Heat Cracks in Flywheel (1 Viewer)

[WildernessRimFab]

Stock 72 FJ40 with 1F and 3 spd trans +tcase. I'm in the middle of a clutch/rear main/oil pan gasket job.
Below is the picture of my flywheel after getting it resurfaced. There are small heat cracks all over it which didn't fully machine out. You cant feel the cracks with a fingernail.

Any problems putting this back in? Ive read horror stories about broken flywheels in drag cars, but wondering if that has happened to anyone in a cruiser?

Obviously I can replace it, but do I NEED to replace it?

 

[Rock40]

It's ugly but the chances of it coming apart are small in my opinion. It's not turning 10,000 rpm after all. I'd be more concerned about what exactly led up to all that heat. Was the pedal height and clutch slave adjusted correctly? Is somebody riding the clutch? Under "normal' conditions, it shouldn't get hot enough to crack all over the face like that. My bet is the clutch disc was in pretty sad shape.

 

[brian]

Just fine run it

 

[WildernessRimFab]

I agree with the small chance of it coming apart at 3,000 rpm. The clutch worked ok for the last 3 years when I have owned the rig.

Is somebody riding the clutch?

Lets just say that the PO wasn't exactly a rocket scientist.

As to the source of the heat, I think a PO had the wrong clutch disc installed. The springs protruded out pretty far from the engine side of the disc and had "self clearanced" on the flywheel bolts. No the clutch wasn't installed backwards. The springs on the old disc stick out much farther than the springs on the replacement aisin disc. The old disc is the correct diameter and the same thickness as the new one. The old disc doesn't have a manufacturer on it, only a number. The OEM ASCO pressure plate was installed with this orphan disc.

 

[Spike Strip]

Small cracks in the disc contact surface prolly ok... I'd be worried about cracks around the bolt holes.

 

[WildernessRimFab]

No cracks elsewhere on the flywheel. The visible marks near the bolt holes are scratches from my fight with the locking tabs.
Thanks for the advice everyone - I'm gonna run it and its going to be fine.

 

[sadam_husain]

as the above posts it'll be fine, I wouldn't be putting it in a million HP drag car that's an entirely differently application but will be fine for an old 40 series cruiser chugging around for another 40-50 years of faithful service