This technical manual details the service and repair procedures for AxleTech International HDL Single Reduction Differential Lock Carriers. These carriers utilize a Helical Gear Differential Lock (HDL), a hydraulic shift assembly that locks the axle shafts and differential assembly together for maximum traction in poor conditions.

1. Core Component Specifications

Proper assembly and maintenance rely on strict technical parameters:

Pinion Bearing Preload: Controlled via spacers. New bearings require a preload of 15–25 lb-in (1.7–2.8 N·m), while used bearings in good condition should be set to 5–25 lb-in (1.7–2.8 N·m).
Main Differential Bearing Preload: The standard specification is 15–35 lb-in (1.7–3.9 N·m). This can also be measured by bearing cap expansion: 0.002–0.009-inch for RS-160 models and 0.006–0.013-inch for RS-180 models.
Ring Gear Backlash: For gears with a pitch diameter of 17 inches or larger, the setting range is 0.010–0.020-inch, with a nominal setting of 0.015-inch for new gear sets.
Gear Runout: Maximum allowable ring gear runout is 0.008-inch (0.20 mm).

2. Critical Assembly Procedures

Matched Sets: Drive pinions and ring gears are matched sets and must always be replaced together.
Ring Gear Installation: Ring gears must be heated in water to 160°F–180°F (71°C–82°C) for 10 to 15 minutes before being installed on the case half. They should never be pressed on cold, as this can damage the case.
Pinion Depth Adjustment: Depth is controlled by shims between the bearing cage and carrier. Technicians must calculate new shim thickness based on previous measurements adjusted by Pinion Cone (PC) variation numbers die-cut on the gears.

3. Lubrication and Maintenance

Oil Standards: Use API GL-5 hypoid gear oil. Viscosity (e.g., 80W/90 or 75W/140) must be selected based on the minimum outside operating temperature.
Temperature Limits: Sump temperature must never exceed 250°F (121°C).
Change Intervals: Standard petroleum-based oil changes are required annually or every 25,000 miles for linehaul vocations, while synthetic intervals can reach 250,000 miles or 3 years.

4. Safety and Towing

Carrier Removal: Before removal or installation, the differential lock must be shifted into the locked (engaged) position using a manual engaging capscrew to provide necessary clearance from the axle housing.
Towing Requirements: Axle shafts must be removed before towing the vehicle with the drive wheels on the ground to prevent component damage.