Guide to GM OBS Truck Parts Part 1 – Suspension, Steering and Brakes
Has any other model of vehicle gained more popularity in the last few years than the 1988-98 GM truck platform? These trucks, generally referred to as the OBS truck platform, have seen a rapid growth in popularity, following right on the heels of the GM squarebody boom that came before, which was itself an outgrowth of the popularity of 1967-72 Chevy and GMC models. All trucks, especially those from the 1960s through the 1980s, have captured a lot of attention in recent years, but the OBS models are certainly leading the charge right now.
So, what does the OBS acronym stand for? Believe it or not, it means Old Body Style. It makes almost no sense, but history shows that the ’88–’98 used an internal GM code of GMT400 which was replaced in 1999 by the GMT800, thus making the previous model the Old Body Style. It kinda make sense.
Whether the name seems fitting or not, you cannot deny the meteoric rise in popularity of these trucks and SUVs! The OBS truck era has helped introduce the hot rodding hobby to thousands of younger people who are now modifying, cruising, and working on their own trucks – and attending a lot of shows!
These trucks have also provided a completely new platform for the performance aftermarket to jump into and there are so many new restoration and custom components available for OBS owners, we decided to break our Guide to GM OBS Truck Parts into two segments starting with suspension, steering and brakes. Watch for part two of this Guide, featuring anything not bolted under the truck, to hit soon!
CPP
Xtreme Drop Spindles
How low do you plan on dropping your OBS truck? Classic Performance Products (CPP) now offers its Xtreme Drop Spindle Kit designed specifically for 1988-98 C1500 trucks. It’s engineered for extreme lowering applications and to handle the demands of 20-inch or larger wheels. The 2.5-inch drop spindles precisely integrate with factory ball joints and tie rods, ensuring easy installation while optimizing suspension geometry.
At the core of this design is a reinforced sealed bearing hub assembly, virtually eliminating the axle pin flex common on traditional spindles. This results in improved durability, braking performance, and a smoother ride. The spindles are compatible with CPP’s Big Brake Kits along with their Totally Tubular control arms.
Speedtech Performance
Extreme Chassis
SpeedtechLooking to start with an all-new foundation for your OBS truck build? Check out the ExtReme Chassis from Speedtech Performance. This chassis is designed to transform your OBS truck into a high-performance hauling machine with improved rigidity and modern handling characteristics.
The ExtReme Chassis has two IRS options: a Low Mount Shock or High Mount Cantilevered Shock that delivers a significantly increased rear shock motion ratio which improves rear grip with lower spring rates. The chassis offers fully adjustable rear wheel alignment and incorporates exclusive forged aluminum spindles. Up front there is corrected Ackerman geometry for better cornering grip and an optimized scrub radius for larger wheels along with a three-piece chromoly tubular splined sway bar.
Borgeson Universal
New Steering Response
Borgeson Universal recently introduced a new power steering box for GM OBS trucks that has a quicker turning ratio of 12.7:1 versus the stock ratio of 14:1 or the factory 16/13:1 variable-ratio unit. This means that for every 12.7-degrees of steering wheel movement, the output shaft rotates 1-degree, which means reduced lock-to-lock turning effort.
For two-wheel drive ’88–’96 OBS fans, Borgeson has you covered as their new box is a direct bolt-in for those models. The box is a touch shorter in length than the factory unit but installs with the same three mounting points and connects directly to the factory steering shaft. The OEM fluid lines and power steering pitman arm all bolt back in place.
QA1
Front to Back Suspensions
QA1 offers a full range of suspension upgrades for your OBS truck that will immediately improve the handling and ride quality of your truck. Each of the company’s components provide upgraded geometry and are compatible with modern tires and wheel sizes.
QA1’s Level 2 and 3 coil-over kits deliver adjustable ride height and improved control, with Level 2 focusing on a bolt-in design for street cruising and Level 3 providing adjustability and performance for spirited driving. Tubular control arms optimize camber gain and caster while the torque arm rear suspension eliminates leaf springs, reducing axle wrap while improving traction, with sway bars to enhance cornering capability. Together, these upgrades transform OBS trucks into well-balanced performers for the street or track.
Wilwood
Big Rear Disc Kit
By today’s standards, it’s hard to believe that OBS trucks were still built with rear drum brakes. Looking back 30-plus years, it makes sense, but today drums just don’t live up to enthusiast expectations. Wilwood offers easy-to-install big brake rear drum-to-disc conversions for the C1500 Silverado, Sierra, and similar SUVs that bolt-in and deliver improved stopping power while improving the look of your truck.
