Tranny fluid should come up pretty easily with kitty litter or just rinsing. The stuff is the most caustic stuff in a car. If you ever get your hands really greasy or covered in a poly paint you can use tranny fluid to get the big stuff off your hand and out from under your nails. At first it looks all messy, but after scrubbing your hands together then rinsing it off you would be surprised at how clean your hands are. Now I don't recommend doing this every day as the stuff is toxic and excessive exposure will get you sick! If where it got on the concrete looks discolored the issue probably isn't tranny fluid stains as much as the tranny fluid removed any color dye in the concrete. Uncolored concrete is grey, but most people like a tan drive which requires a dye being used in the concrete mix. If this is the case you have two choices. Use tranny fluid to strip all the color out of the surface of the concrete which will probably get you in trouble with the EPA and every tree hugger within 1000 miles or paint the driveway with concrete paint, but even that requires you to wash your drive with a muric acid mixture to make sure it is absolutely clean and the paint will stick.
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