View Full Version : GM gearsets data?

08-01-2007, 10:33 AM
Our 10 bolt 7.625 ring gear is interchangable with the 7.5 ring gear,both use 7/16-20 left hand bolts and they both fit on a common carrier.The pinion for either gearset is 27 spline.The only potential difference is 26 or 28 spline axles,but axle splines are not the purpose of this info gathering thread.
The GM 8.2 and 8.5 gearset ring gears have the same bolt pattern location but differ in bolt size.The ID of the 8.2 and the 8.5 are the same so they will fit on the same carrier but because of different bolt sizes only one is correct.
The GM 8.2 uses 3/8-24 right hand bolts and its' matching pinion has 17 splines on it.
The GM 8.5 uses 7/16-20 left hand bolts and its' matching pinion has 30 splines on it.
Now to the purpose of this thread,for the popular "12 bolt" rear end used as replacement for our weak 10 bolts,what is the data compared to the above data.
nominal ring gear diameter?
bolt data-diameter,thread pitch,and LH or RH?
number of splines on the pinion?

08-01-2007, 11:04 AM
There is no difference between a 7.5 and 7.6 ring gear. The look of the pinion shaft changed, but that was it. The 7.6 was mainly just for internal use at GM to distinguish the different cases and axle splines.

The 12 bolt is an 8 7/8" ring gear, 3/8" x 24 RH threads, 1.625 30 spline pinion. But all of that really means nothing. The 8.8 uses the exact same bearings on the pinion and carrier, and so does the late 10 bolt 8.5/8.6. The actual bolt count has almost no effect on strength, it is just used to identify them.

08-01-2007, 11:14 AM
That was the purpose of my thread,to seek identifying data not strenght data.
So a "12 bolt" has a 8 7/8 nominal diameter ring gear,uses 3/8-24 RH bolts,and its' corresponding pinion has 30 splines.

08-01-2007, 12:35 PM
Axle spline is also 30 and the carrier bearings are 3.062 od. GM 8.5" and 8.875" share the same inner and outer pinion bearings.