Rpm issues
 

Hey yall! New here and got a question ! My 05 2500 5.9 6 speed is having rpm issues . Idle is at 400 when I am crusing at 75 its almost red lined ! Doesn't happen when first started only after driving about 5 minutes then it starts . Attaching pics of first start and then 5 minutes later at crusing speed . Any help is greatly appreciated. https://cimg2.ibsrv.net/gimg/www.die...3f80431471.jpg
https://cimg3.ibsrv.net/gimg/www.die...494054d342.jpg