* TH350 (3-speed automatic): Use Dexron III or a compatible ATF fluid. Dexron VI is generally backward compatible but check your owner's manual to be certain.
* TH400 (3-speed automatic): Use Type F automatic transmission fluid. Some people use Dexron III as a substitute, but Type F is recommended.
* SM465 (4-speed manual): This transmission uses gear oil, typically a 80W-90 GL-1 or GL-3 rated gear oil. Consult your owner's manual for the specific recommendation.
To determine which transmission you have:
* Check under the truck: Look at the transmission case for identifying numbers. These numbers can be used to identify the exact transmission type.
* Check your owner's manual: If you have the original owner's manual, it will specify the correct transmission and fluid type.
Important Note: Always check the condition of your transmission fluid regularly and change it according to the manufacturer's recommendations. Using the wrong fluid can severely damage your transmission.
