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Old 02-17-2013, 09:11 PM
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12 bolt pinion

have read many posts about this topic, 12 bolt car gears in the 12 bolt truck housing using the truck carrier, everyones talking about the conversion bearing. But for my application, the truck pinion size is just fine. just needing the 3.55 ratio the car has. cant find the car housings anywhere, so im using the truck. circle track street stock application so im mandated by the gear rule. 3.55. so back to my main point, does it make sense to just turn the car pinion down to the truck size and run the truck bearing? it does to me, but im open to comments. thanks.

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Old 02-17-2013, 09:26 PM
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Quote:
Originally Posted by justaracerdude View Post
have read many posts about this topic, 12 bolt car gears in the 12 bolt truck housing using the truck carrier, everyones talking about the conversion bearing. But for my application, the truck pinion size is just fine. just needing the 3.55 ratio the car has. cant find the car housings anywhere, so im using the truck. circle track street stock application so im mandated by the gear rule. 3.55. so back to my main point, does it make sense to just turn the car pinion down to the truck size and run the truck bearing? it does to me, but im open to comments. thanks.
Never turned down a car pinion to fit a truck diff, but there's 3.42 gear sets for the 12-bolt truck, that's less than a 4% difference.

You might want to consider using a corporate 10-bolt rearend housing and diff if you just have to have the 3.55, the 10-bolt has the same diameter pinion as the car 12-bolt as I'm sure you know. That is a strong rearend, especially using 30 spline axles.
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Old 02-17-2013, 09:59 PM
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"Turn down" the pinion gear. Not a simple task. Did one on my crank grinder once.
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Old 02-18-2013, 06:58 AM
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As far as I know there is no 3.55 for the 8.5 10 bolt either. The pinion gear is very hard and simply turning it down will not be easy. Even with a carbide cutter it will be very hard to do. Grinding it will take a lot of time. You could use a 8.8 Ford rear end.
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Old 02-18-2013, 07:41 AM
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You're right, I was confusing the 8.2 10-bolt w/the 8.5. My mistake.
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