FOX 987-24-025 Perf 2.5 IFP HTO Rear Shock 20-25 Silverado/Sierra 2500/3500 6.5"

Vehicle Fitment

• 2020-2025 Chevrolet Silverado 2500 HD (4WD; all cab and bed configurations; gas and diesel) - Confirmed fitment; rear shock
• 2020-2025 Chevrolet Silverado 3500 HD (4WD; all cab and bed configurations; gas and diesel) - Confirmed fitment; rear shock
• 2020-2025 GMC Sierra 2500 HD (4WD; all cab and bed configurations; gas and diesel) - Confirmed fitment; rear shock
• 2020-2025 GMC Sierra 3500 HD (4WD; all cab and bed configurations; gas and diesel) - Confirmed fitment; rear shock
• Designed for vehicles with 6.5" of rear lift. This is a single-lift-height-specific shock - confirm your rear lift is at or matches the 6.5" specification before ordering. FOX offers companion 987-series rear variants for other lift ranges on the same platform: 987-24-009 (0-1" lift), 987-24-011 (1.5-2.5" lift), and 987-24-035 (4-6" lift).
• 4WD models only.

Application Notes

• The 987-24-025 is the rear companion to the 987-24-024 front shock (2020-2025 Silverado/Sierra 2500/3500 HD, 6.5" front lift). For a complete front and rear 6.5" lift shock package on the 2020-2025 GM HD platform, both the 987-24-024 (front) and 987-24-025 (rear) are required.
• The 2020-2025 Silverado/Sierra 2500/3500 HD uses a solid rear axle with multi-leaf spring rear suspension. At 6.5" of rear lift - achieved through aftermarket leaf spring packs, add-a-leaf systems, blocks, or a combination - shock mounting geometry, effective spring rate, and suspension travel differ substantially from stock. The 987-24-025 is valved specifically for the rear suspension behavior of this generation at 6.5" of lift, accounting for the altered shock angle, spring rate, and motion ratios that result.
• HTO (Hydraulic Top Out) is especially relevant at 6.5" of rear lift on a heavy-duty truck. The increased rear droop travel at extreme lift heights amplifies top-out events during off-road use, trailer coupling/uncoupling, and aggressive terrain. HTO's progressive hydraulic resistance at the end of extension travel reduces the harshness of these events, protecting U-bolts, axle housing mounts, and the shock's end stops from repeated mechanical impact.
• At 6.5" of rear lift, extended brake lines, driveshaft modifications, and potentially a track bar or panhard bar relocation may be required in addition to replacement shocks. Verify all complementary suspension hardware for your build before installation.
• This is a single shock - one unit per order. Two are required for a complete rear axle replacement.
• Installation is a direct bolt-on replacement for the factory rear shock - no drilling or modification to shock mounting points is required for the shock itself.

Features

• 2.5" body diameter - the 987-series 2.5" body provides substantially more oil volume than a 2.0" body shock, delivering greater heat capacity for sustained off-road use and more consistent damping under the demanding combined loading of heavy payload, towing, and lifted off-road operation that the Silverado/Sierra HD rear suspension regularly encounters. The larger body also accommodates a bigger main piston with more refined valving shim stacks for precise force curves across the full range of shock velocities.
• 6061-T6 aluminum body, Type II anodized - efficient heat dissipation vs. steel-bodied shocks, corrosion resistance, and durable surface protection in the harsh underbody environment of a work truck.
• Internal Floating Piston (IFP) - physically separates shock oil from the high-pressure nitrogen gas charge to prevent aeration. At 6.5" of lift, the altered suspension geometry and increased travel intensity of the GM HD rear suspension make IFP-based consistent damping more important than at stock ride height - where a non-IFP shock can begin to fade under repeated aggressive cycling.
• Hydraulic Top Out (HTO) - as the shock approaches full extension, the HTO piston routes oil through a secondary shim stack that provides progressive hydraulic resistance, decelerating the shaft before mechanical contact. At 6.5" of rear lift, the GM HD's increased rear droop makes top-out events more frequent and forceful during off-road use. HTO converts these from abrupt impacts into controlled decelerations, improving ride quality and reducing stress on leaf spring hardware and axle components.
• Vehicle and lift-specific valving - the 987-24-025 is calibrated for the 2020-2025 Silverado/Sierra 2500/3500 HD rear suspension spring rates, axle weight, and geometry at 6.5" of lift. The valving accounts for both the loaded (payload/towing) and unloaded conditions the GM HD rear suspension encounters in real-world use.
• 5/8" hard chrome shaft - resists bending under lateral loads generated by the altered geometry of a 6.5" lifted solid rear axle, with hard chrome surface treatment for long-term seal interface wear resistance.
• Bolt-on direct fit - installs to the factory rear shock mounting hardware on the 2020-2025 Silverado/Sierra 2500/3500 HD without modification to shock mounting points.

Specifications

• Part Number: 987-24-025
• Series: FOX Performance Series 2.5
• Type: Smooth Body IFP HTO Shock
• Position: Rear
• Vehicle Fitment: 2020-2025 Chevrolet Silverado 2500/3500 HD; 2020-2025 GMC Sierra 2500/3500 HD (4WD)
• Lift Range: 6.5"
• Body Diameter: 2.5"
• Body Material: 6061-T6 aluminum, Type II anodized, impact extruded
• Shaft: 5/8" hard chrome
• Reservoir Type: Internal Floating Piston (IFP) - smooth body, no external reservoir
• HTO (Hydraulic Top Out): Yes
• Valving: Vehicle/lift-specific; position-sensitive
• Installation: Bolt-on direct fit
• Quantity: 1 shock per order
• Warranty: 1-year limited warranty

Included Components

• 1x FOX 987-24-025 Performance Series 2.5 Smooth Body IFP HTO Rear Shock

Product Description

The FOX 987-24-025 is the Performance Series 2.5 Smooth Body IFP HTO rear shock for the 2020-2025 Chevrolet Silverado 2500/3500 HD and GMC Sierra 2500/3500 HD 4WD at 6.5" of rear lift - the highest lift range in the FOX 987-series rear shock lineup for the current-generation GM HD platform. It is the direct rear companion to the 987-24-024 front shock, completing the full-vehicle 6.5" lift shock package for this generation of GM HD trucks.

At 6.5" of rear lift, the Silverado/Sierra HD's solid rear axle and multi-leaf spring suspension operate with meaningfully different geometry, travel, and spring rates than a stock or moderately lifted truck. A shock valved for a lesser lift range would produce incorrect damping force at this geometry - too stiff or too soft in the wrong parts of the stroke - making lift-range-specific valving essential rather than optional. The 987-24-025's calibration accounts for the spring rates, motion ratios, and axle weight distribution specific to the 2020+ GM HD platform at 6.5" of elevation, and for the dual-use reality of HD trucks: payload and towing loads are part of the suspension's everyday workload, not exceptional conditions. The 2.5" body's oil volume handles these sustained, high-load conditions without fade, and the IFP maintains consistent gas/oil separation across repeated cycling. HTO's secondary shim stack provides progressive hydraulic resistance at full extension - converting increased-travel top-out events from mechanical impacts into controlled, cushioned decelerations.

The 987-24-025 is sold as a single unit; two are required for a complete rear replacement. Companion front shock: 987-24-024. At 6.5" of lift, extended brake lines, driveshaft modifications, and other lift-specific hardware must be confirmed as part of a complete build. FOX backs this shock with a 1-year limited warranty.