The Stovebolt Site Forums The Parking Lot '60-'66 Trucks 12 bolt rear ends

Is there a difference between 12 bolt car and truck rear ends? I have a new complete 4:56 set up for a chevelle, will it fit my 66 truck 12 bolt? truck now has open 3:73

truck is diff from car, IIRC.

the car ring & pinion can be installed in the truck rears. Ive did it.

Summit Racing lists them different, but I don't know what the difference is.

cm

There are also different size carriers for the 12 bolt. One excepts shorter gears and one excepts taller gears

ring gear sizes there are 8 and 8 1/2" sizes

Yes the carriers are different the 3 series carriers will accept ratios from 308 to 390. the four series from 410 to 488. you can use a spacer to install 4 series gears on three series carriers. You gotta know what your doing to set up a rear end. If you dont get it right it will sound like a siren and wear out quickly.

there is a difference in the carrier bearing size to. you can go onto a differential web site a look. there is more of a difference than just the gears. there are different carriers 1,2,3 for different gear ratios also.

Those are 10 bolts. The 12 bolt is an 8 7/8".

GM 12-Bolt
Two versions of the GM 12-bolt exist but have nothing more than the bolt count in common. One is a car version with a grooved cover plate, while the truck-version cover plate is raised. The 12-bolt is integral and semifloating, but isn't a big step up from the 8-1/2-inch 10-bolt because the axleshafts and housings are very similar. A drawback to both the 10- and 12-bolt axles is that the axleshafts are retained by C-clips, which, if broken, can be a serious hazard.
Applications: '64-'82 K10/K20 and Blazer
Ring-gear diameter: 8.875 in
Pinion-gear diameter/splines: 1.438/30 splines
Available gearsets: 3.07, 3.42, 3.73, 4.10, 4.56, 4.88, 5.13, and 5.38

Also in 3.90:1, 4.11:1 according to the 63 assembly book