I have a loud knock when in gear and the truck is cold. It does not knock at idle. When giving it throttle in gear it sounds like a loud rod knock. It is only when the truck is cold. As soon as it warms up for 2-3 min. the knock goes away. My buddy who has been a dodge tech for 20 years thinks it is the flex plate. That partially makes sense to me because cracked flex plates typically sound like a rod knock but I don't understand why it only does it when cold.

Anybody else had these symptoms? Any ideas?

 

I vote flexplate. In my experience, when a rod starts knocking it doesn't go away. How's your oil pressure?

 

I know it's not the motor...everything is good there. It just sounds similar to that. Will a flex plate noise go away after it warms up for a few minutes?

 

i'm interested in this one as well. i have a faint knock at idle that goes away with increased rpm. been there since i bought the truck 2 years ago. comes from the bottom end, more toward the rear than the front. i replaced oil pump - main bearings seemed fine. rod bearings were tight. i didn't even look at the flex plate. damn !

if its the flex plate, what causes it to knock ?
will it get worse ?
whats the worst thing that could happen ?

 

A crack in the flex plate causes it to knock and it will get worse over time. Eventually, the crack will continue and the plate will break free from the mounting bolts which means no power to the drive shaft.

 

How does it cause it to knock?

 

The cracked plate will jiggle causing a rhythmic sound similar to rod knock but somewhat higher pitched. A loose bolt to the TC is enough to crack it and it only gets worse.

edit: BTW ... if it goes away after warmup, I doubt if it's the flexplate. I suspect an active component ... TC or front pump.

 

any pics of the location?