FullSizeChevy.com is a community and technical resource built for full-size Chevy and GMC truck owners. Whether you own an OBS, a GMT800, a GMT900, a K2XX, a T1XX, a Squarebody, or a classic C10 — you’re in the right place. This page is your starting point for every resource we have: the forum, platform-specific guides, fix guides, mod guides, and build resources.

Join the Forum

The FullSizeChevy Forum is where owners post diagnostics, builds, mod threads, and buying advice — organized by platform, so you’re reading about your truck and not someone else’s. It’s newly rebuilt and growing, which means the threads you start now are the ones the next owner finds. If the guides below don’t answer your problem, ask there.

• OBS / GMT400 Forum (1988–1998)
• GMT800 Forum (1999–2006)
• GMT900 Forum (2007–2013)
• K2XX Forum (2014–2018)
• T1XX Forum (2019+)
• Squarebody / C10 Forum (1973–1987)
• LS Swap Forum
• General Chevy & GMC Truck Discussion

Platform Guides

Every major generation of full-size Chevy and GMC truck has its own complete guide on FullSizeChevy.com — covering common problems, engine specs, transmission info, best years to buy, and platform-specific upgrade recommendations.

• Squarebody / C10 Complete Guide (1973–1987) — rust locations, LS swap options, restoration paths, parts interchange
• OBS / GMT400 Complete Guide (1988–1998) — platform overview, known problems, build starting points
• GMT800 Complete Owner’s Guide (1999–2006) — spider injectors, 4L60E issues, best mods
• GMT900 Complete Owner’s Guide (2007–2013) — AFM issues, 5.3 tick, suspension upgrades
• K2XX Complete Guide (2014–2018) — 8-speed shudder, AFM oil consumption, leveling kits
• T1XX Complete Guide (2019–Present) — DFM, 10-speed issues, LM2 diesel, best years
• GMT800 Common Problems — every failure diagnosed
• GMT900 AFM Lifter Failure — symptoms, cost, and the permanent fix
• 4L60E Common Problems — every failure mode, and what it costs to fix

Owner Tools

• GM RPO Decoder — photograph or type the codes off your Service Parts Identification label and get the meaning for your model year
• GM RPO Codes Database — look up a single GM option code and see where each meaning came from
• Fuel Mileage Calculator — work out your real MPG or L/100 km and see how it compares against other owners running the same engine

Free, no account. They all live on the FullSizeChevy Owner Tools page.

Fix & Diagnosis Guides

Got a check engine light or a warning message? Start here — our fix guides are written by truck owners for truck owners, with real part numbers, DIY difficulty ratings, and step-by-step diagnosis protocols.

• AFM/DOD Lifter Failure — is your 5.3 ticking? diagnosis guide
• 5.3 Ticking Noise Diagnosis — cold-start protocol, AFM vs. exhaust vs. piston slap
• AFM/DFM Delete Guide — parts list, full cam and lifter swap process, tune requirements
• 4L60E 3rd Gear Slip Fix — diagnosis and rebuild decision guide
• Service StabiliTrak Fix — every cause, DTC codes, repair costs

Got a code? Every P-code guide on the site now lives in one place — the Chevy Silverado trouble code index, grouped by system: misfires, fuel trim, catalyst, EVAP, cam timing, cooling and idle.

Mod & Upgrade Guides

• Best Exhaust for 5.3 Silverado — Borla vs. MagnaFlow vs. Flowmaster ranked
• LS Swap Complete Guide — all platforms, engine selection, budget breakdown
• OBS LS Swap Wiring Harness Guide — standalone harness vendors, tach fix, fuel system
• NBS Lowering Kit Guide
• Best Tires for OBS Chevy Trucks
• Squarebody Fuel Injection Conversion
• Best Engine Swaps for Squarebody Trucks
• LS Swap Cost — how to build a real budget, not a made-up number
• Best Cold Air Intake for 5.3 Silverado — S&B vs. Volant vs. Airaid vs. K&N ranked
• How to Tune a Silverado — HP Tuners vs. Diablosport vs. dyno, AFM disable
• Best Cold Air Intake for 6.2L Silverado
• Best Exhaust for 6.2L Silverado
• Best Lift Kit for GMT800 Silverado — leveling through 6-inch, ranked
• Best Wheels for Silverado — bolt pattern, offset and fitment
• Squarebody C10 Disc Brake Conversion
• Best Tonneau Cover for Silverado — every style ranked

Buyers Guides

• Best Year Silverado to Buy — generation by generation
• Most Reliable Chevy Truck — year-by-year reliability breakdown
• Best Year GMT800 Silverado to Buy
• GMT800 Buyers Guide
• Squarebody Buyers Guide
• OBS / GMT400 Buyers Guide

Comparisons

• GMT800 vs GMT900 — which generation to buy
• 5.3L vs 6.2L — engine comparison
• Duramax vs 6.2L — diesel or gas
• Silverado vs GMC Sierra
• Silverado vs Tahoe
• Silverado vs Ford F-150 — the honest comparison
• Silverado vs RAM 1500

About FullSizeChevy.com

FullSizeChevy.com is built around one thing: helping truck owners fix, build, and get the most out of their rigs. The forum covers every generation of GM full-size truck — from Squarebody C10s to current T1XX Silverados — with its own section for each platform, plus Duramax diesel, LS swaps, and member builds. The guides on this site come from the same place: hands-on experience, real part numbers, and diagnosis that starts with the cheap stuff before you throw parts at it.

Looking for something specific? Use the search bar above or browse by platform in the navigation. If you can’t find it — ask on the forum. Post the year, engine, and what the truck is actually doing, and someone will help you work through it.

Towing Resources

• Chevy Silverado Towing Guide — capacity by generation, RPO codes, aux cooler and WD hitch recommendations
• GM Rear Axle RPO Code Guide — decode your gear ratio, G80 locker, and tow package codes
• Silverado Towing Capacity by Year