Did anyone notice in that article that there were a couple of mistakes?
They state the ring gear dia. of a 12 bolt is 8.375......NOT!
Also they state that ALL 8.5 ten bolts use 28 spline axles.......NOT!
If you find an 8.5 posi out of an 88, or 89+ chevy full size pickup, you'd better count the axle splines B4 shelling out $$$ because it most likely will be a 30 spline unit. Also, I've determined that the worst thing Chevy did was go to the 30 spline axles in the full size pickups & Suburbans. I had 4 of these this last week with the left (ring gear side) carrier bearing spun on the carrier. One was completely snapped off the carrier. These were all open diffs, and we stock the open carriers just for this reason. If going to a posi in a 30 spline vehicle, get the Eaton posi with the larger carrier journals and special carrier bearings, it's worth the extra money.
The reason these factory 30 spline units are weak, is this:
To allow for the larger axle diameter, chevy made the internal part of the journal wider, but left the outer diameter the same, resulting in a thinner bearing journal. This thinner journal allows the inner race of the bearing to spin on the journal after many miles of use. This bearing should be a press fit. When this happens, the only cure is a new carrier, and if it's a posi it means more $$. I have only seen this on the 30 spline units, not the older 28 spline ones.
Sorry for the windy message, but thought people sould know.
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70 & 1/2 RS Camaro
SB406 & M20 4spd
9" Rear
70 Malibu
SB350 & TH400
Gold Member # 103
Driveline Technician
[This message has been edited by Scooter (edited 12-24-1999).]