Transmission Fluid - C4

Slipping can be caused by a few different things. Low fluid level, broken down fluid (gotten too hot), wrong fluid, your clutches can get loose over time, or you have vacuum issues.

Always run Type F in a C4 or C6 transmission. Type F has a zinc additive that is critical to prevent wear, and for the transmission to shift properly.

The vacuum issue can be tricky. You can modify the shift points by adjusting the modulator on the back of the trans (passenger side, near the pan) It requires a slotted small screwdriver. Turning the screw in, will make your shift points a little bit later. Too much vacuum will cause weird stuff like flares between gears, and slippage off the line. You'll have to do some research on the proper vacuum, I can't remember off the top of my head how many inches are 'healthy'.

If you haven't done it recently, service your transmission, or have it done. Change that fluid if it smells even a little bit burnt or hot. Get a cooler, it makes a world of difference in promoting the life of your transmission, it's #1 enemy is heat.

"ATF" is an abbreviation for Automatic Transmission Fluid -- a generic term. The most commonly-used ATF is Dexron/Mercon. Don't use it in your Ford! Only use type F. If you have a mixture of fluids in there, now's the time to do a fluid change!