Flywheels or flexplates as they are often called for automatic transmissions, don't have much mass at all. Their purpose is mainly to translate the bold pattern of the crankshaft to that of the torque converter and to provide something that the starter can engage with.

 

I had the same thought as you - if we have to put a new flywheel in, might as well see if there are any upgraded or alternative options out there. But I ran into two issues here
1. I couldn't find any options readily available, so I'd probably have to get one custom made (not doing that).
2. Similar to what RJ and CC said, the stock flywheel appears basically as light as you'd want it. It's not a completely solid surface; instead, there are six spokes in the middle connecting the center hub that bolts to the crankshaft to the rest of the outer flywheel (of course I assume this is all one piece of metal, though). So, I can't image saving much more weight that than without making serious durability sacrifices.

The bad news is that new flywheels (NCA1426CD) are NLA. But used ones are pretty available and not expensive (< $100 usually). Of course, labor is gonna suck. But, I was prepared to sign off on an engine replacement, so...I'm ok with it.

 

My experience is on GM 350, but should translate, flexplates crack around the bolt circle when the transmission to bell housing are loose, they will then keep running for awhile but you usually get a rattly noise at idle, like gravel in the bell housing. Eventually they let go. Maybe in the past your transmission loosened up to the bell housing? I’ve only seen it happen when a couple bolts loosen up.

 

Hmmmm...thanks for the info. Car was completely normal for until all of a sudden it wasn't. But, maybe the theory still holds...wonder why the bolts would loosen up?

 

Murphy, and remember, Murphy was an optimist......

 

Here’s the broken flywheel. My guess is that at some point over the last few months one of the spokes cracked, and then it was a domino effect from there as the remaining spokes had to share more load.

Gonna get this framed and put on my wall, I think.

For those wondering, this thing is quite light. Like 7 pounds it feels like.

back on the road for now

 

That's a failure you don't see every day. Definitely worth framing.

 

Thanks for sharing! I'll take one of those any day over the more ominous engine failure modes.

 

Never seen that before - any chance that the starter engaged - though I can not see any broken teeth.