COUPLING-PERMANENT 1241890 - Caterpillar

All D379, G379, D398, G398, D399 and G399 EnginesThe bolt-on counterweights used on crankshafts for the above engines are now available for parts service. After installation of the new counterweights on the crankshaft, the crankshaft must be balanced. The procedures for balancing vary depending on the balancing machine used. Because different machines can use different principles for determining an unbalance condition, and there are different methods for determining the amount and location of the required correction, it is not practical to give a step-by-step balancing procedure. Use the instructions provided by the manufacturer of the balancing machine for this information. Use this instruction for specifications and general guidelines.General Specifications
(1) The crankshaft must be dynamically balanced to within 3.6 gram-meters (5 oz-in) measured at each end.(2) D379 and D398 crankshafts must be supported at the outer-most main bearings.(3) To prevent whipping, D399 crankshafts must be supported at main journals No 2 and No. 8 (the second main journals in from the ends).(4) Always rotate the crankshaft at a speed, between 200 and 300 rpm, where the drive motor resonance is zero.(5) Always install counterweights with the part number toward the main journal.(6) Put 2P2506 Anti-Seize Compound on the seat and threads of the counterweight bolts. Do not dip the bolts in the compound. Tighten the bolts to a torque of 217 14 Nm (160 10 lb-ft).Balancing Information
(1) If an outer counterweight is being replaced, it should be possible to balance the crankshaft by machining only this counterweight.(2) If an inner counterweight is being replaced, it may also be necessary to replace both outer counterweights. Because the outer counterweights are usually machined at the factory, it may not be possible to remove additional material.(3) The preferred method for balancing the crankshaft is to force a heavy or positive (+) condition to the outer counterweights, then balance to zero.(4) If there is a heavy or positive (+) condition in the center of the crankshaft, remove material from the inner counterweights until the reading is zero or negative (-) [this indicates a light condition]. This will force the positive (+) unbalanced condition to the outer counterweights where it is much easier to balance the crankshaft to zero.(5) When an inner counterweight is machined, it will affect the readings at both outer counterweights. When an outer counterweight is machined, it affects only that counterweight. Therefore, it is always easier to balance the crankshaft by machining the outer counterweights.(6) When the force of unbalance is such that the angular location of the resultant force does not come out on a counterweight, it will be necessary to remove material from other counterweights in order to move the angular displacement so it comes out on the counterweight. [If the corrective angle is in space, it must be forced one way or the other so it comes out over a counterweight. The counterweight can then be machined to balance the crankshaft.](7) Always work the negative (-) unbalance condition from the crankshaft before the positive (+).Machining