GMC 12552128 Sprocket, Camshaft

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To remove and install the timing chain and sprockets, begin by disconnecting the negative battery cable and removing the front cover. Take off the oil slinger from the crankshaft and rotate the engine to align the cam gear timing marks, ensuring the No. 1 cylinder is on the TDC of its compression stroke. From the camshaft, remove the camshaft thrust button and screw, and discard the thrust button. Slide out the cam gear, crankshaft sprocket, and timing chain as an assembly. To install, clean the gasket mounting surfaces and inspect all parts for wear or damage, replacing as necessary. Assemble the timing chain on the cam gear and crankshaft sprockets, align the timing marks on the sprockets to face each other, and align the dowel pin in the cam gear with the index hole in the sprocket; then slide the assembly onto the cam gear and install the sprocket-to-cam gear bolts, tightening it to 37 ft. lbs. Install the new thrust button and the oil slinger, followed by the front cover. Finally, connect the negative battery cable, refill the cooling system, start the engine, allow it to reach normal operating temperatures, and check for leaks.

On certain V6 and small block V8 engines, removing the timing cover may require loosening and lowering the oil pan, potentially necessitating a new gasket if it breaks during the process. Accessories obstructing access to the timing chain cover should be detached and moved aside, and big block engines may involve cutting the oil pan gasket and removing the cover.

On certain V6 and small block V8 engines, removing the timing cover may require loosening and lowering the oil pan, potentially necessitating a new gasket if it breaks during the process. Accessories obstructing access to the timing chain cover should be detached and moved aside, and big block engines may involve cutting the oil pan gasket and removing the cover.