Trans pump feeds the front pump. It also provides pressure for Reverser, HI-LO, and Independent PTO clutch & brake if you have any of those options.
Sounds like something went thru the pump gears to lock it up and break gear teeth.
The transmission pump is fed from the sump. The transmission reservoir screen is it's only inlet "filter". Output first goes to the transmission filter, then to the front pump. The transmission oil filter has a relief valve that dumps back to sump if the filter is clogged. There is a "surge relief" valve (if without reverser) between the trans filter and the front pump. It opens if the pressure from the transmission pump exceeds 100-140psi and dumps to sump.
Also as stated earlier, the transmission pump supplies the Reverser, HI-LO, and Ind PTO clutch & brake if so equipped.