Isx 400 hesitating

[Derekthetusken]

(04-08-2019 )Rawze Wrote:  What year, make, model engine, truck?

some history?

does it sound kind of like a screech? - (like someone letting the air out of a metal balloon)?

or does it sound like a high-speed smooth sounding whine?

BTW: Mistake #1,.. taking it to the stealershit is worst place a person can go these days.

2009 kw T660 isx400st
I’ve changed egr doc dpf turbo and the part that goes beneath the turbo changed the computer the sound is the turbo I guess like the high speed smooth sound. So when I shift from like 6th to 7th which goes from approximately 1700 to 1200 rpms it hesitates while that whistling is happening and it slowly goes away than accelerates like normal. Also this doesn’t happen all the time now that the dpf was replaced. Kenworth dealership said all systems working correctly after dpf was changed. I was trying to get a extended warranty so they have to do a major inspection on the truck. Thanks again for the help