Thread: 10 bolt, 12 bolt, rear ends -- explanation?

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Just learning here so roll with me...

What is the difference, other than cosmetic, of a 8, 10, or 12 bolt rear end? By seeing the number of bolts can you determine what the differential is? Is there a preference for a 1/2 ton truck?

Appreciate it,
Andy

The quickie answer is that, for GM products, the number of bolts refers to the number of bolts that retain the ring gear to the carrier inside the rear end. However, some clever GM Engineer also designed the cover bolt pattern to contain the same number of bolts...a 10 bolt ring gear has a 10 bolt cover, etc. There is no 8 bolt ring gear in a GM car or truck. There is, however, a 14 bolt rear end in later model 3/4 ton pickups.

The number of retaining bolts signifies the relative strength of the rear axle....more bolts indicates that the axle can transmit more torque. Ther are zillions of Chevy pickups running with 10 bolt rear ends...what is your intended use and engine size? A mild street truck is fine with a 10 bolt while a bigger pickup towing a heavy travel trailer may have problems.

Just like a "4 bolt main" block, the high-school mentality is that a 12 bolt axle is a must for a pickup......but do you always need a one? Let your intended use be your guide.

mike in tucson

So the bolt number has nothing to do with telling what the differential's gear ratio is within, just simply a matter of construction stability. Appreciate it.

Correct, the axle gearing ratio has zero to do with the number of ring gear bolts or cover bolts.

The most positive way to figure out the ratio is to remove the cover and count the number of teeth on the ring gear and on the pinion gear and divide the ring gear count by the pinion gear count. There is another method (that will get you close) that involves rotating the driveshaft by hand and counting the revolutions of the tire. If the rear axle has an "open" (or non limited slip) carrier, the procedure requires that one tire is held from rotating.....you can probably Google to find a more detailed instruction.