I know some engines have harmonic balancers on the lower pulley..not sure about the Ranger engine but on some Ford 4.0's, in Mustangs, there was a recall on this balancer.

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2008 Ranger XLT 4X4 V6 4.0 Torch Red
Bought September 29, 2011 mileage 13,800 2nd owner

Mods:
Retractable Truck Stake Pocket Anchors...installed 10-5-11, AVS Window Vent Visors, 10-6-11,Tonneau Cover, 10-15-11, Alarm/remote start and locks, 10-25-11, Bed Lights 11-13-11, front mud flaps 11-20-11, deer whistles 11-25-11, brake lite Ford emblem 12-7-11