Combines Which was first Gleaner that could have RWAIJ

Any of the hydros could have RWA, the later models with external charge pumps were better. Gilcrest and MudHog both retrofitted early hydro models. I once saw a 4420 non hydro Deere with a RWA. Ask the owner how it worked - I meant as to the mechanics - he answered "not very well..."

Which brings up an interesting point; how can a combine with gear_variable speed drive power a RWA unitIJ

add a pump, add a flow valve, make it not too strong....

I had a neighbor with a 4400 JD that had a Mud Hog RWA on it.He put it on in 1981 to mud out 1200 acres of wheat and then got to mud out all 1200 acres of DC beans behind the wheat that fall. I never really did look the combine over or ride with him to see how it worked with a variable speed drive.He had big terra tires up front and added a turbo for some extra power and it ran good in the mud. The first factory RWA combine I ever saw around here was a 7700 JD in the mid 70's.There were alot of l2 Gleaner RWA combines in our area.