I am Looking at a F-350 Pickup with a Powerstroke Diesel when I took it for a test drive it ran fine I did notice that when I took my foot of the eccelator that the motor seemed to brake as the truck slowed down not in the sence of miss fire but a actual gear reduction it is a aotomatic with overdrive.

 

Might be a little speculation here, but the diesel has enough torque to allow for a much tighter torque converter. If you are coming off of higer RPM's like over 1800 and get off throttle I could see where you would experience brake torque issues because of this. Of course I am only speculating, but it make the most sense to me.