Usage:
120H (6TM, 4MK, 6NM, 5FM, 9YR, 2AN, 9FN, 3GR),
135H (3YK, 7MM, 8WN) Motor Graders
Reference: Service Manual, SENR8540; Disassembly & Assembly, 120H, 135H Motor Graders.
Description of Change: A baffle plate has been added inside the motor grader case and frame to prevent oil from splashing onto the transmission dipstick. This splashing has caused inaccurate oil level readings in the past.
Adaptable To: The change to the 8W-5880 Case and Frame Assembly and the 112-4744 Case and Frame Assembly is effective with 120H (6TM374, 4MK440, 6NM250, 5FM800, 9YR330, 2AN104, 9FN471, 3GR70) and 135H (3YK277, 7MM249, 8WN350) Motor Graders, and is adaptable to earlier machines by using the following procedure.
Weld Information
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Protect yourself and others; read and understand this warning. Fumes and gases can be dangerous to your health. Ultraviolet rays from the weld arc can injure eyes and burn skin. Electric shock can kill.
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Read and understand the manufacturer's instructions and your employer's safety practices. Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and 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 Society, 2501 N.W. 7th Street, Miami, Florida 33125: OSHA Safety and Health Standards, 29 CRF 1910, available from U.S. Dept. of Labor, Washington, D.C. 20408.
NOTE: Welding operator personal protection should be provided to assure that total weld fume in the operators breathing zone does not exceed OSHA limits.
All repair welding operators must be qualified for groove and fillet welding as outlined in the current ANSI/AWS D14.3. The qualification will be for the SMAW (Shielded Metal Arc Welding) process in the vertical welding positions. The welding operator must also have used this welding process during the last six months or be re-certified for this process before welding. Documentation must be maintained of the weld operators qualifications. The alternate process for this repair could be FCAW (Flux Cored Arc Welding).
The area to be welded and the surrounding area must be at a minimum temperature of 16° C (60° F) before and during welding.
NOTE: Since weld distortion is a possibility, minimizing the heat is important.
The SMAW process shall be used with E7018 (ANSI/AWS A5.5) welding electrode. The weld deposited by these electrodes will have the following minimum mechanical properties:
- 500 MPa (72 KSI) Tensile Strength
- 420 MPa (60 KSI) Yield Strength
- 22% elongation in 50 mm (2 in)
- 27 J (20 ft lb) Notch Toughness at -29° C (20° F)
- 420 MPa (60 KSI) Yield Strength
These are low hydrogen electrodes and must be stored in an electrode oven at 121° C (250° F) when not in use. If the electrodes get damp, scrap or recondition them to the manufacturer's specifications.
The following chart relates to the electrodes diameter and approximate current settings for welding:
Use the direct current electrode positive (DC reverse polarity) polarity setting and remove the slag after every pass. The weld pass size shall not exceed two times the electrode diameter.
As an alternate process the FCAW process may be used with E71T-1 (ANSI/A5.20) welding electrode and the manufacturer's specified shielding gas(es). The weld deposited by three electrodes will have the following minimum mechanical properties:
- 500 MPa (72 KSI) Tensile Strength
- 420 MPa (60 KSI) Yield Strength
- 22% elongation in 50 mm (2 in)
- 27 J (20 lb ft) Notch Toughness at -18° C (0° F)
- 420 MPa (60 KSI) Yield Strength
NOTE: This type of electrode has limitations if it is used to carry larger weld pass volumes in the flat welding position. Due to the fast freezing characteristics of this electrodes slag system, there is a chance of trapping evolving gases in the weld melt. Precaution should be taken by controlling weld pass size.
Welding parameters will vary due to weld position and manufacturer of the welding electrode. For 1.30 mm (.052 in) diameter electrode typical welding parameters should be:
Use the direct current electrode positive (DC reverse polarity) polarity setting and remove the slag after every pass. The weld pass size shall not exceed 8.0 mm (.31 in) fillet volume.
Clean the metal of oil, grease, paint, and dirt in the area to be welded. Attach the welding ground cable directly to the area to be welded. Protect all machined surfaces from sparks or splatter produced by the welding, chipping, and/or grinding operations.
The welds shall be free from cracks, porosity, undercut, and incomplete fusion. All weld quality shall conform to ANSI/AWS D14.3.
1. Fabricate a plate to the dimensions in Illustration 1 from 6.0 mm (.24 in) thick ASTM A36 steel.
Illustration 1
Dimensions listed in Chart 1.
2. Drain oil from differential case.
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Fluid Spillage Containment Care must be taken to ensure fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Tools and Shop Product Guide", for tools and supplies suitable to collect and contain fluids in Caterpillar machines. Dispose fluids according to local regulations and mandates.
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3. Following the procedure listed in the appropriate Service Manual, remove the left hand tandem.
4. Wipe clean the remaining oil inside the differential case to prevent weld debris contamination. Cover the differential with heat resistant cloth.
5. Mark the location of the baffle plate with the dimensions from Illustrations 2 and 3.
Illustration 2.
View from rear. (E) 90 mm (3.5 in). (F) 25 mm (1.0 in) of no weld.
Illustration 3.
View from top. (G) 90 mm (3.5 in).
6. Apply one tack weld to the top of the plate, ensuring the plate is vertical, and tack to the rear of the case.
7. Finish weld with 3 welds 30 mm (1.2 in) long on top and 1 weld 25 mm (1.0 in) on rear. Do not weld lower than 25 mm (1.0 in) from the bottom (as shown in Illustration 2).
8. Clean the bottom of the case of any weld slag, using a magnet to remove microscopic debris.
9. Follow the procedure in the appropriate Service Manual to install the left hand tandem. Fill the case with the proper fluid to the proper level. Run the machine and check for leaks.