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rear end gear pontiac firebird.

2K views 7 replies 5 participants last post by  AndersonRacing44 
#1 ·
ive done a little research on my 72' pontiac (formula 350 2bbl carb.) and im pretty sure it came with a 2.73 rear gear. what would be a decent gear to give me a little more launch but still cruise the freeway at a half decent RPM?

the drive tran isnt stock anymore, 4bbl Q-jet carb and a 4-speed M-22 trans.
 
#2 ·
The 8.5" 10-bolt has a 3.23 rear gear available, I've used it, it makes a decent peppy road gear that doesn't rpm too hard on the freeway. My set up was 2.43 low gear ST-10 4 speed and the 3.23 gear and 26" tire, in a Nova. About 2300 rpm at 65 mph IIRC. Nice gear for travel to car shows around the state.
 
#7 ·
big gear head said:
Eaton makes a very good Posi for the 8.5 10 bolt rear end. There is also the Duragrip, which is a copy of the Eaton with Rabestos clutch material instead of the carbon fiber. The Duragrip is about $65 less than the Eaton.
I have given my Eaton posi total hell behind my old 400 Pontiac and my neq and nasty 455 Pontiac. 8.5 30 spline posi is quite tough. Remember that Pontiacs are low end torque motors, not high RPM HP motors, 3.23 will be fine.
 
#8 ·
wow so it sounds like ill be going with the 3.23, the track i race at also has a 1/8 mile drag strip so it will be nice to cruise the hour down there and do some thursday drags!

I think the 3.23 will go nice with the 455 im building. its going to be around 10:1 and pretty radical on the cam so i wont be running to high in RPM.
 
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