it's like buying any other vehicle.
the simple stuff :
check fluids and their condition - they can tell you alot about the truck without even driving it.
check for loose parts/ jimmy-rigged fixes and note them - some repairs are not always done right obviously.
if you need tires, take that into account and price them. standard sizes for these trucks are 195/75-14
drive it - make note of any noises/ quirks that are present or that affect the truck's driveability.
check electrical harness condition - a quick visual inspection of the harness itself can tell you whether splicing or modification has taken place.
lastly, just take a look at overall condition. look for the obvious stuff and keep it in mind when making offers.
if you can, or have access to, take the truck to a mechanic to have him give it a look-over and see if there are any underlying problems.
also, this forum provides a wealth of information, so if you need to repair, say....a head gasket, we can help you fix it with procedures and information.
if you find some problems or have concerns about this truck, just ask us here and we will do the best we can to answer you
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To the Oquirr hills for awesome thrills! Go-go 4wd, Activate!