Here's why you shouldn't use automatic transmission fluid (ATF):
* Different Lubrication Properties: MTF is specifically designed for manual transmissions with its thicker viscosity and higher friction coefficients. This helps with gear engagement and clutch operation. ATF is thinner and designed for the torque converter and hydraulic systems in automatics.
* Damage Potential: Using ATF in a manual transmission can lead to slippage, premature wear, and even damage to the transmission.
Key points to consider:
* Specific Fluid Recommendations: Consult your owner's manual or a Ford dealer to get the exact fluid recommendations for your specific 1991 F-150. They might specify a particular type or brand of MTF.
* Synthetic vs. Conventional: Synthetic MTFs generally offer better protection and performance, especially in extreme conditions. However, conventional MTF is still a suitable option.
* Fluid Change Intervals: Check your owner's manual for recommended service intervals for your transmission.
Never use ATF in a manual transmission, and always refer to your owner's manual for the most accurate fluid recommendations.
