Possibly a hydraulic valve lifter may be sticking or part of the exhaust system is loose. If you can do without the truck for a day, take it to the registered dealer and ask them to start it when it's cold.
Thankyou,, i will do that.
it might be a loose heat shield around the exhaust ! if it was the engine then it should knock sitting and idling ! also have the transmission mount checked out, it might be busted !
ask mechanic!
and only knocks when it is in drive,,,,doesnt knock in any other gear
