well I think you may have had a 3/8 socket on the serpintine belt..the one that drives the alt..power steering..etc. the one im talking about is BEHIND the plastic cover that houses the timing belt. It is the idler / tensioner pully. it is held in place via a 13mm bolt. and then a larger one with a spring on it...i might have a picture if it would help.

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1996 ford ranger 2.3l reg cab 2wd auto.