TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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Table 6-9. Connecting Rods, Crankshaft and Associated Parts Overhaul Standards - Continued Fig. Ref. Sizes and fits Component No. letter Point of measurement of new parts Wear limits B-4 RR Outside diameter of split sleeve bearing must be press fit in bore. Burnish to seat sleeve bearing prior to finish diameter B-4 SS Inside diameter of bushing-type sleeve bearing 2.0025 2.0027 2.0040 B-4 H Outside diameter of piston pin 2.0000 2.0002 B-4 SS-H Fit of pin in bearing 1.9998 0.0023L 0.0027L 0.0042L Note. Refer to paragraph 6-3b for explanation of symbols. 6-17. Repair a. Crankshafts. (1) Replace crankshafts that are deeply scratched, nicked, burred, scuffed or galled. Minor imperfections in the journals may be repaired by polishing with a crocus cloth dipped in dry-cleaning solvent or mineral spirits paint thinner. (2) Crankshafts that are worn beyond standard wear limits specified in the overhaul standards (table 6-9) or with journal or crank- case damage may be ground undersize to the limits established for crankshaft rework (table 6- 9). (3) In the event any of the crankpins or journals are found unserviceable, it will be necessary to polish or grind all crankpins or journals uniformly undersize to maintain the balance of the crankshaft. Extreme care must be taken when regrinding, to maintain the con- centricity of the entire crankshaft and not to exceed a surface roughness of 12 micro inches. All radii on the crankpins and journals, effected by grinding undersize, must be re-established to original configuration. The crankshaft nitride finish of crankpins and journals must be in- spected by magnaflux or similar method for fractures and surface cracks after finishing. (4) Replace dowel pins (18 fig. B-3) and straight pins (25) in crankshaft flange if pins do not fit securely in flange, are out-of-round or if pins do not conform to limits specified in the overhaul standards (table 6-9). Note. The headless grooved dowel pins in the flywheel end flanges are available in 0.005 and 0.010 in. oversize. Ream crankshaft flywheel mounting flange to necessary oversize dimen- sions and install new pins. Whenever oversize pins are used, it will be necessary to ream the flywheel and transmission drive gearshaft ac- cordingly. (5) Replace a cracked crankshaft or a crankshaft showing evidence of wear due to bent or twisted connecting rods. b. Connecting Rods and Bearings. (1) Connecting rod bolts. (a) Replace bolts that do not fit snugly in rod and cap. (b) Replace bolts that have damaged threads, galled pilot diameters, or diameters that are not within limits specified in overhaul standards (table 6-9). (c) Replace bolts that are cracked or scratched, or that show any evidence of stretching. (2) Connecting rod bearings. Replace all bearings that do not check within limits specified in overhaul standards (table 6-9) or when bearings do not show 75 percent contact by Prussian blue transfer after bore check. (3) Connecting rod assembly. Discard con- necting rods that are bent or distorted. Straightening of connecting rods is not per- mitted. Break and polish sharp edges at con- necting rod counterbore and rod contour (fig. 6- 35). Replace connecting rod assemblies which are not within limits specified in overhaul standards (table 6-9). Connecting rods with worn or damaged piston pin bearing may be repaired. Replace worn or damaged piston pin bushing-type bearing using an arbor press. Bearing split line must be 90 degrees from longitudinal center line. Line-ream new bearing to size shown in overhaul standards (table 6-9). 6-39