SOFTWARE GP-MONITOR 5677458 - Caterpillar

--------------- END SUPPLEMENT ---------------Reference: Service Magazine; September 8, 1986; Page 6; "Indications Of Engine Overspeeding When Only One Cam Lobe/Lifter Has Failed." Service Magazine; November 2, 1987; Page 6; "Results Of High Speed And/Or Overspeeding Of 3406B Truck Engines."Description of Change: Self-locking bolts are now used in the front timing gear groups on all 3406B Engines. The new self-locking bolts replace the former standard bolts used to fasten the front idler gear shaft to the cylinder block. See the illustration. The new self-locking bolts are installed with a higher torque than the former bolts. These changes eliminate the need to check and tighten the bolts when the engine is subjected to a minor "overspeed." Overspeed is defined as engine rpm greater than high idle. If engine overspeed has resulted in related damage (bent push rods, valve to piston contact, or any other visible valve train damage), the tightness of the self-locking bolts should still be checked. Any time the front idler gear shaft is removed, the self-locking bolts should be replaced.
Location of the new 308535 Self-Locking Bolts.Adaptable As: The new 308535 Self-Locking Bolts are direct replacements for the former OL1351 Bolts in the front timing gear groups used on 3406B Engines. Five 308535 Self-Locking Bolts are used to fasten the 4N345 Drive Idler Shaft to the cylinder block. Tighten the 308535 Self-Locking Bolts to a torque of 55 7 N m (40 5 lb ft).