2014 Cascaida Thud Knock when coasting -10 mph

Need help...truck makes a thud popping noise. It sounds like coming from under the transmission but I can feel it in steering and not in gear stick. Only does it going straight under weight and under 10 mph. Took into dealer and they couldn't find problem. Steering gear box is leaking oil on engine side but I cant find any I other issues. Has any one dealt with this issue? Thank you!

 

Thank you...I will look into that. The dealer said the road tested it but it wasnt under a load and you get a lot of undetectable problems when pulling 40k vs bobtail.

 

Yes only under heavy load. I feels like its coming from driverside axle. The shock is busted on that side. I'm going to replace tomorrow.

 

Taking to the shop as my dash also went orange. Gotta love these trucks. Thx for the information!