Radflo 2.5 Rear Shock – Toyota FJ Cruiser / 4Runner / Lexus GX – 6" Rough Country Lift | 6ST-001-20

Upgrade the rear suspension of your lifted Toyota or Lexus with the Radflo 2.5-Inch Rear IFP Shock, part #6ST-001-20, specifically designed for vehicles equipped with a 6-inch Rough Country suspension lift.

This extended-length rear shock provides a premium replacement or performance upgrade for compatible Toyota FJ Cruiser, Toyota 4Runner and Lexus GX applications using the 6-inch Rough Country suspension system.

The Radflo 6ST-001-20 features a large 2.5-inch shock body, Internal Floating Piston (IFP) design, nitrogen-gas pressurization and velocity-sensitive deflective-disc valving for controlled and consistent damping both on the street and off-road.

Unlike a disposable replacement shock, Radflo shocks are rebuildable, serviceable and tunable, making the 6ST-001-20 an excellent long-term upgrade for vehicles that already have a 6-inch Rough Country lift installed.

IMPORTANT: Rear shocks are sold individually. Order quantity 2 to replace both rear shocks.

Vehicle Fitment

Designed for applicable vehicles equipped with a:

6-Inch Rough Country Suspension Lift

Toyota FJ Cruiser

• 2007-2014 FJ Cruiser

• 2007 TRD Special Edition

• 2008 Trail Teams Special Edition

Toyota 4Runner

• 2003-2024 4Runner

• Applicable SR5, SR5 Premium, Limited, Sport, Trail, TRD Off-Road, TRD Off-Road Premium, TRD Pro, TRD Sport, Venture, Nightshade and other listed trims

Lexus GX

• 2003-2009 GX470

• 2010-2023 GX460

• Applicable GX460 Premium, Luxury and Black Line models

Critical Fitment Note

This is NOT a standard-height or conventional 2-3 inch lift rear shock.

The 6ST-001-20 is specifically intended for applications using a 6-inch Rough Country suspension lift.

Customers with stock suspension or a conventional 2-3 inch suspension lift should select the appropriate Radflo rear shock for their suspension configuration.

Always verify the suspension system installed on the vehicle before ordering.

Key Features

• Genuine Radflo Suspension Technology

• Part number 6ST-001-20

• Designed for compatible 6-inch Rough Country lift systems

• Rear shock absorber

• 2.5-inch diameter shock body

• Internal Floating Piston (IFP) design

• Smooth-body shock

• Nitrogen-gas pressurized

• Radflo aluminum Freeflo piston

• Velocity-sensitive deflective-disc valving

• Self-adjusting damping

• SSID alloy-steel shock body

• CNC-machined 6061 aluminum components

• High-temperature foam-resistant Radflo suspension fluid

• Mirror-polished chrome-plated steel rod

• PTFE-coated CNC-machined bronze rod guide

• Rebuildable combination quad-ring and lip seal

• Consumer or factory tunable

• Consumer or factory serviceable

• OE-location mounting

• Designed for consistent on-road and off-road performance

• Made in the USA

• Sold individually

Designed for 6-Inch Rough Country Lift Systems

A 6-inch suspension lift changes the operating position and required travel range of the rear shocks compared with a stock-height or mildly lifted vehicle.

The Radflo 6ST-001-20 is specifically designed for the 6-inch Rough Country lift application, making it an excellent option when replacing worn rear shocks on an existing Rough Country-equipped FJ Cruiser, 4Runner or compatible Lexus GX.

2.5-Inch Shock Body

The Radflo 6ST-001-20 utilizes a large:

2.5-Inch Diameter Shock Body

The larger shock body provides increased oil volume compared with smaller conventional replacement shocks, helping maintain more consistent damping during demanding suspension use.

This makes the shock well suited for:

• Daily driving

• Highway driving

• Rough roads

• Washboard roads

• Trail use

• Overlanding

• Off-road driving

• Repeated suspension cycling

Internal Floating Piston (IFP)

The 6ST-001-20 uses an:

Internal Floating Piston (IFP)

The floating piston separates the shock oil from the pressurized nitrogen gas.

