Yes, you can. You can use ATF or automatic transmission fluid in your power steering pump as a substitute for power steering fluid when you're in a bind. Both your ATF and power steering fluid are hydraulic fluids and your power steering system is a hydraulic system like your transmission system.
ATF benefits you by having detergents within its formula that help in keeping your system clean. Many cars and trucks actually require ATF in their power steering pump. Read your vehicle's manual to see if this is the case for your make and model of automobile.
Proper fluid that's recommended by the manufacturer isn't all that expensive and you can buy recommended fluid just as easily as ATF. But in a pinch, you can substitute it for ATF.
Several Points to Take Note Of
- Are There Savings in Using ATF on Your Power Steering Pump? No. Sometimes, it might be cheaper to get the recommended fluid that using your ATF on your power steering pump. There are no savings to be had from using ATF on your pump at all, in fact. Some mechanics use ATF instead of power steering fluid for convenience because they don't want to keep a bunch of different fluids on their shelf since the compatibility of both of the fluids has been established.
- Losing Fluid and Using ATF to Fill in That Loss: If you're losing power steering fluid you can use ATF to fill it up. However, that's just you addressing a symptom of the problem, not the cause. It's better to fix the problem by replacing the worn seals instead of filling up fluid you'll eventually lose over time as your pump starts to burn, melt, and get damaged by always being empty. Power steering pumps should be fixed if they're leaking.
- Power Steering Fluid versus ATF: Is power steering fluid exactly the same as transmission fluid? No, but they're the same type of fluid. They're both hydraulic fluids. Physically, ATF is red-colored that has a sweet smell to it. Meanwhile, power steering fluid is pinkish, amber, or clear and smells like burnt marshmallow instead. ATF, however, contains friction modifiers and detergents to clean out the automatic transmission's dirt and grease away yet damage the hydraulic valves of the steering rack and pump.
- Can You Put Power Steering Fluid into Your Automatic Transmission? Curiously enough, yes and no. Yes because power steering fluid, like ATF, is a hydraulic fluid type so it's not like you're pumping your automatic transmission with alcohol or gasoline or something horrendous. No because ATF is superior to power steering fluid when it comes to its additives. Power steering fluid lacks detergents that filter dirt and grease away. It also doesn't have friction modifiers needed to keep excessive heat buildup at bay.