Whats the deal with the carrier sizes/spline count? I have a 10-bolt in my 88 and it has a 7 5/8 in. carrier and ive seen some confusing info as to the actual meaning of GM's claim that my "slightly larger" gear carrier is somehow different from and better than the earlier 7 1/2 in. ones. Did the carriers actually physically change when they went form the 7 1/2 to the 7 5/8 in carrier? Is it just the same as the 7 1/2 in carier and GM just changed the designation of the carrier just to confuse us? As for the spline counts, did they change to the 28 spline axles when they changed over to the "7 5/8" carrier or did they make the change from the 26 to the 28 spline axles independantly of the redesignation of the gear carrier from the 7 1/2 to the 7 5/8 in.? There seems to be some ambiguity as to the time frame of these changes and whether or not they actually changed the gear carriers.

 

The carriers are the same size since the gears are interchangable on the same carrier. There are differences in each carrier. You can't just put 28 spline side gears in a 26 spline carrier. The axles won't fit through the casting holes.

GM upgraded from 7 1/2" to 7 5/8" around 1986. They didn't upgrade from 26 spline to 28 spline until 1990 however there may be a few late 1989 cars with 28 spline axles.