This design helps reduce fluid aeration and cavitation during repeated suspension cycling, allowing the shock to maintain more consistent damping as operating conditions become more demanding.

Nitrogen Gas Pressurized

The Radflo 6ST-001-20 is nitrogen-gas pressurized.

Nitrogen pressure helps maintain consistent suspension-fluid behavior and reduces the potential for aeration during rapid suspension cycling.

The result is predictable damping during both everyday driving and demanding off-road use.

Velocity-Sensitive Deflective-Disc Valving

The 6ST-001-20 uses Radflo's:

Velocity-Sensitive Deflective-Disc Valving

This allows the damping response to react to the speed of suspension movement.

The shock can therefore provide appropriate damping characteristics across different driving conditions, helping balance:

• Ride quality

• Body control

• Suspension stability

• Small-bump compliance

• Larger impacts

• Off-road suspension movement

Radflo classifies the shock's damping adjustment as self-adjusting.

Radflo Freeflo Piston

Inside the 6ST-001-20 is Radflo's:

Aluminum Freeflo Piston

The piston works with Radflo's velocity-sensitive valving to precisely control suspension-fluid movement through the shock.

This contributes to predictable damping and consistent suspension performance across varying road and trail conditions.

High-Temperature Suspension Fluid

Radflo fills the shock with:

High-Temp Foam-Resistant Suspension Fluid

Repeated suspension movement generates heat. Radflo's suspension fluid is designed to resist foaming and maintain consistent damping characteristics as operating temperatures increase.

This is particularly useful during extended off-road driving and repeated suspension cycling.

Premium Shock Construction

Radflo uses high-quality materials throughout the 6ST-001-20.

Shock Body: SSID alloy steel
Body Style: SSID alloy-steel tube
Body Cap: CNC-machined 6061 aluminum
Body Cap Finish: Anodized
Piston: Radflo aluminum Freeflo piston
Rod: Steel
Rod Finish: Mirror-polished chrome plating
Rod Guide: CNC-machined bronze with PTFE coating
Seal: Rebuildable combination quad-ring and lip seal

Rebuildable & Serviceable

Unlike many replacement shocks that are discarded when they wear out, Radflo designs the 6ST-001-20 to be serviceable and rebuildable.

Radflo lists the shock as:

Consumer or Factory Serviceable

The rebuildable construction allows worn seals, suspension fluid and other service components to be replaced rather than requiring replacement of the complete shock.

Tunable Valving

Radflo also lists the 6ST-001-20 as:

Consumer or Factory Tunable

The shock can therefore be tuned for specialized vehicle configurations and additional vehicle weight.

Custom tuning may be beneficial for vehicles equipped with:

• Heavy rear bumpers

• Swing-out tire carriers

• Oversized spare tires

• Roof racks

• Drawer systems

• Overland equipment

• Camping equipment

• Additional fuel or water

• Permanent cargo loads

OE-Location Mounting

Radflo specifies the 6ST-001-20 as mounting in the:

OE Location Using OE-Style Hardware

This allows the shock to integrate with the compatible 6-inch Rough Country suspension configuration without requiring custom-fabricated rear shock mounts.

Excellent Upgrade for an Existing 6-Inch Rough Country Lift

The 6ST-001-20 is particularly useful for owners who already have a 6-inch Rough Country suspension lift but need to replace worn or underperforming rear shocks.

Instead of replacing the complete suspension system, the Radflo 2.5-inch rear shocks provide a premium, serviceable damper option designed for the existing lifted suspension configuration.

The upgrade provides:

• Large 2.5-inch shock bodies

• IFP construction

• Application-specific configuration

• Premium internal components

• Rebuildable construction

• Serviceable design

• Tunable valving

• Nitrogen-gas pressurization

Matching Front Coilover Kit

For a complete Radflo suspension upgrade on compatible vehicles equipped with a 6-inch Rough Country lift, Radflo also offers:

Radflo 6CT-001-20 – 2.5-Inch Front Coilover Kit

The front kit is sold as a pair and includes complete Radflo coilovers with Eibach springs.

