M85046 Shock Absorber

The M85046 is a heavy-duty twin-tube hydraulic shock absorber designed and manufactured by Meritor (formerly Rockwell Automation) for rear suspension applications in Class 8 commercial trucks, trailers, and heavy-duty vehicles. Engineered to withstand severe load conditions and rough road surfaces, this shock absorber delivers consistent damping performance, controls chassis vibration, and enhances overall ride comfort and stability for long-haul and vocational vehicles.

Built as part of the Meritor AllFit product line, the M85046 features a robust, one-piece steel construction with a large-bore hydraulic chamber and an integrated hydraulic stop that provides additional protection during extreme compression events. Its twin-tube design separates the working piston from the outer reservoir tube, improving heat dissipation and ensuring stable performance under continuous heavy use. The unit is factory-filled with high-viscosity hydraulic fluid formulated to resist foaming and maintain consistent damping characteristics across a wide temperature range.

Key physical and dimensional specifications include a 41 mm (1.63 in) bore diameter, a 55.5 mm (2.19 in) body diameter, and a 63.5 mm (2.5 in) dust shield diameter. The extended length measures 698.9 mm (27.52 in), the collapsed length is 421.8 mm (16.61 in), and the usable stroke is 277.1 mm (10.91 in). These dimensions make it suitable for a wide range of heavy-duty suspension configurations while ensuring compatibility with OEM mounting points.

The M85046 is equipped with heavy-duty end fittings designed for direct bolt-on installation. Both upper and lower mounts feature reinforced rubber bushings that isolate noise and vibration, reducing stress on the suspension frame and extending service life. The outer body is coated with a durable black paint finish that resists corrosion, rust, and abrasion in harsh operating environments, including exposure to road salt, moisture, and debris.

Performance characteristics include a compression force rating of 219 lbs and a rebound force rating of 1,019 lbs, providing balanced damping that controls both rapid compression and extension movements. The integrated hydraulic stop prevents metal-to-metal contact during full compression, protecting the shock absorber and suspension components from damage. This design also minimizes internal wear, ensuring long-term reliability and reducing maintenance requirements.

Cross-reference part numbers for the M85046 include Volvo 3947711, 3919958, 65415, 8026658, 89434, ATMA85046, ATMA89434, MERM89434, and MIDSA65415, making it a versatile replacement option for various OEM and aftermarket suspension systems. The unit carries a UPC code of 43645703738 and is classified under VMRS code 016-003-016 for standardized parts identification.

Ideal applications include rear suspension setups on heavy-duty trucks, semi-trailers, dump trucks, concrete mixers, and other vocational vehicles operating in demanding conditions. Whether for original equipment installation or fleet maintenance and replacement, the M85046 offers OEM-quality performance, durability, and value, backed by Meritor’s reputation for reliability in commercial vehicle components.