bigbadon

Yours is Not what a rod knock sounds like. Listen to other 4.0s some are quiet but I hear this same type of noise in a lot of them. Some are very subtle and you have to listen closely and others are more noticeable. Mine is more noticeable when hot and goes away above 1200 rpm. A rod would increase with rpm and would also knock at a faster rate. That knock is half the crankshaft speed so I would suspect something in the valve train. Flexplate noise will vary in frequency with load.

redmuck

sounds damn near exactly like mine.

cruiser54

See post # 14?

redmuck

ok cruiser, wouldnt mine be the flexplate or broken piston skirt?

cruiser54

Have you checked the flexplate for cracks as outlined in that post?

redmuck

no not yet,i know i need to. along with everything else i need to do.

cruiser54

1/2 hour job.

bigbadon

You guys got me thinking so I checked my flexplate for the heck of it and it was OK. I have the normal piston slap when cold that goes away quickly. When it is hot it sounds just like the OP video. The noise is synchronous with 1/2 engine speed. With a stethoscope it is loudest at cylinders 3 & 4 on passenger side of block around lifter area.

cruiser54

What are you using for oil and filter?

bigbadon

Fl-1 and Rotella 15-40 on last change....was running supertech 15-40 before that and it was about the same

cruiser54

Who makes FL-1?

bigbadon

Motorcraft is the brand name. Have also tried Wix,Purolator and AC....all had same results. My noise is subtle, you have to turn the radio off to hear it or be outside of vehicle. On a hot day it gets pretty noticeable.

cruiser54

Good to know. Piston slap is pretty common on these. Can you pinpoint the location?

bigbadon

Around 3 and 4

cruiser54

Valve cover or oil pan?