For a complete front and rear Radflo setup:

Front: 6CT-001-20 – Qty. 1 Kit
Rear: 6ST-001-20 – Qty. 2 Shocks

Sold Individually

IMPORTANT: Radflo sells the 6ST-001-20 individually.

One part number equals:

1 Rear Shock

For a complete rear shock replacement, order:

Quantity 2

What's Included

Each Radflo 6ST-001-20 includes:

• (1) Radflo 2.5-inch rear IFP shock

• Application-specific mounting configuration

Quantity 2 is required for a complete left and right rear shock replacement.

Product Specifications

Manufacturer: Radflo Suspension Technology
Part Number: 6ST-001-20
Series: 600R Pro
Product Type: Rear Shock Absorber
Application: 6-Inch Rough Country Lift
Position: Rear
Sold As: Each
Shock Diameter: 2.5 Inch
Shock Type: IFP
Shock Style: Smooth Body
Adjustment: Self-Adjusting
Valving: Velocity-Sensitive Deflective Disc
Piston: Radflo Aluminum Freeflo Piston
Body Material: SSID Alloy Steel
Body Style: SSID Alloy-Steel Tube
Body Cap Material: CNC-Machined 6061 Aluminum
Body Cap Finish: Anodized
Rod: Steel
Rod Finish: Mirror-Polished Chrome Plating
Rod Guide: CNC-Machined Bronze
Rod Guide Finish: PTFE Coating
Seal: Rebuildable Combination Quad Ring & Lip Seal
Shock Oil: Radflo High-Temp Foam-Resistant Suspension Fluid
Pressurization: Nitrogen Gas
Mounting: OE Location & Hardware
Tuning: Consumer or Factory Tunable
Service: Consumer or Factory Serviceable
Country of Origin: USA
Warranty: 1-Year Limited Warranty

Frequently Asked Questions

What is Radflo part #6ST-001-20?
The 6ST-001-20 is a 2.5-inch rear IFP shock designed for compatible Toyota FJ Cruiser, Toyota 4Runner and Lexus GX vehicles equipped with a 6-inch Rough Country suspension lift.

Does the 6ST-001-20 have a remote reservoir?
The product is shown and identified as a smooth-body IFP rear shock. Radflo's current online specification table contains a conflicting “Remote Reservoir” field, so we do not advertise this version as a remote-reservoir shock.

Are these shocks sold as a pair?
No. The 6ST-001-20 is sold individually. Order quantity 2 for a complete rear set.

Will it fit a 2007-2014 Toyota FJ Cruiser?
Radflo's current fitment data lists 2007-2014 Toyota FJ Cruiser applications. The vehicle must have the compatible 6-inch Rough Country lift.

Will it fit a Toyota 4Runner?
Radflo lists numerous 2003-2024 Toyota 4Runner applications. The critical requirement for this particular shock is the compatible 6-inch Rough Country suspension lift.

Will it fit a Lexus GX?
Radflo's current application data includes 2003-2009 Lexus GX470 and 2010-2023 Lexus GX460 applications.

Will this shock work on a stock-height vehicle?
No. This specific shock is intended for the 6-inch Rough Country lift application.

Will it work with a conventional 2-3 inch lift?
This is not the normal Radflo rear shock for a conventional 2-3 inch suspension lift. Select the appropriate Radflo shock for the actual suspension configuration.

Is this an IFP shock?
Yes. Radflo identifies the shock type as IFP, or Internal Floating Piston.

Is it rebuildable?
Yes. Radflo lists the shock as consumer or factory serviceable and uses a rebuildable sealing system.

Can the valving be changed?
Yes. Radflo lists the 6ST-001-20 as consumer or factory tunable.

What front coilovers match this rear shock?
For compatible vehicles using the 6-inch Rough Country lift, the matching front application is Radflo 6CT-001-20.

Where are Radflo shocks made?
Radflo lists the country of origin as USA.

What warranty is included?
Radflo lists a 1-Year Limited Warranty.