Name that sound (knock, clack, clank, rattle??)

[Petes]

Neighbors 7.3L IDI with 5-speed is making an intermitant knocking noise. Tempting as it was to tell him it was a spun bearing and he should scrap his truck but let me have the 5-speed first, it just doesn't quite sound like terminal engine sounds, more like it's coming from the flywheel. From under the hood it sounds reasonably healthy, under the truck there's a clack per revolution (I think). Pressing the clutch doesn't change it drastically, but ocassionaly letting the clutch out while in gear makes the noise go away comletely for awhile. The engine doesn't look like it's moving around enough to be a bad mount causing it to bang into the firewall or shrouding.

Mine's a C-6 auto, so I don't know what the clutch/pressure plate/flywheel assembly looks like, but it looked like there was an access plate in the bottom of the bellhousing. I told him to pull it and look inside for anything amis.

I made a recording of the sound from different locations. First under the truck on drivers side just behind the front wheel, then under the hood, then under the passenger side just behind the front wheel. Have a listen and see if you can name that tune. Sorry about the clipping in the audio... truck was noisier speaking into the microphone than I expected.

Thanks!

 

[FordGuy100]

Might be a bad DMF

 

[Shadetreemechanic]

Dual Mass Flywheel. My dads has been doing that for two years now.

 

[Agnem]

Time to do the lucky mod. Does it rattle or squeek on shutdown?

 

[Petes]

Yup, it rattles/squeaks on shutdown. Anyone have links already assembled to DMF info?

Thx!

 

[snowman89]

i would also look at the input shaft coming out of the transmission. mine did that and when we took it apart the shaft was moving a good half inch or so.

 

[Dsl_Dog_Treat]

Could very well be like as said, DMF issues. But those noises could be the result of something else also goin on.
A bad injector(s).

If you've got access to a pop tester, I'd get the injectors tested. If it's intermittant, it sounds like ya got an injector giving a fit or two.

 

[Petes]

Could very well be like as said, DMF issues. But those noises could be the result of something else also goin on.
A bad injector(s).

If you've got access to a pop tester, I'd get the injectors tested. If it's intermittant, it sounds like ya got an injector giving a fit or two.

I don't have a pop tester, but I cracked all the lines in turn and none caused a significant change in the rattle compared to the others. Normal engine RPM drop was pretty even for each injector cracked.

Sound sounded like most of it was coming from behind the engine underneath the truck, and not "bass" enough for a rod bearing. I'm leaning towards DMF or pressure plate related. If it was input shaft to the transmission, I'd think it'd change significantly when the clutch was engaged vs. disengaged, no?