2014 Cascaida Thud Knock when coasting -10 mph

Was it involved in an accident or something. Just asking because of the broken shock. That doesnt help at least with your problem. I suspect you are going to have to dig deeper to find the root cause. This due to the fact your dash(assuming you mean check engine light) is lit up all of a sudden. Good luck man and dont be afraid to tell your mechanic if you know for a fact hes doing something wrong. I know of very few tests on a truck that arent under load.

 

Thud knock when coasting could be a differential.....especially if it has any growl or noise to it

 

Have someone and or people walk next to it in the parking lot. If you ask the right way most will get out of the drivers room.

 

that noise is coming from fifth wheel. The rail of 5th wheel..