Timbren 2011-2023 GMC/Chevy 2500/3500 Custom Specs for GMRCK25D

Maximize Load Control on Your 2011-2023 Silverado or Sierra HD with the Timbren GMRCK25DM1.5 and the 1.5-Inch Spacer

The Timbren GMRCK25DM1.5 is a rear suspension enhancement system (SES) bump stop upgrade for the 2011-2023 Chevrolet Silverado 2500HD, Silverado 3500HD, GMC Sierra 2500HD, and Sierra 3500HD in both 2WD and 4WD configurations.

It replaces the factory rear jounce stop on the frame with a progressive hollow rubber spring that engages as load is applied, automatically compensating for payload and trailer tongue weight to keep the rear end level and in control.

The GMRCK25DM1.5 includes a 1.5-inch custom spacer, providing additional height compared to the 1-inch M1 spacer, for applications where the factory or installed suspension geometry results in a larger unloaded gap between the bump stop mounting surface and the axle. Rated at 8,600 lbs capacity and manufactured in Canada by Timbren, this is a direct bolt-on replacement for the factory jounce stops with no welding, cutting, or suspension disassembly required.

Key Features

• Replaces factory jounce stops with progressive hollow rubber springs for supplemental rear load support
• Prevents rear sag under heavy payloads and trailer tongue weight
• Progressive spring rate engages automatically as load increases for a self-leveling effect
• Includes 1.5-inch custom spacer for larger unloaded gap applications
• Rated at 8,600 lbs capacity
• Fits 2011-2023 Chevy Silverado and GMC Sierra 2500HD and 3500HD in 2WD and 4WD
• Direct bolt-on installation with no cutting, welding, or suspension modification required
• Made in Canada by Timbren Industries

Vehicle Fitment

Specifications

What's Included

• 2x Timbren hollow rubber progressive rate spring bump stops (left and right)
• 1.5-inch custom spacers
• Hardware for installation

About Timbren

Timbren Industries is a Canadian manufacturer of suspension enhancement systems trusted by truck and commercial vehicle operators across North America for reliable, maintenance-free load control. The Timbren SES product line covers a wide range of light truck, van, and SUV platforms with direct bolt-on fitment, replacing factory bump stops with progressive hollow rubber springs that provide an automatic load-leveling effect without the complexity of air suspension systems.

Related Parts on Our Site

• Timbren GMRCK25DM1 2011-2023 Chevy GMC 2500 3500 Rear Bump Stop 1-Inch Spacer - Same kit with a 1-inch spacer for standard gap applications

Frequently Asked Questions

What is the Timbren GMRCK25DM1.5?

The Timbren GMRCK25DM1.5 is a rear suspension enhancement system for the 2011-2023 Chevrolet Silverado and GMC Sierra 2500HD and 3500HD. It replaces factory jounce stops with progressive hollow rubber springs to eliminate rear sag under load. The 1.5 suffix indicates the kit includes a 1.5-inch custom spacer for applications needing greater height adjustment compared to the standard 1-inch M1 spacer.

How do I know whether to order the M1 or M1.5 spacer?

Timbren recommends measuring the gap between the bump stop mounting surface on the frame and the top of the rear axle with the truck at stock ride height and unloaded. If the gap is larger and the 1-inch M1 spacer would not bring the rubber spring close enough to achieve the required half-inch to one-and-a-half-inch unloaded gap, the 1.5-inch M1.5 spacer is the correct choice. Trucks with leveling kits, slightly higher-than-stock ride heights, or worn factory suspension may have a larger gap that the M1.5 addresses.

Does the Timbren GMRCK25DM1.5 increase the truck's GVWR?

No. Installing the Timbren SES does not change the Gross Vehicle Weight Rating of the vehicle. The GVWR is set by the manufacturer and cannot be increased by suspension upgrades. The Timbren system improves load control and prevents sag but does not authorize loading the vehicle beyond its rated GVWR.

Will the 1.5-inch spacer affect unloaded ride quality?

The Timbren spring is designed with a gap between the rubber spring and the axle when the truck is empty. When correctly installed, the spring does not contact the axle under light driving loads, so unloaded ride quality is not significantly impacted. The additional 0.5 inch of the M1.5 spacer versus the M1 adjusts the gap height, not the spring rate itself. If the spacer results in the spring contacting the axle under no load, the spacer selection should be reconsidered.

Is the GMRCK25DM1.5 compatible with 2WD and 4WD trucks?

Yes. The Timbren GMRCK25DM1.5 fits both 2WD and 4WD configurations of the 2011-2023 Chevrolet Silverado 2500HD, Silverado 3500HD, GMC Sierra 2500HD, and Sierra 3500HD, including Cab and Chassis variants.

Does this kit work with trucks that have aftermarket suspension or lift kits?

Possibly, but Timbren recommends verifying the unloaded gap between the bump stop mount and the axle after any lift kit installation before ordering. Lift kits can change this gap, and the correct spacer selection depends on the actual gap in your specific installation. The M1.5 spacer is often the better choice for trucks with leveling kits or mild lifts that open up the gap slightly compared to stock height.

Does the GMRCK25DM1.5 require any drilling or welding?

No. The GMRCK25DM1.5 is a direct bolt-on replacement for the factory rear jounce stops on the frame. No drilling, welding, or cutting of any vehicle component is required. Standard hand tools are sufficient for installation.

How does the Timbren SES compare to airbag kits for the 2500HD and 3500HD?

Air bag kits for the 2500HD and 3500HD add an adjustable air spring inside the coil or alongside the leaf spring, requiring an air compressor or on-board air system to adjust pressure as load changes. Timbren SES requires no compressor, no air lines, and no maintenance. The Timbren rubber spring adjusts automatically and progressively as load increases, without any driver input. Air bag systems offer on-demand adjustability that Timbren does not, but for operators who want a set-and-forget solution for consistent hauling loads, Timbren is simpler and more reliable long-term.

Installation Instructions

1. Safely lift the rear of the vehicle and support it on jack stands. Verify the rear axle is supported and the vehicle is stable.
2. Locate the factory jounce stop on the frame rail above each side of the rear axle.
3. Remove the factory jounce stop by unbolting it from the frame bracket.
4. With the suspension at ride height, measure the gap between the bump stop mounting surface and the axle pad to confirm the 1.5-inch spacer is the correct selection. Target is a half-inch to one-and-a-half-inch gap after the Timbren spring is installed.
5. Attach the 1.5-inch spacer to the Timbren mount bracket as directed by the included instructions.
6. Position the GMRCK25DM1.5 onto the frame bracket and install with the provided hardware.
7. Torque fasteners to the specification in the Timbren installation instructions.
8. Repeat on the opposite side.
9. Lower the vehicle and verify the unloaded gap is within spec on both sides.
10. Test-drive the truck loaded to a typical working load to confirm rear sag is controlled.