I have a 1998 Ranger that has almost 300,000mls on her and has run like a top til yesterday, coming home from work, going up a hill and she starts making this whining noise and the oil guage is jumping up and down......anyone that can help would be greatly appreciated. My first thought was the oil pump???

 

Could you give a little more info plz? Whats the engine size? It could be nothing more than the oil piclup being restricted. I have recently done this for 2.3l ford ranger pickup with fewer miles. It was pretty easy to determine this after I used a mechanical gauge and installed in port where the oil pressure gauge was to verify the oil pressure was lacking and it was not just a electrical sensor problem. This job requires the removal of transmission and still fighting the oil pan off of vehicle. I sure hope you don't have a 4x4