HARNESS AS-ALARM 4715150 - Caterpillar

Introduction
Some Off-Highway Trucks may develop cracks in the 9D7899 axle housing. Cracking occurs at the casting bottom where the carrier assembly is assembled to the axle housing.This Special Instruction provides the necessary information for repairing the 9D7899 axle housing for Off-Highway Trucks. The guideline is published to enable dealers to make successful repairs with the benefit of cost reduction for customers. Successful axle housing repair depends on the extent of required repair, repair methods and repair quality. Illustrations in this publication may look different from your machine. While the illustrations are typical, the dimensions are actual. ALL DIMENSIONS LISTED ARE DIMENSIONS FOR MANUFACTURING AND ASSEMBLING A NEW MACHINE.Do not perform any procedure, outlined in this publication, or order any parts until you read and understand the information contained within.Reference: Service Manual and Parts BookInspection
The axle housing must be inspected prior to any weld repair. Crack inspection is necessary to prevent any failure following salvage.Although, cracking has occurred at the bottom of the housing/carrier assembly interface, the entire housing face area should be inspected to ensure no other cracks are present.
9D7899 Axle Housing. (A) Crack Location.The illustration above indicates the area for inspection. Inspection methods include dye penetrant or magnetic particle.In each inspection method, it may be necessary to prepare the surface with removal of any surface irregularities. Surface irregularities might mask the indications of unacceptable defects.Preparation
(B) Axle Housing Repaired Area-60° Double V-Groove Weld.1. Remove all oil, grease, paint, dirt and inspection media from the area. Remove surface oxides from the area that is to be repaired. Good cleaning and surface preparation is important, if a good quality repair is to be made.2. The crack may be removed using air carbon arc cutting. Remove 60 percent (depth) of crack using air carbon arc cutting, creating a U-groove.3. Use a rotary file to "dress" the sides and bottom of the weld joint to eliminate any carbon, rough edges and provide for a 60° opening.4. Visually inspect the prepared area to ensure the crack has been completely removed.Preheat/Postheat
1. Repairs should be made with the axle housing at a temperature of 20°C (68°F) with protection from drafts, especially in cold weather.2. Preheat the area to 149°C (300°F) to eliminate the hydrogen gas potential and to reduce stress.Maintain a 95°C (200°F) interpass weld temperature.3. Following the repair, postheat the weld area to 149°C (300°F) and allow the casting to slowly cool to room temperature.
Protect yourself and others; read and understand this warning. Fumes and gases can be dangerous to your health. Ultraviolent rays from the weld arc can injure eyes and burn skin. Electric shock can kill.Read and understand the manufacturer's instructions and your employer's safety practices. Keep your head out of the fumes. Use enough ventilation, exhaust at the arc, or both, to keep fumes and gasses from your breathing zone and the general area. Wear correct eye, ear and body protection. Do not touch live electrical parts.See American National Standard Z49.1, "Safety in Welding and Cutting" published by the American Welding