04 silverado skip shift?

I recently purchased an 04 silverado single cab 4.8 w/ a 5 spd. Has anyone heard of a skip shift in this truck?. Under heavy acceleration, redline, it will not let me shift from second to third. The only way to get to third is to go straight to fourth then back to third which costs me a sec or two. (thats how i lost to a mustang gt) :mad: If anyone knows how to bypass please let me know.