6 hours ago
The RD-20-145 and Its Engineering Lineage
The RD-20-145 rear axle is part of a family of tandem drive axles developed for high-load vocational trucks, especially in construction, logging, and oilfield service. Manufactured under the Meritor brand, which evolved from Rockwell’s heavy-duty drivetrain division, the RD-20-145 was designed to deliver durability, torque capacity, and long service life under punishing conditions.
This axle series shares design principles with the earlier SSHD (Single Speed Heavy Duty) axles, known for their robust carrier housings and gear sets. The RD-20-145 incorporates a 145-series carrier, which features a larger ring gear and thicker housing walls compared to lighter-duty models. These design elements contribute to higher Gross Combination Weight (GCW) ratings and improved thermal dissipation during extended hauling.
Core Specifications and Functional Highlights
Key attributes of the RD-20-145 include:
Operators and fleet managers have reported strong performance from RD-20-145 axles in demanding environments. In one example from a hauling company in Alberta, trucks equipped with RD-20-145 rears consistently exceeded 900,000 miles without major failures. The axles handled steep grades, heavy payloads, and seasonal temperature swings with minimal downtime.
Compared to Eaton 404s, which are also widely used in vocational fleets, the RD-20-145 offers superior durability in off-road and mixed-terrain conditions. The thicker carrier housing and larger gear set reduce the risk of gear tooth fatigue and bearing failure under shock loads.
Common Maintenance Considerations
While the RD-20-145 is known for its longevity, proper maintenance is essential:
Upgrade and Retrofit Potential
For older trucks or rebuilds, RD-20-145 axles can be retrofitted with:
Field Story from a Logging Operation
In 2011, a logging contractor in Oregon replaced Eaton 404 axles with RD-20-145 units on three Kenworth T800s. The terrain included steep switchbacks and muddy access roads. Over five years, the RD-20-145 axles required only routine fluid changes and one seal replacement. The contractor noted improved traction and reduced driveline vibration, attributing it to the axle’s heavier carrier and better gear engagement.
Recommendations for Fleet Managers
The RD-20-145 rear axle stands out as a reliable, heavy-duty solution for tandem drive applications. Its design roots in Rockwell’s SSHD lineage, combined with modern enhancements, make it a preferred choice for fleets operating in rugged conditions. With proper maintenance and thoughtful integration, these axles can deliver exceptional service life and performance across a wide range of industries.
The RD-20-145 rear axle is part of a family of tandem drive axles developed for high-load vocational trucks, especially in construction, logging, and oilfield service. Manufactured under the Meritor brand, which evolved from Rockwell’s heavy-duty drivetrain division, the RD-20-145 was designed to deliver durability, torque capacity, and long service life under punishing conditions.
This axle series shares design principles with the earlier SSHD (Single Speed Heavy Duty) axles, known for their robust carrier housings and gear sets. The RD-20-145 incorporates a 145-series carrier, which features a larger ring gear and thicker housing walls compared to lighter-duty models. These design elements contribute to higher Gross Combination Weight (GCW) ratings and improved thermal dissipation during extended hauling.
Core Specifications and Functional Highlights
Key attributes of the RD-20-145 include:
- Tandem axle configuration with equal load distribution
- 46-spline axle shafts for increased torque transfer
- Carrier options with differential lock and inter-axle differential (IAD)
- Compatibility with Cam-Master® brake systems and RSA wedge brakes
- Available gear ratios ranging from 3.55 to 6.14 depending on application
- Carrier: The central gear housing that contains the differential and ring gear.
- IAD (Inter-Axle Differential): A mechanism that allows speed differentiation between front and rear axles in a tandem set.
- Diff lock: A feature that locks the differential to prevent wheel slip in low-traction conditions.
Operators and fleet managers have reported strong performance from RD-20-145 axles in demanding environments. In one example from a hauling company in Alberta, trucks equipped with RD-20-145 rears consistently exceeded 900,000 miles without major failures. The axles handled steep grades, heavy payloads, and seasonal temperature swings with minimal downtime.
Compared to Eaton 404s, which are also widely used in vocational fleets, the RD-20-145 offers superior durability in off-road and mixed-terrain conditions. The thicker carrier housing and larger gear set reduce the risk of gear tooth fatigue and bearing failure under shock loads.
Common Maintenance Considerations
While the RD-20-145 is known for its longevity, proper maintenance is essential:
- Use synthetic gear oil with high thermal stability and anti-wear additives
- Replace axle seals and inspect bearings every 250,000 miles
- Monitor carrier temperature during extended hauls
- Check diff lock engagement and air line integrity quarterly
- Inspect yokes and flanges for wear and torque loss
Upgrade and Retrofit Potential
For older trucks or rebuilds, RD-20-145 axles can be retrofitted with:
- Aluminum carrier housings for weight reduction
- Bolt-on diff locks for enhanced traction control
- Integrated oil pumps for improved lubrication
- Magnetic drain plugs to capture metal debris
- High-ratio gear sets for fuel economy optimization in highway applications
Field Story from a Logging Operation
In 2011, a logging contractor in Oregon replaced Eaton 404 axles with RD-20-145 units on three Kenworth T800s. The terrain included steep switchbacks and muddy access roads. Over five years, the RD-20-145 axles required only routine fluid changes and one seal replacement. The contractor noted improved traction and reduced driveline vibration, attributing it to the axle’s heavier carrier and better gear engagement.
Recommendations for Fleet Managers
- Match axle ratio to engine torque curve and terrain profile
- Train drivers on proper diff lock usage to avoid premature wear
- Maintain detailed service logs for each axle set
- Collaborate with Meritor-certified shops for rebuilds and part sourcing
- Use OEM parts for carrier rebuilds to preserve gear mesh integrity
The RD-20-145 rear axle stands out as a reliable, heavy-duty solution for tandem drive applications. Its design roots in Rockwell’s SSHD lineage, combined with modern enhancements, make it a preferred choice for fleets operating in rugged conditions. With proper maintenance and thoughtful integration, these axles can deliver exceptional service life and performance across a wide range of industries.
