To lose 2/10s in 60ft. and lose 4 mph in the 1/4 mile is a lot . You’ve lost it on both ends. Hard to believe only going from a 3.36 gear to a 3.70 would affect 60 ft so much and to blame it all on the gear change. And you went with a taller tire which would have cancelled out some of that gear change. Something else has to be going on here. Is that new rear end robbing horsepower compared to the other rear?
Also you might not feel a complete loss of power at the other end but still be running out of fuel. For the heck of it you can hook up a temporary fuel pressure gauge to see if you’re dipping below 4 psi or so at the other end. Not saying that’s your problem, but it’s always nice to know that information.
They say going from a c4 trans to a c6 robs about 20-30 hp just because of the internals.
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72 lemans,455 e-head, UD 255/263 solid flat,3.73 gears,,,10" 4400 converter,, 6.68 at 101.8 mph,,1.44 60 ft.2007
(cam 271/278 roller)9"CC.4.11gear 6.41 at 106.32 mph 1.42 60 ft.(2009) SOLD,SOLD
1970 GTO 455 4 speed #matching,, 3.31 posi.Stock manifolds. # 64 heads.A factory mint tuquoise ,69' judge stripe car. 8.45 @ 88.1 mph on slippery street tires.Bad 2.19 60ft.Owned since 86'
Last edited by scott70; 07-23-2025 at 07:44 AM.
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