GM made two housings that came in these trucks, the 7.5/ 7.625 and the 8.5, both of which are ten bolts. The 7.5 has more of a squared of shape to the cover and straight axles tubes that measure 2 3/4" whereas the 8.5 uses a round cover and the axle tubes step down from 3" to 2 3/4" near the leaf pads. This photo shows the 7.5 on top and the 8.5 on the bottom.
2 wheel drive width from WMS to WMS is 54.5 inches
4 wheel drive width from WMS to WMS is 59-60 (depending who measures it) inches
S10 Rear end Ring Gear and Axle Sizes:
1983 to 1992 7.5" ring gear 26 spline axles
Available from 1988+ 7.625" ring gear 28 spline axles
Available from 1995 and up, 8.5" ring gear 30 spline axles, standard for 98+ ZR2's with rear discs
These are some of the axle RPO codes and should be the same for all GMs with either of these axles.
G80= locking differential
Here is a Ford ID tag that should be on the axle however many scrap yards remove these (some people will swap a locker tag with open tag to save money hint, hint)
Rear axle codes can be found on a label attached to the left drivers side door lock post. The code appears as a number or letter/number combination in the 'Axle' column of the label. The axle can also be identified by the tag on the axle differential cover bolt. See the diagram above to learn how to read the tag.
All disk brake Explorer rear ends had 31 spline axles however there were a few drum brake rears that were 28 spline. Disc brakes was 95+
All Ranger other the the FX4 20002 and 2003 Lever II trim had 28 spline axles
Here's all the specs, measurements, and misc crap about the Explorer 8.8 you'll ever want to know.
Ford 8.8 specs:
Weight (complete assembly w/ brakes etc.): 174 lb.
Axle shaft strength: 6,500 (lb. ft.)
Drivers side Ford brake hose #:F5TZ-2282-A
Passenger side brake hose #: XL2Z-2282-AA
Bolt size (U-joint flange to yoke) is: 12 x 1.75 x 30 mm
Driveshaft Flange: Spicer Part Number 2-2-1379
O.D. of tubes: 3.250".
Tube thickness: .250" (some are .188”!)
Ring gear diameter: 8.800".
Ring gear bolts: 7/16" dia. (qty. 10).
Pinion diameter/splines: 1.625 / 30.
Axle shaft/splines: 1.320 / 31.
Rotor thickness (where it mounts to axle is .250").
Overall width 59.625". I have come up measurements online that say up to an inch wider, check yourself to be sure.
Hole diameter for ABS sensor in top of housing: .811".
Centerline of housing to C/L of pinion difference is 3.875" toward the P/S.
Explorer disks are non vented and measure 11 1/4" and are 5/8" thick.
8.8 to 7.5 comparison pics. Jason sent me these in an email, thanks Jason.