I've been enjoying my 3.4 for the last few months and made a number of runs up to the hills for the ski season. Haven't had any issues except for the exhaust falling apart because cheap bolts from the exhaust shop.
Anyway, about a week ago I started hearing a little ticking/knocking sound from the under carriage when I was at stop lights. A couple days later the noise got louder but when I put the truck in neutral it stopped. I thought it was the transmission but I'm not so sure now. This week the knocking noise has changed to more of a rattle and it only occurs between 1000 and 1500 RPM. I crawled under the truck while in drive with the e-brake on, and used the old screw drive to your ear trick. As best as I can tell it is either the lower part of the engine, the torque converter, or (cross my fingers) the "extra" leg of the oil pick up that I couldn't bolt the block. It sounds like a loose heat shield but I couldn't find any that were loose. The performance isn't affected at all but damn if it isn't driving me crazy! Any ideas???

 

Cracked flex plate. Remove the sheild where the torque converter bolts are and look up in there. You may want to have someone turn it over by hand.

 

Do you think the flex plate is loose from the torque converter? Didn't think of that.

 

No, I have had a few come into the dealership that was cracked around the crankshaft bolts.

 

Is the crack visible from the bottom or will I only see it if the motor is turning over?