The Wilwood kit is based on the company’s motorsports-proven AERO4R caliper and 14-inch Spec 37 rotor providing increased clamping force, better thermal capacity, and improved pedal feel for all-around more confident braking performance. These brake kits are designed to complement and be compatible with Wilwood front disc kits, factory ABS, and OE master cylinders.
Belltech
Drop Spindles for the Ride
Belltech was in the thick of the original sport truck movement, helping enthusiasts get their new trucks lowered right – and they’re still going strong! The company offer a 3-inch drop spindle that makes lowering your truck easy without sacrificing ride quality or comfort while delivering modernized handling.
Each Belltech spindle is forged from OEM-grade ductile iron for superior strength and is powder coated for longevity. The spindle maintains the factory track width for a tighter turn radius and works with the OEM brakes and 18-inch or larger wheels. Your truck will ride on an improved roll center with increased anti-dive and overall improved cruising.
Roadster Shop
Go Low Like a Pro
Sport truck history has shown that getting your truck obscenely low usually meant having to raise the bed. The chassis pros at Roadster Shop set out to change that with their OBS Low-Pro Chassis. That’s right, you can air-out your OBS to the ground and retain the OEM bed floor height thanks to RS’s unique low-profile trailing arm IRS system.
Tightly packaged beneath the factory bed structure sits an innovative link system supporting a trailing arm with an air spring and cantilevered shock setup. This system delivers the most shock travel combined with accurate valving to produce incredible ride quality. New front suspension geometry, specifically designed for the OBS platform, allows the use of the largest aftermarket wheel and tire packages.
Auto Metal Direct
Rad and Cab Bushing Kits
Here are a couple replacement parts from Auto Metal Direct that will help many OBS truck owners to restore the ride quality and structural integrity their truck. AMD now offers a premium Cab Mount Kit and Radiator Support Bushing Kit, two important components that are likely overdue to be replaced on your truck.
Both bushing kits are made from high-quality materials for durability and designed for precise factory fitment to replace worn, cracked, or deteriorated bushings. Once installed, you’ll immediately notice a tighter ride with less cab movement and reduced vibration. Both bushing kits will help improve panel alignment and are one more step in renewing your OBS for years to come.
Baer
Bear Claw Braking
Looking to upgrade your braking performance while improving the look of those ugly factory rotors? Baer has the answer with their direct-fit Baer Claw rotors. The new rotors are slotted and drilled, allowing gasses and dust to escape during braking. Plus, the vane structure of the rotor provides improved cooling and durability, which adds up to better braking consistency and performance.
There is also no denying the improved aesthetics that the Baer Claw rotors provide behind larger diameter open wheels. The stock calipers can be retained, but it’s recommended to bolt in a set of Baer’s exclusive Claw brake pads. These effective pads feature a ceramic compound formulated to provide long-lasting performance with minimum noise and dust.
GSI Machine and Fabrication
Notch it Down
To notch or not to notch? That is a question most truck owners face when lowering their OBS truck. Chances are you’re going to end up C-nothing the frame rails in your OBS to obtain more clearance between the axle and the frame rails. It’s a common practice and GSI Machine and Fabrication has you covered with their bolt-in C-Notch Kit.
GSI sweated the details to deliver a bolt-in C-Notch Kit for builders or DIYers. The precision-formed steel notch assemblies measure 25.5-inches long, are powder coated semi-gloss black, and can be bolted in place using the supplied grade-8 1/2-inch hardware. GSI also offers a complete axle flip kit and shock relocation brackets to help finish the job right.
RideTech
Gripping the Street
Ridetech’s StreetGRIP system is a complete suspension package with parts designed to work together while giving your truck an ideal 4- and 6-inch drop with improved handling and ride characteristics. The rear system starts with an axle flip kit along with RideTech’s unique heavy-duty bolt-in C-notch brackets. Shock extenders are supplied for Ridetech monotube shocks with rebound adjustments so you can dial-in ride quality.
Dual-rate coil springs are used on the front corners working in conjunction with drop spindles to achieve the perfect stance while maintaining correct geometry and alignment. A larger sway bar improves cornering stability while their custom-valved HQ Series monotube shocks provide the ultimate in ride quality and handling.
Choppin’ Block Chassis Products
Choppin’ Control Arms
The crew at Choppin’ Block Chassis Products understands what it takes to achieve the right look and the right ride when it comes to you OBS truck. For anyone moving toward a coil-over suspension system, the company’s Performance Control Arm Set will get you headed in the right direction.
Constructed of DOM tubing and fully TIG welded, CB’s arms are narrowed from stock to provide more wheel clearance and feature increased caster for better-weighted steering and center return. The arms are compatible with all standard-mount coil-over shocks and are supplied with polyurethane bushings, Moog ball joints, and finished in a durable black powder coating. Check out CB’s Performance Rear kit to obtain a perfect 5/7 drop.
