Gotta check all the normal things:
Definitely change the fluid and filter, making sure to use the correct filter
Look at the linkage and make sure moving the lever on the dash moves the trunion on the hydro.
Also inspect the trunion and make sure the slot where the springs ride isn't all worn out
I don't know the driveshaft setup on a 782 but maybe you sheared a pin in the driveshaft and the pump isn't even spinning?
Not sure if there's even a pin to shear or not though
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'70 107 with k301 engine swap
'71 106 with 38" deck
'70 147
R with factory replacement k321, 42" deck
'61 Original with 38" timed deck
'63 70 "pinkie"
1863 with 54" deck
'46 Farmall H, '50 Farmall Cub
105 x2 (parts)