General Precautions for Disassembly

TM-5-3820-256-24-5 Drilling System Well Rotary Truck Mounted Air Transportable 600 Feet Capacity Model LP-12 NSN 3820-01-246-4276 Manual
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MAINTENANCE SECTION II General Precautions for Disassembly IMPORTANT Read this section before starting the detailed disassembly procedure. Follow each procedure closely in each section, making use of both the text and the pictures. Rebuild Facilities A suitable holding fixture or overhaul stand is desirable, but not necessary, to rebuild this unit. The flat bottom of the transmission case provides a suitable working platform when the unit is placed on a sturdy shop table. For easier working conditions, table height should be 28- 30 inches A light chain hoist should be used to handle the mainshaft and countershafts during removal and reassembly procedures. Cleanliness Transmissions should be steam cleaned prior to disassembly. Seal all openings before steam cleaning. This will prevent dirt and water entry, which can damage serviceable parts. Dirt is abrasive and will cause premature wear of bearings and other parts. Therefore, we suggest having a small wash tank nearby so parts can be cleaned prior to reassembly. Bearings When a transmission is removed at relatively low mileage, the bearings should be removed with pullers designed for this purpose. Wrap the bearings to keep out dirt. Clean, inspect and lubricate all bearings just prior to reassembly. If mileage or transmission condition warrants a complete overhaul, it is recommended that all bearings be replaced. End Yokes and Flanges End yokes and flanges should be installed and removed with the correct drivers and pullers-not with a hammer. Hammering is not only destructive to the yoke or the flange, but also can cause serious internal transmission damage. For example, hammering destroys or mutilates the pilot diameters, as well as warps or bends the flange. Hammering on end yokes will close in the bearing bores or misalign yoke lugs, resulting in early journal needle bearing failures. In most designs, when the yoke/flange locknuts are tightened and secure, the internal bearings and gears are in proper location. When the yoke/flange is driven on the shaft, however, two conditions can exist. (a) If the bearing fit is tight on the shaft, usually the bearings will brinell since they absorb the pounding force of the hammer. (b) If the bearing fit is loose, the shaft will keep moving inward until it is stopped by the internal parts such as the pilot bearing thrust washers and snap rings. 5

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