In the earlier days(60's, early 70's) of GM, the manuals said to use ATF for power steering units. Nowadays, its Power Steering Fluid only. Anyone know why the change occurred and what happens if you use ATF in place of Power Steering Fluid?

The only thing that changed was the ATF types and grades. GM still say's you can use it. They just dont say it with there cars anymore. I am in full time school for Mercury & Mercruiser boat company. They are all GM aswell as GM's testing ground for motors. With the boats that have powersteering GM still says ATF is just fine in place of PS fluid.

Thanks for the info, CarguyinOK. I suspected it. They just want us to buy another kind of fluid.