Engine Vibration after Engine or Crankshaft Replacement - kw 2.8 3.5 4L60E crankshaft flexplate flywheel GMT355 idle L52 LK5 M30 repair rough shake transmission

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

Some 2004 - 2005 Colorado and Canyon trucks with an automatic transmission may experience an engine vibration after the engine or crankshaft has been replaced. Typically, the vehicle will exhibit an idle shake and a vibration all the way up to 2,500 RPM. The idle shake may also be worse when the transmission is in drive or reverse. Typically, the engine will exhibit a 1st order engine vibration that is improved when the torque converter to flexplate bolts are temporarily removed for diagnostic evaluation.

The 2.8L and 3.5L engine has a flexplate locator pressed into the center of the rear crankshaft flange to center the flexplate to the crankshaft. However, replacement engines and crankshafts do not include this flexplate locator. Instead, the center of the rear crankshaft flange is machined to accept a replaceable flexplate locator (auto transmission) or clutch pilot bearing (manual transmission). This allows automatic and manual transmission equipped vehicles to use the same replacement engines and crankshafts. If the flexplate locator is not transferred from the old engine to the new replacement engine, an engine vibration may be encountered.

If the SI diagnostics did not isolate a concern and the vehicle recently had the engine or crankshaft replaced, the flexplate locator should be transferred from the original engine or crankshaft. To do this, remove the locator from the original engine by following SI Document # 1197333 and then install it into the replacement engine by following SI Document # 1197337. If the original flexplate locator is no longer available, install a new flexplate locator, part number 12587549, by following SI Document # 1197337. Pictures of necessary J-Tools can be viewed in SI Document # 1042140.

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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.

(04 05 Chevrolet Colorado with an Automatic Transmission) and (04 05 GMC Canyon with an Automatic Transmission)

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