Flex plate

[Spindrift]

Has anyone lost a flex plate? One minute I start the truck and it runs fine. About an hour later I go out to the truck to run an errand, start the truck and all of a sudden I hear a racket that makes my heart stop. Definitely sounds rotational and as near as I can tell it's coming from the bottom end at the rear of the engine. Sounds like a rod knock. Checked oil pressure at idle and I'm at 50psi...rev the engine a little and pressure jumps to 75psi. So I really doubt I've lost a bearing or I'd see a drop in oil pressure from normal. I'm thinking/hoping I have a transmission issue.

Truck has 118K on it. Nothing has been done to the trans.

 

[Gary]

Maybe A/C compressor clutch bearing, I've seen a few fail.

 

[Mdub707]

I lost a flex plate driving down the road. Completely separated from the hub. It was making the truck vibrate something awful, but the motor ran very smooth. I shut the truck off and went to re-start and the starter just spun like crazy as it wasn't catching on the teeth of the flex plate anymore. Should be able to remove the cover for the torque cover bolts and put a bar in there and try to turn the flex plate I'd think.

What other mods on the truck? Does it actually start up and run? Have you tried driving it? Tried reading any codes?

 

[Big Angry Hillbilly]

I'm pretty sure mine is cracked on my 6.4.