The gear-type oil pump, see Figure
, is mounted to the front bulkhead of the balance support and is gear driven from the front end of the crankshaft through the oil pump idler gear.
Effective with engine serial number 4R25678 manufactured on September 18, 1998, an improved oil pump and balance shaft assembly is used. The oil pump assembly can be identified by the increased material thickness in the bolt hole location.
Oil Pump Mounting
The drive gear is pressed on the driveshaft, which is supported inside the housing on two bushings. The driven gear is pressed on the driven gear shaft, which is supported inside the housing on two bushings.
A plunger-type relief valve is attached to the adaptor at the end of the oil supply tube. The relief valve bypasses oil back to the pan when the pressure in the pump exceeds 724 kPa (105 lb/in.2
After testing is completed, finish assembly of oil pump as follows:
Press cups in idler gear to snap ring.
Tool J 39769
is a holding tool only. Do not torque.
Install the idler gear, shaft, and tapered roller bearings cone and spacer in the pump housing.
Align the teeth of the idler gear, so that the "Y" on the gear and the "Y" on the drive gear are aligned.
Using tool J 39769
, hold the shaft in place, and torque the left-hand threaded bolt to 199-231 Nm (147-170 lbft).
Check the gear lash between gears. Lash should read 0.051-0.203 mm (0.002-0.008 in.). See Figure
Checking Gear Lash
Installation of Oil Pump
Perform the following steps to install the oil pump:
Install the oil pump, taking care to match each of the letters stamped on the oil pump idler gear and oil pump drive gear with the same letter of the left and right side balance shafts. See Figure
Balance Shaft Drive Gear Timing
When all the gears are aligned correctly, install the M8 bolts and torque to 34 Nm (25 lbft).
Install the four M8 bolts that attach the oil pump to the balance support and torque to 34 Nm (25 lbft).
To aid balancer timing, leave the oil pump gear holding tool J 39816
in place until the balance assembly is installed in the engine.
Install new o-ring seals on both ends of the oil pump outlet tube and lubricate them with clean engine oil.
Loosely assemble the left and right side oil inlet tube brackets to the inlet tube using the M10 nuts and bolts.
Install one end of the oil pump outlet tube into the inlet tee, the other into the pump body.
Install the inlet tee and attach the relief valve using two M8 bolts and torque to 34 Nm (25 lbft).
Install the regulator valve using two M8 bolts and torque to 34 Nm (25 lbft).
Install the two M10 bolts that attach the left and right side oil inlet tube brackets to the support and torque to 47 Nm (35 lbft).
Tighten the M10 bolts and nuts that fasten the tube bracket assembly to the inlet tube.
Attach the balancer assembly to the transmission jack stand J 39814
Use guide studs in opposite center holes to properly align the balance shaft support.
Before attaching the balance shaft assembly to the block, make sure the timing marks are aligned correctly. See Figure
Oil Pump Torque Sequence
Raise the balance shaft assembly to the cylinder block and attach it using the nine M12 bolts and torque to 115 Nm (85 lbft).
Remove guide studs and install remaining two M12 bolts and torque to 115 Nm (85 lbft).
Remove the oil pump gear holding tool J 39816
from the balance shafts.