This is a common problem in almost all the allis tractors with the hydraulic power director. The bad news is that you are needing the power director rebuilt. This requires a rear split of the tractor. The clutches and seals are not terribly expensive for these but if any of the hard parts are damaged they tend to be VERY expensive. I strongly suggest not operating the tractor at all other than to load on a trailer until this fixed. Every time you run it till it stops is running this unit out of oil and damaging the power director further.
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You can place pipe fittings in place of the drain plugs(front and rear) and connect them with some plastic hose. then refill the system. I would use a minimum 1" hose to connect the two. This should get you by for quite a while until the power director clutches completely fail(may last a long time). Keep in mind that this hose will be vulnerable to being caught on debris underneath the tractor and will cause you to loose all your hydraulic oil rapidly, but operationally it should work fine.