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1999 silverado engine swap fit

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I have a 1999 silverado with a 4.8 engine and 5 speed manual transmission. I would like to use a swap engine from a 2004 and notice that there is a difference in crankshaft flange size. I want to know how does it affect me changing or if I can?


  • The 1999-2000 LR4 with a manual transmission had a crankshaft with a 1.250 in. long rear flange. (Casting #12553312)
  • All other LR4 engines had a crankshaft with a 0.857 in. rear flange. (Casting #12553482)

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Best bet would be to call a Salvage yard as they can tell you interchangeability in regards to various year models. Only certain year models are compatible with certain year models. 

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