaint. GMT400 trucks come with:

• 11×1 or 1.25-inch front rotors with single-piston calipers
• 10- or 11-inch rear drums

These brakes often prove insufficient for towing, hauling, or spirited driving. Issues include:

• A mushy pedal feel
• Extended pedal travel

The system’s Quick Take-Up master cylinder and low-drag calipers sound good on paper but don’t always deliver the best performance.

Conclusion

While the GMT400 series trucks are celebrated for their reliability, these common issues warrant attention from any prospective or current owner. Addressing rust, interior wear, paint degradation, and brake performance can help maintain the truck’s value and functionality.

 

How Did the GMT400 Series Trucks Differ From Their Predecessors?

The GMT400 series introduced several groundbreaking changes that set it apart from earlier models.

First and foremost, the GMT400 series was the debut lineup to feature independent front suspension on its 4×4 models. This advanced design replaced the older solid front axle and leaf springs with torsion bars and CV joints.

Key Differences:

1. Independent Front Suspension:
   • Old Models:Solid front axle and leaf springs.
   • GMT400:Torsion bars and CV joints.
2. Shift-on-the-Fly Four-Wheel Drive:
   • The previous manual locking hubs were substituted with a more convenient shift-on-the-fly system, enhancing ease of use and performance.
3. Enhanced Safety Features:
   • The frame was widened to allow the fuel tank to be positioned inboard, addressing safety issues associated with the side-saddle gas tanks of earlier trucks.

These modifications not only improved the driving experience but also significantly boosted the safety and convenience of the GMT400 series, marking a notable evolution from its predecessors.

 

What are some transmission upgrade options for GMT400 trucks?

In 1991, the 4L80-E automatic transmission was added for three-quarter and one-ton trucks.

In 1993, the 700-R4/4L60 transmission was revised with electronic controls, becoming the 4L60-E.

For those considering manual transmission upgrades, several options were available during the production of GMT400 trucks. The half-ton pickups typically came with HM290/5LM60 or NV3550 five-speed transmissions, generally rated to handle around 300 lb-ft of torque. Meanwhile, the more robust NV4500 was an option for the 2500 and 3500 series trucks. These transmissions were designed specifically for these trucks, featuring a steeper first gear and larger RPM drops between shifts.

If you’re looking to enhance performance by switching from an automatic to a manual transmission, opting for a “car” transmission might be more beneficial. Kits are available that offer TKO five-speed or T56 Magnum six-speed options, depending on your power requirements. These kits often include the necessary flywheel, clutch assembly, and hydraulic components, and can assist in sourcing a clutch pedal, which can be hard to find.

These smoother-shifting transmissions can significantly transform your truck’s driving experience, providing a more engaging and responsive feel behind the wheel.

 

How did the redesign of the dashboard in 1995 improve the GMT400 trucks?

All 1995 models received a new interior that included a new steering wheel with the 1500s containing a driver’s-side airbag, a new dashboard containing a more centrally mounted radio, dial-operated HVAC system, and an improved gauge cluster. New front door panels and new seats were also included.

The redesign of the dashboard in 1995 marked a significant improvement over the earlier models. The earlier versions used hard plastics that were prone to cracking or disintegrating completely due to sun damage. The new design utilized materials that were much more resistant to these issues, ensuring greater durability and longevity.

Additionally, the cloth upholstery in the updated models fared better over time compared to the leather seats, adding another layer of quality to the interior.

The combination of these upgrades made the 1995 interior not just more functional but also more durable, addressing common issues faced by owners of earlier models.

 

What innovations were introduced with the GMT400 series?

“The GMT400 series introduced independent front suspension. The 2WD models used coil springs and 4WD models used torsion bars in the front suspension. All models used a live axle and leaf springs in the rear.”

Notably, the GMT400 was more than just a visual update from its predecessors. This series marked the first use of independent front suspension on 4×4 models, with torsion bars and CV joints replacing the solid front axle and leaf springs of the older trucks.

Another significant innovation was the introduction of shift on the fly four-wheel drive, eliminating the need for manually locking hubs. This new feature made transitioning between two-wheel and four-wheel drive seamless and more convenient.

In addition to these mechanical upgrades, the GMT400 addressed safety concerns by widening the frame to move the fuel tank inboard. This change mitigated risks associated with the previous generation’s side-saddle gas tanks, enhancing overall safety for drivers and passengers.

 

What are the OBS Chevys, and why are they gaining popularity?

OBS – What’s That? We Describe the Description

What is an OBS? (Old Body Style or Original Body Style)

OBS refers to Chevy C/K trucks that were manufactured by General Motors between the years 1988 and 1998. Marketed under the Chevrolet and GMC brands, the C/K series included a wide range of vehicles, including a truck and two SUV models. While most commonly associated with pickup trucks, the model line also included medium-duty and heavy-duty trucks. The “C” denoted a two-wheel drive; “K” denoted four-wheel drive.

Historical Context and Evolution

The OBS label was assigned to the GMT400 once the GMT800 (model years 1999-2006) were introduced, and that generation is known as NBS, or ‘new body style.’ In SUV form (Tahoe, Yukon, and Suburban), the GMT400 continued through the 2000 model year and even into 2002 for the one-ton C3500 pickups.

Design and Technical Innovations

Outwardly, the GMT400 represented a significant visual departure from the square body trucks it replaced, featuring a sleek, aerodynamic body. More noteworthy changes, however, could be found underneath. This was the first GM pickup to feature an independent front suspension on their 4×4 models, utilizing torsion bars and CV joints to replace the solid front axle and leaf springs of the previous generation.

Key Innovations Include:

• Independent Front Suspension:Enhanced handling and ride comfort.
• Shift on the Fly Four-Wheel Drive:Replaced the manually locking hubs of the previous generation, providing more convenience.
• Widened Frame:Moved the fuel tank inboard, addressing safety concerns about the older truck’s side-saddle gas tanks.

Why Are They Gaining Popularity?

These trucks are not just cherished for their nostalgic value but also for the practical and innovative improvements they introduced. The combination of visual appeal and mechanical advancements makes them highly sought after by both collectors and enthusiasts. Whether for restoration projects or daily use, the OBS Chevys offer a blend of classic design and forward-thinking engineering.