OBS / GMT400 Chevy & GMC Trucks (1988–1998)
The OBS — “old body style,” the GMT400 platform — is the 1988–1998 Chevy and GMC C/K trucks and SUVs that a lot of people call the best-looking full-size GM ever made. Simple, fixable, and getting more valuable every year. This is the hub for buying, fixing, swapping and building them. Other eras: the Squarebody (1973–1987) and GMT800 (1999–2006) hubs, or the LS Swap hub.
Latest OBS / GMT400 Content
Start here: buying & identifying an OBS
- OBS Chevy Buyer’s Guide for Smart Purchases
- What Is an OBS Chevy? The Real Meaning
- What Years Are OBS Chevy Trucks?
- How to Identify GMT400 Years
- OBS Chevy Market Trends
Engines, drivetrain & LS swaps
- GMT400 Engine Options That Actually Make Sense
- OBS Chevy LS Swap Wiring Harness Guide
- GMT400 Parts Interchange Guide
Electrical, AC & real-world fixes
From 1996 an OBS runs OBD-II, so a scanner gives you a real code instead of a flashing lamp count. The Silverado trouble code index covers what those codes mean and what actually fixes them.- OBS Chevy Wiring Guide for Real-World Fixes
- OBS Chevy AC Not Working? Start Here
- OBS / GMT400 4-Hi Headlight Mod — discuss wiring methods on the forum
- Best OBS Chevy Headlights
- OBS Chevy Door Hinge Repair
- OBS / GMT400 Lighting Tech Pack, 1988–1998 (forum reference)
- OBS Door Handle Rod Clips: Part Numbers & the Handle-Won’t-Open Fix
- OBS Headlight Conversion: Sealed Beam to Composite (forum guide)
- GMT400 Torque Specs (1988–1998): Validated Quick Reference
Interior & comfort
- GMT400 Interior Swap Guide
- OBS Chevy Bench Seat Swap
- OBS Escalade/Denali Center Console Swap (forum guide)
- OBS HVAC Knob Swap — Express/Savana Knobs (forum guide)
- OBS Headlight Knob Swap — Express/Savana Knobs (forum guide)
- 96–98 OBS Interior LED Upgrade (forum guide)
- Add Cupholders to a 94–98 OBS Console — CD-Changer Delete (forum guide)
Wheels, tires & suspension
- Best Tires for OBS Chevy Trucks
- OBS Chevy Wheel Fitment Explained
- Can a GMT400 Fit 33s?
- GMT400 Suspension Upgrade Ideas
- GMT400 Tow Mirror Upgrade
Paint, body & mods
- How to Restore OBS Chevy Paint Right
- OBS Chevy Paint Codes Explained
- 9 Best OBS Chevy Mods That Actually Matter
- OBS Chevy Truck Build Planning Guide
Owner tools for your OBS
Free, no sign-up. Worth running before you order parts for a 1988–1998 truck.- GM RPO Decoder — type the option codes off your glove box sticker, or photograph the label and let the page read it. On a truck this age the sticker is often the only honest record of how it was built.
- GM RPO Code Database — every option code we hold, searchable by code or by plain description, and filterable to your model year.
- MPG Calculator — miles, gallons, engine. You get your number and where it sits against everyone else running the same engine.
Join the OBS discussion
OBS / GMT400 Gear
Shop all OBS / GMT400 gear →
Keep It Full Size | OBS Can Cooler$8.23
Keep It Full Size OBS Chevy Truck Poster | Classic 88-98 Chevy Pickup Garage Wall Art | Full Size Truck Enthusiast Decor Price range: $34.18 through $112.27
OBS GMT400 Chevy Truck T-Shirt – Keep It Full Size OBS (1988-1998 Silverado) | Keep It Full Size Price range: $28.86 through $35.61
OBS GMT400 Chevy Truck T-Shirt – Green Neon City Sunset (1988-1998 Silverado) | OBS Legends Price range: $28.86 through $35.61
OBS GMT400 Chevy Truck T-Shirt – Green Graffiti Neon II (1988-1998 Silverado) | OBS Legends Price range: $28.86 through $35.61
Keep It Fullsize | OBS Chevy Vinyl Sticker Price range: $1.98 through $12.57
OBS GMT400 Chevy Truck T-Shirt – Full Size or Nothing (1988-1998 Silverado) | Fullsize Monster Truck Series Price range: $28.86 through $35.61
OBS GMT400 Chevy Truck T-Shirt – Neon Outline American Flag (1988-1998 Silverado) | OBS Legends Price range: $28.86 through $35.61
OBS GMT400 Chevy Truck T-Shirt – Black Desert Road Sunset (1988-1998 Silverado) | OBS Legends Price range: $28.86 through $35.61
OBS GMT400 Chevy Truck T-Shirt – Blue Desert Sunset & Cactus (1988-1998 Silverado) | OBS Legends Price range: $28.86 through $35.61
OBS GMT400 Chevy Truck T-Shirt – Bowtie (1988-1998 Silverado) | OBS or Die Price range: $28.86 through $35.61
OBS GMT400 Chevy Truck T-Shirt – City & Palms (1988-1998 Silverado) | GMT400 Crew Price range: $28.86 through $35.61
OBS GMT400 Chevy Truck T-Shirt – Orange Route 66 Gas Station (1988-1998 Silverado) | OBS Legends Price range: $28.86 through $35.61
OBS GMT400 Chevy Truck Hat – Bowtie, Embroidered (1988-1998 Silverado) | OBS or Die$42.61
OBS GMT400 Chevy Truck T-Shirt – Night City (1988-1998 Silverado) | GMT400 Crew Price range: $28.86 through $35.61
Keep It Full Size | OBS Coffee Mug — Classic Truck Lover Gift (11/15oz) Price range: $10.70 through $14.14
Talk OBS / GMT400 with other owners
Post your truck, your build, or the problem you are chasing. Real OBS / GMT400 owners in the FullSizeChevy forum can share what actually worked on theirs.
Open the GMT400 Forum →TECHNICAL INFORMATION NOTICE
Repair, modification, compatibility and specification information on FullSizeChevy.com is provided for general informational purposes only. Always verify procedures, torque values, parts fitment and safety requirements for your exact vehicle using factory service information before performing work. Repairs and modifications are performed at your own risk.