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Hummer 12646387 Timing Chain

2003-2010 Hummer

Customer Questions & Expert Answers (2)
12646387 GM Timing Chain Product Photo 1 of 1
  • Part Description
    Chain, Engine Timing
  • Manufacturer
    General Motors
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  • Q&A
  • Product Specifications

    BrandGenuine Hummer
    Manufacturer Part Number12646387
    Part DescriptionTiming Chain; Chain, Engine Timing
    Item Dimensions9.7 x 6.3 x 0.7 inches
    Item Weight0.90 Pounds
    ConditionNew
    Fitment TypeDirect Replacement
    ManufacturerGeneral Motors
    SKU12646387
    WarrantyThis genuine GM part is guaranteed by GM's factory warranty.
    Shipping & ReturnShipping Policy Return Policy
    Warning: California's Proposition 65
  • Vehicle Fitment

    Year Make Model Engine Important vehicle option details
    2003-2009 Hummer H28 Cyl 6.0L, 8 Cyl 6.2L, 8 Cyl 6.2L FlexH2 HUMMER, PICKUP, SUV
    2008-2010 Hummer H38 Cyl 5.3LCREW CAB, SUV
    2009-2010 Hummer H3T8 Cyl 5.3LCREW CAB, SUV
  • Customer Questions & Expert Answers

    Q:
    I'm wondering if this is complete and correct part for my vehicle.
    A:
    You can Select Your Vehicle to check if 12646387 fits your vehicle.
    Posted and answered by GM Parts Specialist Julian
    Q:
    How to disconnect the battery and replace the Timing Chain in V8 engine on Chevrolet Trailblazer? Posted by Tevin B.
    A:
    Remove the battery cable from the negative terminal, and drain out the cooling system and the engine oil, and then remove the upper and the lower fan shrouds, drivebelt, cooling fan and the water pump. Eliminate the crankshaft balancer and also the oil pan in order to access the bearings. For the 2005 on models, remove the mounting bolts and the camshaft position sensor comes off as well. Remove the mounting bolts that secure the timing chain cover and, in case this requires additional force, use a putty knife to loosen up the gasket but without harming the aluminum piece. The oil pick-up tube and the oil pump should be removed to take measurements of the timing chain freeplay; anything over 5/8 of an inch should have a new chain and both sprockets put in. The next steps are to slack off the camshaft sprocket bolts, turn the crankshaft so that its timing mark is in line with the number one cylinder and make sure number one piston is also at TDC. Take out the bolts that are at the end of the camshaft, and, therefore, the camshaft sprocket and the chain. For 2005 on models, the timing chain damper will have to be removed. Check the camshaft and crankshaft sprockets of its fitness to proceed, if required, remove the crankshaft sprocket gently. While your car is still off, turn the engine by gripping the top of the crankshaft to feel for any form of push back at least turn it two more times. Timing chains should be replaced in sets with the sprockets and gasket scraper should be used to remove old materiel from the cover and engine block. Bolt the timing chain damper and then engage the crankshaft sprocket with the Woodruff key, and then push on to the crankshaft. Thread the new chain through the front and rear sprockets so the timing marks line up and apply a thread locking compound to the sprocket bolt threads before torquing the bolt. Oil the chain with clean engine oil, fit in the oil pump and oil pick-up tube and loosely fit the timing chain cover with a new gasket. The timing chain cover doesn't need the oil pan rail be perfect on each end, just make them even, then Tighten the cover bolts. Use RTV sealant round the lower edge of the timing chain cover onto the cylinder block, fit the oil pan on, and do the other components fitting as the instruction in the reverse order. Last step is to put some coolant and oil and start the vehicle and look for the any leakage in the engine.
    You can Select Your Vehicle to see complete installation and repair tips.
    Answered by GM Parts Specialist Jeremy / Apr 28, 2025

Genuine GM Part 12646387, the Right Choice

To ensure reliability, purchase GM part # 12646387 Timing Chain. It is sometimes referred to as Hummer Timing Chain. Directly from GM, genuine parts are superb with regards to quality, longevity, and fit. Every single part passed stringent quality testing, so you can be sure that it's safe, durable, and built to perform like your original parts. This part fits specific Hummer H2, H3, H3T models.

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