Hello Everybody!! i have an 05 lly 4 door short bed 175000 km on it and its amazing. i had this tick that turned into a very loud knock. it only does it from idle to 1500 rpm and when the engine is warm. i brought it to a very reputable diesel shop and they thought injectors or lifters, they pulled the motor apart and found zero issues they said it was perfect in there. they did some digging and found a bulletin from gm saying these trucks can get a knock from the coolant running through the block gm says it isnt a problem with reliability or performance but it is so dam annoying lol does anybody hear have any other possible ideas it could be? they only checked for lifters and injectors( and whatever else you can see in the motor by getting to the lifters) Thanks again!!