GUIDE: EASY AXLE IDENTIFICATION 7.5 VS 8.5
----7.5/7.625 These are easily identifiable b 1. sharp "teeth" on the bottom of the center housing 2. oval shaped diff covers(bolt spacing of 3.75") and oval center castings with flats on the side 3. An unbulged, uniform axle tube diameter the entire length of the axle. ----8.625(also called 8.5) These are easily identifiable by....having 1. Big square teeth on the bottom of the center housing. 2. bulged axle tubes near the center housing that taper down 3. nearly completely round diff covers(bolt spacing of ~3.25")
4. round center castings, --The "teeth" alone make the axle ring gear size easy to identify even when you see s10s from the rear in traffic going down the road. all of these are 1998+
APPLICATIONS
----7.5/7.625 These are in ~95-98% of s10s on the road. --These come in ratios of....GT4-3.73 gear ratio, GT5-4.10 gear ratio, GU4-3.08 gear ratio, GU6-3.42 gear ratio --These are available in widths WMS to WMS 54.5" wide and 58.5" with disks and drums. ----8.625(8.5) These are 1998+ only will basically ONLY come factory in a v6 truck, and in all zr2 trucks. Very few 2.2 trucks came factory with one, but SOME DID. 4x4s will have them a little more commonly as well. --They also come mostly in 4.3/5spd trucks but DO NOT assume this to be 100% true, verify yourself by using our pictures here! ive checked 11 trucks myself that were L35 4.3/m50 5 speed and NONE had an 8.5 except a zr2 and one 4x4 blazer but it was bent to shit. Canada trucks have them more often too --These come in the same widths WMS to WMS as the 7.5s, and also the ZR2s are 62.5" wide. More commonly found with disks it seems but plenty of 8.5 drum rears out there too
AXLE SPLINE COUNTS
----7.5/7.625 7.5 rears in 4 cyl trucks had 26 splines till 1993, and 4.3 trucks had 26 splines till 1989ish, after this they all went to 28 spline
----8.625(8.5) 8.625 rears will all have 30 spline rear axles in s10s and are 98+ only
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