feat: Add comprehensive vehicle specs and VIN decoder reference

- Add detailed VIN decoder breakdown with all 17 characters explained
- Add complete vehicle specifications table (engine, dimensions, weights, capacities)
- Include VIN decoder URL pattern for quick reference
- Engine: 5.7L V8 L31 Vortec (258 HP, 330 lb-ft)
- Transmission: 4L80-E heavy-duty 4-speed automatic
- Suspension, brakes, tires, and all key specs documented

README.md

@@ -8,11 +8,52 @@
 |-------|-------|
 | **Year/Make/Model** | 2002 Chevrolet Express 3500 |
 | **VIN** | 1GAHG39R821226228 |
-| **Engine** | 5.7L V8 |
+| **Engine** | 5.7L V8 (L31 Vortec) |
+| **Horsepower** | 258 HP @ 4,600 rpm |
+| **Torque** | 330 lb-ft @ 2,800 rpm |
+| **Transmission** | 4-speed Automatic (4L80-E heavy-duty) |
+| **Drivetrain** | RWD |
+| **Fuel Capacity** | 31 gallons |
+| **Curb Weight** | 4,849 lbs |
+| **Max Towing Capacity** | 8,000 lbs |
+| **Wheelbase** | 135.0 inches (standard) / 155 inches (extended) |
+| **Overall Length** | 218.8 inches (standard) / 238.8 inches (extended) |
+| **Overall Width** | 79.2-79.4 inches |
+| **Overall Height** | 82.5-82.8 inches |
+| **Tire Size** | P245/75R16 |
+| **Rim Size** | 16" steel |
+| **Valve Configuration** | OHV (16-valve) |
+| **Compression Ratio** | 9.4:1 |
+| **Engine Oil Capacity** | 5.1 quarts (5W-30) |
+| **Brakes (Front)** | Dual Hydraulic Disc |
+| **Brakes (Rear)** | Dual Drum Brakes |
+| **Front Suspension** | MacPherson Strut with Double Tube dampers |
+| **Rear Suspension** | Multi-Link Coil Springs with Double Tube dampers |
+| **Headlight Bulb** | 9007 Halogen |
 | **Date Started** | 2026-03-20 |
 
 ---
 
+## 🔍 VIN Decoder Reference
+
+**VIN Format:** `1GAHG39R821226228`  
+**Decoder URL Pattern:** `https://www.decodethis.com/vin/[VIN]`
+
+**VIN Breakdown:**
+- **1** = United States (Manufacturer)
+- **G** = General Motors
+- **A** = Chevy
+- **H** = GVWR Range 9001-10000 lbs
+- **G3** = Express 3500 (1-ton)
+- **9** = Brake System - Hydraulic
+- **R** = 5.7L V8 Gasoline Engine (8th digit = engine code)
+- **8** = Check Digit
+- **2** = Model Year 2002
+- **1** = Assembly Plant
+- **226228** = Production Sequence Number
+
+---
+
 ## 📋 Project Overview
 
 This repository tracks all maintenance, repairs, and issues for the 2002 Chevy Express 3500. Each subfolder represents a specific issue or maintenance task with its own progress tracking.