The duo have committed to the Borough Park club until the summer of 2023.
It follows the impressive work done by Grainger and Rudd over the last two campaigns.
They were denied promotion from the Northern Premier League North West Division last season by the curtailment of the campaign after the Covid-19 outbreak.
Reds were top of the table then, and sat third when the current campaign came to a halt.
Former Carlisle United captain Grainger, 34, said he was "over the moon" to have extended his stay with the west Cumbrian club.
"We are excited in the direction the club wants to go, and can’t wait for next season whatever challenges lay ahead," said the man from Eamont Bridge near Penrith, who took charge in 2019 shortly after ending his playing career.