OK last week I'm driving my Stang (auto trans) and in overdrive when there's minimum load on the motor around 40 MPH I feel what I can describe as a surging in the car. Its almost like the torque converter is letting go then locking up and back and forth it continues till I give it a little gas. I took it out of overdrive and it will do the same thing except not as violent. So yesterday I changed out the fluid, filter, and did the jmod. It didn't help at all. The fluid looked great and not burnt. I'm pretty sure its not a misfire and the car is not throwing any codes. Any suggestions?

 

Maybe the fuel filter needs to be changed?

 

I really don't think its the engine