They enter a loom just behind the front right fender and head into the engine bay. They come up and terminate on a vac block dead center at the top of the firewall.
that line is the vacuum source from the engine that engages the shifting fork in your front axle thus engaging your 4 wheel drive. There should be this vac line leading to the front axle and eventually it should be bundled with another vac line heading back under the body to the transfer case.
check and make sure all lines are secure, otherwise you can install a posilok system or do a bypass here is the posi lok link:
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