1995/08/21 Caterpillar

Caterpillar Machines Powered By 3406, 3408, And 3412 Machine Engines

Reference: Service Magazine; October 3, 1994; Page 9; "New Engine Crankshaft Rubber Damper Assembly Uses Improved Rubber Material"

Both the rubber crankshaft damper and the viscous crankshaft damper should be inspected at intervals as follows:

* 3406 Engines - At 190 000 L (50,000 U.S. Gallons) of fuel used, or 480 000 km (300,000 miles), or 6000 hours.

* 3408 Engines - At 260 000 L (68,000 U.S. Gallons) of fuel used, or 6000 hours.

* 3412 Engines - At 380 000 L (100,000 U.S. Gallons) of fuel used, or 6000 hours.

Rubber Crankshaft Dampers

It is recommended that a rubber crankshaft damper be replaced for any of the following reasons:

* The engine has a broken crankshaft and/or the engine has had a gear train failure.

* The crankshaft front bearing is badly worn.

* The gear train has a large amount of wear that is not caused by a lack of oil.

* Inspection shows slippage (movement), either radially or axially, between the inner and outer members of the damper. [The damper can have visual wobble (movement to the front and rear when in rotation) on the outer ring. This does not mean a replacement is necessary. Some movement of the outer ring is normal.]

* Inspection shows rubber deterioration (cracking, spalling, splitting, etc.).

The rubber crankshaft damper should also be replaced at overhaul or the following intervals, whichever occurs first:

* 3406 Engines - At 380 000 L (100,000 U.S. Gallons) of fuel used, or 960 000 km (600,000 miles), or 12,000 hours.

* 3408 Engines - At 513 000 L (135,000 U.S. Gallons) of fuel used, or 12,000 hours.

* 3412 Engines - At 760 000 L (200,000 U.S. Gallons) of fuel used, or 12,000 hours.

NOTE: The 4P-4297 Damper Assembly should be replaced after 250 000 L (67,000 U.S. Gallons) of fuel used, or 640 000 km (400,000 miles), or 8000 hours.

Viscous Crankshaft Dampers

The viscous crankshaft damper should be replaced for any of the following reasons:

* The engine has a broken crankshaft and/or the engine has had a gear train failure.

* The crankshaft front bearing is badly worn.

* The gear train has a large amount of wear that is not caused by a lack of oil.

* Inspection shows fluid leakage or a dented (damaged) housing. Either condition can cause the internal metal ring to make contact with the housing and result in incorrect damper operation.

If none of the above conditions are found, the viscous crankshaft damper can be used again.