To find the correct gear oil, you MUST consult your owner's manual. This manual will specify the correct type and amount of gear oil for your specific truck's rear axle.
Alternatively, you can:
* Check the sticker on the differential: Often, there's a sticker on the differential cover indicating the recommended gear oil type and capacity.
* Use your VIN number: A parts store or Dodge dealership can use your VIN to determine the correct gear oil for your truck.
Without this information, any recommendation I give could be incorrect and potentially damage your rear axle. Do not attempt to guess. Getting the wrong gear oil can lead to premature wear and failure of your rear differential.