REMOVAL & INSTALLATION
4.5L and 4.9L Engines
- Disconnect the negative battery cable. Remove the front cover.
- Remove the oil slinger from the crankshaft. Rotate the engine to align the sprocket timing marks; the No. 1 cylinder will be on the TDC of its compression stroke.
- From the camshaft, remove the camshaft thrust button and screw. Discard the camshaft thrust button. Slide the camshaft sprocket, the crankshaft sprocket and timing chain from the engine as an assembly.
- Clean the gasket mounting surfaces. Inspect the parts for wear and/or damage; if necessary, replace the parts.
Install the timing chain and sprockets by performing the following:
- Assemble the timing chain on the camshaft sprocket and crankshaft sprockets.
- Align the timing marks on the sprockets; they must face each other.
- Align the dowel pin in the camshaft with the index hole in the sprocket.
- Slide the assembly onto the camshaft and crankshaft. Install the camshaft sprocket-to-camshaft bolts. Tighten the camshaft sprocket-to-camshaft sprocket bolt to 37 ft. lbs. (50 Nm).
- Install the new thrust button and install the oil slinger to the crankshaft.
- Install the front cover. Connect the negative battery cable.
- Refill the cooling system. Start the engine, allow it to reach normal operating temperatures and check for leaks.
Camshaft Primary Drive Chain
- Remove the engine assembly and put it on an engine stand or remove the powertrain assembly.
- Remove the serpentine drive belt, idler pulley and belt tensioner, if not done previously.
- Remove the front cover and oil pump.
- Remove the cam covers.
- Remove the three timing chain tensioners.
- Remove the camshaft sprocket bolt from all four camshafts and remove the sprockets.
- Remove the secondary drive chains from around the intermediate shaft sprocket.
- Remove the one bolt holding the intermediate shaft sprocket and slide the gears and the primary drive chain off the crankshaft and intermediate shaft.
- Retime the camshafts.
- Install the oil pump.
- Install the cam covers.
- Install the serpentine drive belt, idler pulley, and belt tensioner.
- Install the engine assembly or the powertrain assembly.
- Remove the front cover.
- Remove the left side cam covers.
- Remove the left side secondary chain tensioner.
- Remove the left side chain guide. Access the upper chain guide mounting bolt through the hole in the cylinder head covered with the plastic plug.
- Remove the left side cam sprocket bolts and sprockets.
- Remove the secondary drive chain.
- Repeat Steps 2 through 6 if the right side chain is being replaced.
- Retime the camshafts.
- Install the front cover.
- Install the cam cover(s).
SETTING CAMSHAFT TIMING
Setting camshaft timing is necessary whenever the cam drive system has been disturbed such that the relationship between any chain and sprocket has been lost. Correct timing exist when the crank sprocket and the intermediate shaft sprocket have their timing marks aligned and all 4 camshaft drive pins are perpendicular (90°) to the cylinder head surface.
To allow access the following components must be removed:
- Both cam covers.
- Front cover
- The three chain tensioners. The tensioners may be in their installed positions but must be fully retracted.
- The oil pump.
- The primary and secondary chain guides should be reinstalled if previously removed.
- Rotate the crankshaft until the sprocket drive key is at approximately the 1 o'clock position. Use J 39946 to rotate the crankshaft.
- Install the crankshaft and intermediate shaft sprockets to the primary drive chain with their timing marks adjacent to each other.
- Install the crank and intermediate sprockets over their respective shafts.
- Rotate the crankshaft as necessary to engage the crankshaft key in the sprocket without changing the relationship of the timing marks to each other. Use J 39946 to rotate the crankshaft.
- Install the intermediate sprocket retainer bolt and tighten to 45 ft. lbs. (60 Nm).
- Install the primary chain tensioner or release tensioner shoe. Tighten the two tensioner mounting bolts to 20 ft. lbs. (25 Nm).
- Install flywheel holder J 39411 to lock the crankshaft in this position. If the engine is on a stand, an alternate method should be devised.
- Route the secondary drive chain for the right side cylinder head over the inner row of the intermediate shaft teeth.
- Route the secondary drive chain over the chain guide and install the exhaust cam sprocket to the chain such that the camshaft drive pin engages the sprocket notch RE (right head exhaust). There should be no slack in the lower section of the chain and the cam drive pin must be perpendicular to the cylinder head face.
- Install the intake cam sprocket into the chain so that the sprocket notch RI (right head intake) engages the camshaft drive pin remains perpendicular to the cylinder head face. A hex is cast into the camshafts behind the lobes for cylinder No. 1 (or No. 2, LH) so that an open-end wrench may be used to provide minor repositioning of the cams.
- Loosely install the exhaust cam sprocket retainer bolt.
- Loosely install the intake cam sprocket retainer bolt.
- Install the chain tensioner or release tension on the shoe and tighten the tensioner mounting bolts to 20 ft. lbs. (25 Nm).
- Tighten the cam sprocket bolts to 90 ft lbs. (120 Nm).
- Route the secondary drive chain for the left side cylinder head over the inner row of the intermediate shaft teeth and repeat Steps 11 through 16 for left side cams. Left side cam sprockets are identified LI (left intake) and LE (left exhaust).