Updated

Martin Truex Jr. will have a new crew chief beginning this weekend at Pocono Raceway.

Lead engineer Chad Johnston is replacing Pat Tryson as crew chief of Truex's No. 56 Toyota.

Tryson has been reassigned to another position at Michael Waltrip Racing. He left Penske Racing at the end of the 2009 season to join Truex at MWR, and he's got one year remaining on his contract.

Truex has had a rough start to the season. He's 21st in the Sprint Cup standings with just three top-10 finishes.

He angrily fired his crew over his team radio following a botched final pit stop at Richmond, and that led to changes on his over-the-wall team the next week.