welcome to the bolt Lonnie - tell us more about the model designation of this big rig - the "Spartan" just means it's in the 21-26,000 GVW range, and a plain "100" is a light duty GMC model - I think yours would be in the 10,000 series, like 10100 maybe, which is a 2-1/2T, and woulda had 22.5 wheels originally
if chev rear it'd be 6.40:1/8.72:1 and if an eaton it'd be 6.50:1 and either 9.04 or 8.87:1 - model and ratio should be stamped on top carrier
Kool covered the other issues, but the shop manual covers the big bolts too, so it'd be a good thing to have for fix-ups - I'll just add we sure like pictures around here!
need some more big bolts in the gallery, especially Task Force series!
Bill
