I have a 2000 lariat with a 5.4 and an automatic. I'm a good mechanic, but was curious if anyone had an issue like this. I have a steady knock from the rear of the engine, or the front of the tranny. When i rev the motor it almost goes away. When the gas is let up the knock gets louder and more frequent, almost to a rattle. When I hold the brake and apply the gas it doesn't get louder like a rod or main bearing would. It does follow engine rpm with frequency, but not loudness. It is worse at engine deceleration. The engine runs great, with great oil pressure, and no shavings in the oil. It started after passing a semi on a 2 lane road, under heavy acceleration. I'm thinking flywheel or torque converter, but I couldn't see any cracks in the flywheel with the inspection plate removed. It also does make any noise for the first 30 sec or so at start up. It starts after I rev it up a couple times. This thing is a pain to diagnose, please help.

 

I've seen exhaust leaks that sound like what you describe. Try inspecting it in the dark so you can see the exhaust leak.

 

Some of the reasons for noise are worn main thrust bearing on the crank caused by a bad converter or front trans pump putting to much forward pressure on the crank , the flywheel has a crack, the converter internal turbine vanes, ballooned converter has caused the torrington bearings to break up.
Stethoscope should be able to localize the noise area.
Check the crank end play.
Check for metal bits on the magnet in the trans pan.

 

did you check all the torque converter flywheel bolts?

I like to look for the small obvious things first.

on some engines the heads of the bolts can actually rub if they back out

 

thanks guys, those are educated replies and confirmed my thoughts. I need to pull the motor from the tranny and the oil pan to be sure. I hate thimgs like this that have more than possibilities, all of which require a weekend full of fixing a truck. Why can't it more simple with better results, like bolting on a Kenne Bell.

 

I am kinda having a similar problem, but in reverse, with my 1997 4x4 4.6 If i really get into the throttle and it downshifts and runs the RPMs to about 4000 or 4500 i get a strange popping noise from approx the same area. The truck is still pulling good and not shaking or anything, just this noise. If i put the truck in park and just rev the engine and hold itat 4500 it sounds like a fine motor so I know its not the engine....at least im fairly certain. Fluids are good in everything so Im kinda stumped........any ideas?

 

My case seems much different but the guys here seem to know there stuff. I have a 05 Supercab FX4 F150. noticed a couple of weaks ago a slight shimmy when sitting at idle in park. Also had some rough shifting every now and again. Started out today driving in traffic and it seemed to be holding at a higher RPM range instead of shifting. Pulled into a gas station to check things out, but no luck in seeing anything wrong.

I then started having issues getting it to start again, but eventually got it crakned and came straight home. It was smoking pretty bad and had a burned oil/gasoline mix type odor coming out.

Now from all I can tell, I must have bent a rod and possibly burned up a cylinder. Times like this I'm thrilled to have an extended warranty. BUt with only 57k miles, what are your alls guesses?