Engine Vibration and Knock from the Rear of the Engine - kw 2.8 LK5 balance block chain crank GMT355 idle information no noise oil rough shaft

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Some 2005 Colorado and Canyon trucks that are equipped with a 2.8L (VIN 8 - RPO LK5) inline engine and built prior to VIN breakpoint 58162872 (Last 8 of VIN), may experience a knock from the rear of the engine and an internal engine vibration. Upon inspection, the rear bearing of the left balance shaft may show abnormal wear or it may be seized. A seized left balance shaft may cause the balance shaft chain to become mistimed or to fall off of the sprockets entirely. This may be a result of reduced lubrication to the rear bearing of the left balance shaft due to a mis-located rear balance shaft bearing oil galley.

If the vehicle experiences any of the above conditions and the last 8 of the VIN is prior to 58162872, perform the following inspection (For all others, follow normal SI procedures and repair as necessary.):

1. Inspect the engine block casting date by looking between the power steering pump pulley and the power steering pump bracket, just to the rear of the engine front cover. It may be necessary to trim off some of the excess front cover sealer in this area to expose all of the numbers. If the casting date is 081904, continue to step 2. If the casting date is NOT 081904, follow normal SI procedures and repair as necessary.
2. Inspect the Foam ID by raising the vehicle, turning the steering wheel to the full left position and looking between the right front frame rail and the right front, inner fender splash shield. It will be necessary to stand at the rear of the right front tire while using a mirror and a flash light to inspect the Foam ID. The Foam ID is stamped between the two rear oil galley plugs that are directly above the right balance shaft casting area of the engine block. If the Foam ID is A1 AND the casting date above was 081904, contact PQC (Product Quality Center) at 1-866-654-7654 for warranty claim authorization and replace the engine. Be prepared to report the Foam ID and casting date to PQC. If the Foam ID is NOT A1, follow normal SI procedures and repair as necessary.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

(05 Chevrolet Colorado S1 T1) and (05 GMC Canyon S1 T1)

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