Thread: 4x4 12 bolt
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Old 07-27-2010, 09:00 AM   #4
68 TT
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Re: 4x4 12 bolt

Quote:
Originally Posted by nbpro View Post
1987 chevy 4x4 12 bolt rear end with 3.73 gears with 31 spine axles

swap in to a 1981 gmc with a 305 engine. 10 bolt 2.56 gears th350c transmissions
Are you sure it has 31 spline axles? I thought the 12 bolt had 30 spline and the pre-new body style 10 bolt had 28 spline.

The 12 bolt has an 8.875" diameter ring gear and the 10 bolt is 8.5". I don't think the gears will swap between the two.

You can easily find a 5-lug rear end that will fit your truck with better gears or just get the gear set & carrier from a wrecking yard and put it in your existing rear end.
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