-What axles do I have in my truck?
'85-'87 Isuzu 8 bolt front/ Isuzu 10 bolt rear
'88-'00 (non TOD) Isuzu 10 bolt front/ Isuzu 12 bolt rear
All TOD models Modified Isuzu 10 bolt front/ Modified Isuzu 12 bolt rear
Some Troopers where equipped with a limited slip rear differential. This is
designated by the code G80 on the option ID plate in the engine compartment.
-What are my gear ratios, what is my crawl ratio?
Some '88-'91 Troopers where equipped with the factory "wide tire package"
that included 4.77:1 axle gears. This would bring the crawl ratio to 41.0:1
with a manual transmission. This is designated by the code S2J on the option
ID plate in the engine compartment.
http://totalescape.com/Amigo/text/trooperFAQ.html