Do you have a strange knocking at idle?

[FLWookie]

This came out of my 06 tundra, but same engine so I assume same flywheel. I had been hearing a light knocking that at first I thought was an exhaust leak or an injector, hard to locate. Then, I thought it might be the ac comp since the tone would change when I disengaged the ac. It finally got so bad that the truck sounded like a diesel at idle and shook the mirror so bad at highway speed that I had to take it in.

Turns out my flywheel was nearly sheared off from cracks fully around the center bolts and a smaller crack forming at each outer bolt.

Cracked 4.7 flywheel

• FLWookie
• Aug 6, 2017

Cracked flywheel

• FLWookie
• Aug 6, 2017

Cracked flywheel

• FLWookie
• Aug 6, 2017

It probably only had one more small drive on it before it ce loose and trashed my bell housing/block/transmission.

 

[FLWookie]

I'm going to x-ray it at work this week and I'll post those pics as well.

 

[abuck99]

Yikes- Ive heard of flex-plate (flywheel) issues on the 4.7L but never have seen the result.

 

[FLWookie]

Yeah, I meant to say flex plate.

 

[2001LC]

I too remember reading in mud some time ago of this, but it's must be rare. Seem was vibration someone was tracking down, IIRC.

 

[abuck99]

I think Spresso has some experience with this if I recall.

 

[Spike555]

This is common on Duramax engines, I've never heard of it on a Toyota.
Thanks for sharing.

 

[FLWookie]

This is common on Duramax engines, I've never heard of it on a Toyota.
Thanks for sharing.

I could understand this in a high torque application, but my tundra only ever made 300lbft

 

[K5Guy]

I think this may be happening to me I though i had an exhaust leak but today the noise has changed to a constant metal on metal noise. not real the diesel noise you described do yall think it could be the same thing? it almost sounds like the torque converter is rubbing something.

 

[FLWookie]

I would definitely inspect before it gets any worse. If it comes apart while driving its going to toast your transmission and possibly the bell housing (not sure if its separate on these transmissions).

 

[spressomon]

Robbie replaced the cracked Flex Plate in my 100's 2UZ-FE 2-1/2 years ago. But the real pisser: The brand new Toyota OEM flex plate is the same design & construction as the old ... bummer Toyota has not not bolstered the failure points.

 

[K5Guy]

I would definitely inspect before it gets any worse. If it comes apart while driving its going to toast your transmission and possibly the bell housing (not sure if its separate on these transmissions).

i think it is one piece so that would be a bad time. I am hoping it is just a loose flex plate bolt but i'm not usually that lucky. i looked at the plate its self yesterday but could not see anything that looked bad, going to look again today.

Have you heard of the starter making contact with the flex plate and making a noise?

 

[K5Guy]

after looking at it again i think it may be the starter not retracting all of the way back in. the front of the flex plate looks like it has been rubbing something and i think that might be the starter. I can not think of anything else it could be contacting while its spinning.

 

[looking4lc]

can someone describe the knocks to me? and where the flex located to inspect?
i hear some weird knocking/ticking when the car idle from the front passenger' tire well.

 

[spressomon]

You can probably inspect it through the access plate (remove) on the bottom of the bell housing. If you have an inspection camera scope... all the better.

 

[FLWookie]

after looking at it again i think it may be the starter not retracting all of the way back in. the front of the flex plate looks like it has been rubbing something and i think that might be the starter. I can not think of anything else it could be contacting while its spinning.

If its cracked, as it spins and torque is applied it will flex and contact either the bell housing or other bolts in its path. I wasn't there when mine was replaced so I can't really say what the inside of the BH looks like.

You're not going to be able to see any cracking since it's behind the torque converter or under the mounting bolts, unfortunately. But, if the car is idleing you should be able to pull the inspection plate and rear a noticable increase in volume if the knock is coming from the transmission, vs an exhaust leak further forward in the engine bay.

 

[K5Guy]

You can probably inspect it through the access plate (remove) on the bottom of the bell housing. If you have an inspection camera scope... all the better.

i did that already no scope but used my camera and flashlight and dint see anything alarming. other than some wear marks on the front of the flex plate teeth like it was hitting something.

 

[K5Guy]

Thank you for the responses guys, I know i kinda highjacked this thread.

A strange thing happened today and the noise stopped suddenly so not sure what to think now.

 

[spressomon]

Ok, a little more backstory: I had what sounds like a similar knock especially noticeable at or near idle. I had Ben & Joe at Slee listen to it, Robbie and a couple of my regular LC travel buddies and everyone concurred it was probably the flex plate. Well, it wasn't. The knock was still there after installing the new flex plate.

But, unexplainably, the noise went away and the engine just purrs so smoothly and quietly today.

 

[Keowee]

^^^Could it have been carbon build up on a piston?