Engine/Transmission (1998.5 - 2002) Weird problem after start up!

[Mbranson]

I hope someone can help me,the last two times I started my truck a few seconds after it starts I hear and feel a slight bang in the floor board then it does it no more. It runs fine, shifts fine, no vibrations, it runs no different than before the problem started,any help would be appreciated. 01. 5 quad cab 4x4 47re auto 2500 5. 9 74. 000 miles

 

[Missouri Mule]

Possible broken motor/trans mount, but then again I could be way out in left field.

 

[hcole]

Sounds like it could be loose starter bolts.