2025-2026 Chevrolet GMC 1500 Trail Boss & AT4 4” Suspension Big Lift Kit

## Product Summary

| Field | Details |
|—|—|
| Brand | ReadyLIFT |
| Part Number | RL4435425 |
| Fitment Type | Performance/Custom |
| Adjustable | No |
| Performance Part | Yes |
| Country of Origin | United States |
| Vehicle Placement | Left, Right, Front, Rear |
| Lift | 4-inch Big Lift Kit |
| Warranty | ReadyGuard Powertrain Warranty |

## Compatible Vehicles

| Year | Make | Model | Trim | Engine |
|—|—|—|—|—|
| 2025–2026 | Chevrolet | Silverado 1500 | Custom Trail Boss Crew Cab | 2.7L I4 Turbo Gas |
| 2025–2026 | Chevrolet | Silverado 1500 | Custom Trail Boss Crew Cab | 3.0L I6 Turbo Diesel |
| 2025–2026 | Chevrolet | Silverado 1500 | Custom Trail Boss Crew Cab | 5.3L V8 Gas |
| 2025–2026 | Chevrolet | Silverado 1500 | LT Trail Boss Crew Cab | 2.7L I4 Turbo Gas |
| 2025–2026 | Chevrolet | Silverado 1500 | LT Trail Boss Crew Cab | 3.0L I6 Turbo Diesel |
| 2025–2026 | Chevrolet | Silverado 1500 | LT Trail Boss Crew Cab | 5.3L V8 Gas |
| 2025–2026 | Chevrolet | Silverado 1500 | LT Trail Boss Crew Cab | 6.2L V8 Gas |
| 2025–2026 | GMC | Sierra 1500 | AT4 Crew Cab | 3.0L I6 Turbo Diesel |
| 2025–2026 | GMC | Sierra 1500 | AT4 Crew Cab | 6.2L V8 Gas |

## Kit Includes

| Component | Included |
|—|—|
| Front/rear cross members | Yes |
| Full-width front skid plate | Yes |
| Differential drop brackets | Yes |
| Top-mount strut extensions | Yes |
| Lower strut pre-load spacers | Yes |
| Rear lift blocks | Yes |
| Rear shock extensions | Yes |
| Sway-bar drop brackets | Yes |
| Cast-iron lift knuckles | Yes |
| Hardware & installation instructions | Yes |

## Important Fitment Notes

– **Not for diesel applications**, despite the compatibility table listing diesel engines.
– **Not compatible with rear mono-leaf springs.**
– **Single Cab configuration has not been validated** for fitment or drivability.
– Use of **Auto 4 Hi is not recommended**.
– An **18-inch wheel is not recommended** because of fitment issues.
– An **18×9 wheel with 0 mm offset or higher does not work**.
– Recommended maximum tire setup without trimming: **20×9 wheel, 0 offset, 35×12.50 tire**.
– Larger wheel/tire combinations may require trimming of the front valance, front/rear felt liner edges, and mud-flap/wheel-well areas.

## Answer

**This is ReadyLIFT part RL4435425, a 4-inch lift kit designed for 2025–2026 Chevrolet Silverado 1500 Trail Boss and GMC Sierra 1500 AT4 Crew Cab 4WD trucks.**

**The key issue is the diesel compatibility conflict:** the supplied vehicle-compatibility table lists the **3.0L Duramax diesel**, but the seller’s own description explicitly states **“Not for use on Diesel motor applications.”** Therefore, based on the information provided, **do not consider this kit compatible with the 3.0L diesel**, even though the compatibility table says it is.

For gas-powered trucks, the listed compatible configurations are:
– 2.7L Turbo I4
– 5.3L V8
– 6.2L V8

The kit provides approximately **4 inches of lift** using front strut extensions, differential-drop components, lift knuckles, rear lift blocks, shock extensions, sway-bar brackets, and heavy-duty crossmembers/skid plate.