Duramax LLY – Checking Crankshaft Journal Diameter and Runout

There are three main journal diameter ranges. These ranges are identified by a color code paint mark near one of the journals. The three size range color codes are blue, orange/red, and white. Note the code on the crankshaft and refer to the specification charts at the end of this section for size ranges.

Use a micrometer to check journal diameter. Measure both ends of each journal to check for taper along with wear (Figure 2-114).

Journal wear or taper must not exceed 0.0002-0.001 in. (0.05-0.025 mm). Mount the crankshaft in a holding fixture and check runout at center (#3) main bearing journal (Figure 2-115). Crankshaft runout should not exceed 0.0002 – 0.0008 in. (0.005 – 0.020 mm). Replace the crankshaft if runout is greater than specified. Do not attempt to straighten a cast iron crankshaft.




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