Meritor Trailer Suspension MPA405175 Parts List: A Complete Guide

The Meritor MPA405175 is a popular trailer air ride suspension model used on many heavy-duty trailers. Whether you are maintaining a fleet or replacing worn components, having a reliable parts list is essential. This guide provides a practical breakdown of the key parts for the MPA405175, along with tips for identifying the correct components and ensuring proper fitment.

Understanding the Meritor MPA405175 Suspension

The MPA405175 is part of Meritor's heavy-duty trailer air ride series, designed for capacities around 20,000 to 25,000 pounds per axle. It features a trailing arm design with air springs and shock absorbers. The “MPA” stands for Meritor Parallelogram Air, and the numbers indicate specific dimensions and load ratings. Before ordering parts, confirm your suspension’s model number (usually stamped on the axle or side of the hanger) and the axle capacity.

Complete Parts List for MPA405175

Below is a comprehensive list of commonly replaced components. Always verify with your suspension’s serial number or contact a Meritor dealer to ensure compatibility.

1. Air Springs (Air Bags)

• Part Numbers: Commonly use Meritor #RK1050 or equivalent (often Firestone 1T15M-2).
• Description: Two air springs per axle, mounted between the trailing arm and frame bracket.
• Tip: Check the air spring height when unloaded – typically 6.5-7.5 inches. Replace in pairs.

2. Shock Absorbers

• Part Numbers: Meritor #RKH1153 or Gabriel 83002.
• Description: Twin shocks per axle, mounted on the trailing arm and frame.
• Tip: Always replace shocks in pairs and consider upgrading to heavy-duty units for improved damping.

3. Bushings – Control Arm and Hanger

• Control Arm Bushings: Meritor #RKH1351 (front) and #RKH1352 (rear).
• Hanger Bushings: Meritor #RKH1353.
• Description: Polyurethane or rubber bushings press into the control arm eyes and hanger points. Worn bushings cause loose steering and uneven tire wear.
• Tip: Use a bushing press tool to avoid damage. Lubricate with silicone grease.

4. Height Control Valve (Leveling Valve)

• Part Number: Meritor #RKH1380 or Haldex 90501423.
• Description: Maintains ride height by controlling air flow to the air springs.
• Tip: Adjust the valve arm to the correct ride height (typically 6-8 inches from axle pad to frame).

5. Air Lines and Fittings

• Air Lines: Use 3/8-inch DOT air brake line (nylon or copper).
• Fittings: Meritor #RKH1395 (elbow) and #RKH1396 (straight).
• Tip: Replace any cracked or chafed air lines. Use compression fittings for quick repair.

6. Torque Rods (Optional)

• Part Number: Meritor #RKH1400 (longitudinal) and #RKH1401 (transverse).
• Description: Not always present on MPA405175, but some setups include torque rods for axle alignment.
• Tip: If your suspension has them, replace the bushings at each end separately.

7. Hardware Kits

• Part Number: Meritor #RKH1420 (connection hardware for control arms and hangers).
• Description: Includes bolts, lock nuts, and washers. Use grade 8 hardware.
• Tip: Always replace fasteners when installing new bushings to prevent loosening.

8. Axle Alignment Shims

• Part Number: Meritor #RKH1430 (0.5-degree) and #RKH1431 (1-degree).
• Description: Used to correct toe and camber after bushing replacement.
• Tip: Have your axle alignment checked at a qualified shop after any suspension work.

How to Identify the Correct Parts

1. Locate the Model Number: Look on the side of the hanger bracket or near the axle beam. It should read “MPA405175” or similar.
2. Check the Axle Capacity: Usually stamped on the axle tube. Common ratings are 20,000 lb, 22,500 lb, or 25,000 lb.
3. Measure Key Dimensions: Air spring mounting centers, control arm length (approx. 26 inches for MPA405175), and ride height.
4. Use a Cross-Reference: Many aftermarket brands (like Reyco Granning or Hendrickson) have compatible parts. Ask your supplier for a cross-reference for Meritor MPA405175.

Ordering Tips and Compatibility

• Original Equipment vs. Aftermarket: OEM Meritor parts guarantee fit, but aftermarket options (e.g., Firestone air springs, Gabriel shocks) are often interchangeable and may cost less.
• Purchase Complete Kits: Some suppliers offer rebuild kits that include all bushings, air springs, and shocks for one axle. This saves time and ensures compatibility.
• Check for Updates: Meritor occasionally updates part numbers. For example, the current shock absorber may be a different number than the original. Always confirm with your supplier.
• Avoid Used Parts: Suspension wear items have limited life. New parts are safer and more reliable.

Final Recommendation

For routine maintenance of your Meritor MPA405175 suspension, start by inspecting the air springs and bushings – these wear fastest. Replace all rubber components in pairs or axles sets. Use a quality rebuild kit (e.g., Meritor RKH1450 for control arm bushings and hardware) to ensure consistent performance. Always torque fasteners to specification (typically 300-400 ft-lbs for control arm bolts). If you are unsure about part numbers, provide your trailer VIN and suspension model to a trusted heavy-duty parts supplier – they can look up the exact components for your application. Proper maintenance of the MPA405175 will extend suspension life, improve ride quality, and reduce downtime.