This isn't my Jeep, but my noise is 100% identical to this one.


Last night, I removed the flex plate inspection cover to try and tighten the torque converter. That was obviously the easier thing to do, so that's why I tried it first. No luck, that knock is still there.

Has anyone else had this exact style noise and knows what it is?

 

Did you shine a light up there and inspect the flexplate for cracks?

 

Yeah, I honestly didn't see any.

One of my friends suggested that it could just be one set of rod bearings expanding to out of spec when heated up. Does anyone know if that's a common problem?

The noise only happens when the engine is WARM. When it's completely cold, there is no knocking sound.

 

Nah. Rod bearings are worse when cold and rapidly get worse in a short period of time.

 

I tightened my four bolts yesterday, 13mm 10" box end by hand, too obstructed to fit the torque wrench. Tight but not reefed! Each was backed out about 1/32 to 1/16"
Then restarted, wow no rattle. Checked flexplate for cracks also, none.
Could your noise be from some broken sections inside the cat converter? or some exhaust leakage from a cracked exhaust header? Is the exhaust pipe in contact with the trans support crossmember? Does your trans perform well, could there be a failure occurring inside the torque converter?

 

I can say I've had that same noise for the last 20,000 miles. Hasn't changed a thing still same power, mpg's, everything just makes a little more noise

 

Me too, no change in power or mpgs.

 

It's not exhaust. My exhaust is all in great shape and tight.

The transmission performs better than I could even expect from it. I honestly think the noise is coming from the bottom of the motor. It can be heard best from the oil pan area.

 

So I used a hollow piece of stainless steel tube as a stethoscope. I put it all along the bottom of the oil pan where all 6 cylinders are. I heard nothing.

Then, I put it against the flex plate inspection cover. The knocking sound was as loud as could be.

Now... I already tightened my torque converter as tight as I could possibly get it.

What could possibly be making the sound?

 

Try this:

Straightshooterjeeps cracked flexplate diagnosis

I removed 3 of the 4 bolts.

Then loosened the last bolt about half way.... I left this one in to maintain connection between the tq and the plate. Just so I wouln't have to fiddle with putting bolts back in too much.

Now the flexplate is pretty much seperate from the torque converter.

Got my flashlight pointed up in there

Grabbed a big flathead screwdriver and started prying on the flexplate

Don't see anything yet

Turn the flexplate a half rotation

Pry again

and there it is! A big fat crack up near the center of the plate.

When the flexplate is loose from the torque converter you can get it to "flex" real good and you just might be able to spot your crack.

Just to be sure you do have one before dissasembly.

It was very obvious at this point, but before pulling those bolts I looked and looked and could never see a crack.

Hope this helps save someone a little time.

 

I'll bet you it's probably cracked.

I think I'm gonna tear the whole thing off and see what's up.

The last time I was down there without everything apart, there was like one inch of space to work in.