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Is there a simple way to determine the differential type without damaging the underbody?

Crawl under the rear of the truck and look at the diff. It should have one breather hose and possibly two little wires if the truck has ABS. If the truck has a locker, there should be some other air/vacuum line stickin' out of there somewhere.

'06 Dakota QC 4.7 6sp 4x4
'88 Mighty Max
'77 KZ1000 fun old bike