Here's why you need to determine the specifics:
* Gear Ratio: The gear ratio in your rear differential will affect the type of oil needed. Different gear ratios require different viscosities.
* Limited Slip Differential (LSD): Does your truck have a limited slip differential? If so, it requires special oil that contains friction modifiers.
* Operating Conditions: Where you live (climate) and how you drive your truck (heavy towing, off-roading) will influence the best oil choice.
Here's how to find the information:
1. Look in your Owner's Manual: If you have the original manual, it will provide the recommended oil specifications.
2. Check the Differential Tag: Look on the differential housing itself for a tag that lists the gear ratio and any other relevant information.
3. Consult a Reputable Parts Store: A local auto parts store can help you determine the correct oil based on your truck's specifications.
4. Search Online: Websites like FordParts.com or a Ford-specific forum may have helpful information about your specific model year.
General Advice:
* Most rear differentials in older F-150s use GL-5 gear oil.
* Be sure to use the correct viscosity for your gear ratio.
* If you have a limited slip differential, use GL-5 gear oil with friction modifiers specifically designed for LSDs.
Remember: Always refer to your owner's manual or consult a professional for the most accurate recommendations for your 1980 F-150.
