I have a 09 screw w/ 4.6. Whenever I accelerate I hear a loud metallic rattle coming from the front of the truck. It sound like it's coming from underneath the truck on the drivers side. There's no loss of power when this happens and I can't replicate the sound while in neutral. At first I thought it was knocking/pinging but since there's no loss of power I don't think that's it. Anyone have any ideas of what this could be?

 

Might be torque converter. Does it happen under light acceleration like lugging the motor? Does it go away when you accelerate or let off?

 

Kind of. It always starts at a low load, and then if I accelerate harder the rattle will taper off.

 

Also if I let off as soon as it starts the rattle will go away

 

I'm betting torque converter.

 

Mine is making a strange noise too - might be similar or the same.....?

https://www.f150forum.com/f70/5-0-sp...8/#post3408780