The crankshaft timing gear is a helical gear that is indexed to the crankshaft by a key. It is pressed onto the end of the crankshaft. The inside diameter of the 12.7 liter engine crankshaft timing gear is slightly larger than the 11.1 liter engine gear. The current 12.7 liter engine gear can be identified by an "O" on the front face of the gear. See Figure
The former 12.7 liter engine gear had a groove on the front face.
1. Timing Gear, Crankshaft
4. Timing Wheel, DDEC II
2. 12.7L Gear
5. Timing Wheel, DDEC III
3. 11.1L Gear
6. Woodruff Key
Crankshaft Timing Gear and Related Parts
The crankshaft timing gear directly drives the bull gear and oil pump drive gear. The bull gear drives the various accessories, and drives the camshaft through the idler gear. See Figure
Engine Gear Train
A timing wheel is installed on the crankshaft directly behind the crankshaft timing gear. The timing wheel is indexed to the crankshaft by the same key as the crankshaft timing gear, and is retained to the crankshaft by the crankshaft timing gear. The timing wheel is marked with the word OUT on the outboard side, and should be installed with this mark facing you as you install the wheel. See Figure
Crankshaft Timing Gear and Related Parts Location
The timing wheel induces a voltage signal in the Timing Reference Sensor (TRS), as the teeth of the pulse wheel passes by the TRS. This signal is sent to the Electronic Control Module (ECM) to determine injector firing.
Since the crankshaft and camshaft must be in time with each other, a series of timing marks are stamped or etched on the faces of the gears in the gear train. Refer to section
, for gear train timing information. The balance shafts and crankshaft must also be in time with each other.
The crankshaft timing gear is lubricated by splash from the engine oil pan, and excess oil returning to the oil pan from the other gears.
Repair or Replacement of Crankshaft Timing Gear and Timing Wheel
To determine if repair or replacement of the crankshaft timing gear and timing wheel are necessary, perform the following procedure. See Figure
Flowchart for Repair or Replacement of Crankshaft Timing Gear and Timing Wheel
Removal of Crankshaft Timing Gear and Timing Wheel
Remove the gear and the timing wheel as follows:
Installation of Crankshaft Timing Gear and Timing Wheel Installation Tools
If removed, install the key to the keyway. Tap the key with a plastic mallet or brass hammer to seat. See Figure
Index the keyway of the timing wheel with the key in the crankshaft. Slide the timing wheel onto the crankshaft, with the word OUT on the timing wheel facing you, as far as it will go without forcing it. See Figure
Timing Wheel Installation
Coat the bore of the crankshaft timing gear with a film of Lubriplate.
Index the keyway of the crankshaft timing gear with the Woodruff key in the crankshaft. Tap the gear with a plastic hammer or fiber mallet, to ensure that the key is started in the keyway. See Figure
Install the three retaining nuts to the puller legs. Thread the nuts past the first set of threads on the legs. Slide the nuts past the unthreaded portion of the shafts, and engage the second set of threads. Tighten but do not torque the retaining nuts. See Figure
Close the valve on J 35951-175
. Work the pump handle to supply hydraulic pressure to the ram. Make sure that the slot in the crankshaft timing gear indexes with the key in the crank. Pump until the crankshaft timing gear is seated firmly against the timing wheel and the timing wheel is seated firmly against the crankshaft flange. See Figure
A minimum force of 30 kN (3.37 tons) must be obtained when pressing the gear on the crankshaft.