OTC1794A Transmission Jack

What does the air/hydraulic jack mean on the OTC 1794A transmission jack? I have seen transmission jacks that are hydraulic or air but not both. Can you explain this a little better?

Air/hydraulic means is that the primary or first stage of lifting is done using an air jack that is powered by your shop air. The first stage is simply to lift the transmission jack into position before the transmission is actually lefted up. Once the jack is in position, you pump the hydraulic jack to lift the load . This unit also has brakes on 2 of the wheels. This is a nice added safety feature that allows to brake the jack so it won't roll across the shop.