from what ive learned, the vast majority of the crappie empty out of the main lake in late fall and winter on Granger.
this tends to be common on primarily shallow lakes such as Granger.
maybe try some night fishing in the river . I recall the locals used to go build a fire on the bank for some warmth and light and do pretty good fishing minnows under lighted floats.. be patient, because in river systems the crappie will move back and forth, chasing the shad around all night.. crappie can get on patterns where they feed heavily at night, and then get tight up to cover during daylight hours to digest thier food, and just wont bite.
Maybe bring a castnet with you and try to catch some shad
try to find a place in the river that makes a hard bend, and has a fairly steep drop on the outside of the bend.
pay close attention to the bird locations. if you find gulls, terns, cormorants set up at the mouth of the river, that would be a great place to start.
double rigs set at different depths will help you zero in in on them.

A good friend has been catching em. A limit every time, no b\p or stumps. Just go looking for em open water and keep moving!!