GMC 12635427 Chain Assembly, Water Pump & Balancer Shaft

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Start by disconnecting the negative battery terminal and draining the engine oil to remove and inspect the balance shaft chain and balance shafts. The timing chain, timing chain guides, and sprockets will be removed with engine at TDC for cylinder number 1. Remove the upper balance shaft chain guide, small balance shaft chain guide, adjustable balance shaft chain guide, and finally the balance shaft chain tensioner. Then take out the balance shaft drive chain as well as if needed, the balance shafts (note that removing the shaft requires pulling out engine from vehicle and replacing bushings needs automotive machine shop). Check for wear or damage on components and replace any damaged parts as necessary. In installing, ensure crankshaft timing mark is in proper position at 6 o'clock. Install both of them into their bores and then tighten down retainer bolts. Locate arrows up and down on each sprocket used as a marking point for balancing areas make sure they neither move nor rotate by inserting drill bits through holes provided in both sides of each sprocket. Installing the balance shaft chain would involve aligning with colored links with marks on sprocket followed by resetting its tensioner. Timing marks should be rechecked after which the timing chain together with all parts previously removed should be re-installed. After these have been done reconnect battery cable positive side first while negative lastly before putting back oil filter, filling crankcase with oil again before starting up car and check if there are leaks anywhere inside it when running. Remember that unless you are an expert in this area do not attempt to remove any of these shafts because generally it means taking engine out of vehicle which becomes more complicated task to deal with.

A note at the end stresses that this is a delicate procedure and if undertaken, the engine must be removed from the vehicle although care should be taken since replacement of balance shaft bushings needs a professional machine shop. The removal starts with disconnecting the negative battery cable, draining the oil in the engine, detaching of sprockets, guides and timing chains as well as ensuring that the engine is in TDC for cylinder number 1. Also, chain tensioner and guides of balance shaft are removed after which balance shaft drive chain is released. When removing balance shafts (engine removed), remove balance shaft retainer bolts so as to pull them out carefully from the engine block with caution to mark them for proper reassembly. Various components need to be inspected for damage or wear. The most important thing when installing is to ensure that number one piston is at TDC given that crankshaft has been rotated. Then tighten balance shaft retainer bolts once balance shafts are installed into engine block. This part explains how to align a set of sprockets of balance shaft and how chain fits them using locating marks and colored links on them as references. It consists of installation of chain guides, resetting and reinstalling balance shaft chain tensioner, checking timing marks etc. Finally, put back both timing chain and all other components you had removed earlier then reconnect battery.