I get a clunk noise and feel it under my feet when im going around 40 mph and slightly press the gas to go up a few mph. only does it around 40 mph. It only clucks when 'feathering' the gas around 40 mph. Ideas? Thanks

 

low grade misfire, how many miles and have the plugs been changed? If they have been changed, its probably a COP. If not, change the plugs. My truck does the same, jump/clunks in 4th gear O/D around 40mph. I have 120k miles with stock plugs.

 

145K miles, plugs changed at 96K. thanks for reply.