Joe, I don't have a book on the 977H, but all of the D333's I have books for show a cast aluminum suction bell with a screen assembly inside and a cover over that which has the hole in the bottom for the pump to suck up oil through. On those, the screen assembly is a separate part bolted between the bell and the cover with gaskets.
If you do have one like that, be very careful of the bell, they are easy to break off the flange where they bolt to the pump.
Which oil pump are you referring to? Powershift hydraulic system, loader or main engine?
It's for the main engine. And yes it has a bell with a screen in it, but it also has the tube on the other side of the pump that goes along the pan plate that picks up oil on the back of the engine.
OK, now I see it. The 58B1 - 58B2417 parts book has the front pickup tube part number 1M2837 and shows a 5F1678 "seal" o-ring at the pump end where the tube plugs into the pump.
I believe I would get some good screen and figure a way to fasten it on the tube. I think McMaster Carr has some brass screen that you could use if you can't find something suitable locally.
That back tube is just a scavange pipe and is part of the pump but not the pressure side of the pump but just picks up oil that would collect when your more or less on a grade and that side of the pump just dumps the oil back in the main (deep) sump for the main pump to pick up for lube to the whole engine so the scavange pump doesn,t lube the engine. This scavange side won,t let the main sump of the pump loose oil so there isn,t enough to pump pressure.