[SD455DJ]

Bruce, I'd opt for a new 3.08 gear behind your 455. I have a new 3.08 gear (Yukon) & Eaton posi unit in the 12-bolt (McKinnon out of a '70 GP) in my '70 Lemans with a 461 with an M-20 4-speed trans. It pulls away easy from a stop in 1st gear and runs at 2650 rpm at 70 mph. With your TH400 automatic, it's a great gear for a 455 with abundance of torque to easily overcome that gear. My brother has a '71 455HO GTO with the factory 3.07 12-bolt that easily runs low 13's and can cruise nicely on the highway.

Dennis

[Bruce Meyer]

Originally Posted by SD455DJ

Bruce, I'd opt for a new 3.08 gear behind your 455. I have a new 3.08 gear (Yukon) & Eaton posi unit in the 12-bolt (McKinnon out of a '70 GP) in my '70 Lemans with a 461 with an M-20 4-speed trans. It pulls away easy from a stop in 1st gear and runs at 2650 rpm at 70 mph. With your TH400 automatic, it's a great gear for a 455 with abundance of torque to easily overcome that gear. My brother has a '71 455HO GTO with the factory 3.07 12-bolt that easily runs low 13's and can cruise nicely on the highway.

Dennis

I was thinking of using 3.08 gears as they are readily available. I am going to a taller rear tire. Either a 27 or 28 inch. With a 3.31 gear and the taller tire I figured the Speedometer would still be accurate. Im leaning towards the 12 bolt either way.

[SD455DJ]

I'm running 27" tall tires (225R70/15's & 255R60/15's).

Dennis