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It will rev higher and speedo will be incorrect by approx 27% on a 3.9 assuming present diff is 3.08.Either 3.7 or 3.9 will make a big difference in pickup etc
Yip done diff ratio changes on my previous commodore so aware of that, not sure how you go about doing speedo correction on vt v6 but on my old vx ss the tuner was able to adjust it via the ecuIt will rev higher and speedo will be incorrect by approx 27% on a 3.9 assuming present diff is 3.08.
edited for correct %
Scanner to change the pulse count in the cluster.Yip done diff ratio changes on my previous commodore so aware of that, not sure how you go about doing speedo correction on vt v6 but on my old vx ss the tuner was able to adjust it via the ecu