Just bought another 4runner off craigslist, friday night. 2wheel drive, auto, 3.0 v6, grabbed it for $500, engine runs great, clean inside, some body rust over rear wells, heres my issue.. Drove it home 45 miles, ran great except a whirring noise from the rear at highway speeds, let off gas and it goes away, so its not the tires, does NOT shift hard or anything. Got home and parked it, tried to start it again 30 minutes later and nothing, no click of bad starter, nothing, dash lights and headlights work,, hmmm.. try again an hour later and it starts right up.. Take it the next morning get the oil changed and the fluids checked, everything is fine... battery tests at 10, heres the question I guess,, Is there anyway that a bad alternator could be causing the noise from the rear end,, has anyone ever heard of this?? thanks guys

 

battery tests at 10 what? volts? battery should be 12+ volts.

rear end noise has nothing to do with the battery / alternator. May be pinion or u-joints making noise in the rear.