SPRING 9J1793 - Caterpillar

Introduction
This instruction provides the necessary information to reinforce the trailer main frames on the above machines.This reinforcement procedure is used to prevent or repair cracks. These cracks can occur in the welded joint between the rear diaphragm plate of the trailer front sub assembly and the inner arch plate of the frame.Do not perform any procedure, outlined in this publication, or order any parts until you read and understand the information contained within.Reference: Operation & Maintenance Manual (OMM), Service ManualRepair Procedure
Location of possible cracks.The cracks start in the vertical welds and, if left undetected, they can progress through the horizontal welds. The locations of these potential cracks are shown in the illustration above.
Right Hand Gusset.
Left Hand Gusset.1. Fabricate right hand gusset (1) and left hand gusset (2) to the dimensions in the illustrations above.
Reinforcement Plate.2. Fabricate two reinforcement plates (3) to the dimensions in the illustration above. Use structural steel with a minimum tensile strength of 490 MPa (71050 psi) and a minimum yield strength of 345 MPa (50025 psi) when fabricating the right and left Hand gussets and the reinforcing plates.
Connect the steering frame lock links or anti-articulation device between the front and rear frames before working on machine.
3. Lower the rear suspension, if equipped, to the service position. Refer to the OMM for the procedure to lower the suspension.4. Remove the rear drive shaft and four wheel drive actuating chamber to gain access to the area.5. Thoroughly clean the affected area and inspect for cracks.6. Vee out any cracks found and weld them. Use AWS E7018 electrodes or equivalent for all welds.
Weld Detail.
To prevent possible damage, provide protection for any brake hoses and the oscillating hitch seal before welding.
7. Tack weld the right hand gusset (1) and the left hand gusset (2) in position as shown in the above illustration.8. Tack weld the two reinforcement plates (3) in the position shown in the illustration above.9. When all four items are correctly positioned, fully weld as shown in the illustration above. Ensure that full size welds are provided.10. Ensure that the new welds do not undercut the existing bottom plate (D). As the thickness of the reinforcement plates reduce below 12 mm (0.5") (due to taper), reduce the size of the weld fillet accordingly.11. Make a 12 mm (0.5") fillet weld location (A) on the left and right gussets.* DO NOT weld in the arch plate radius (B).12. Make a 10 mm (0.39") fillet weld (C) around the "nose" of the plates.13. Clean the repaired areas and paint.14. Install the four wheel drive actuating chamber and the rear drive shaft.15. Remove the steering frame lock links or the anti-articulation device.