The Stovebolt Site Forums The Shop Area Engine Shop Flywheel specs 1939 JD (3/4 ton)

I’m having my flywheel resurfaced, however a minimum thickness would much appreciated if anyone out there can answer this for me. Thanks in advanced.

How worn is the flywheel? How much do you expect to need cut off of it? When a flywheel is resurfaced, both the disk surface and the pressure plate mounting surface get ground down the same amount. So from that aspect, it doesn't matter. I don't know of a minimum thickness spec. It usually doesn't need much taken off to clean up a flywheel.

But the clutch disk hub extends into the center recess where the flywheel bolts to the crankshaft, so it has to clear the bolts.

You might be able to place the bolts in the flywheel mounting holes with the heads toward the disk, then put the disk on the flywheel and see how much space is left between the bolt heads and the disk hub. Maybe use some plumbers putty to make the measurement.

I'll move your post over to the Engine forum where it'll be more on topic.

Farm Boy, I've done a fairly exhaustive search of my Chevrolet books and resource documents (shop manuals, parts books, dealer ads, GM Heritage documents, etc.) and can't find anywhere listing the original thickness of the flywheel for your truck. Most information I have read indicate it's safe to remove from 0.020" to 0.060" thickness from a most flywheels when resurfacing, but without knowing if yours has been resurfaced before, hard to say how much your shop can safely remove.

Perhaps there is another Bolter with knowledge of your flywheel dimensions that will chime in to try and answer your question?

I have a spare flywheel from a 216 in the garage I could measure for you, but that really won't tell you much. Other than the clearance between the flywheel bolt heads and the clutch disk issue, I think there wouldn't be a real minimum thickness. Flywheels are pretty robust, unlike brake drums that have a maximum diameter for turning.

FWIW - There is an NOS flywheel that fits your truck listed on eBay. Maybe if you contacted the seller, they would be kind enough to measure that one and give you the dimensions so you can figure out if yours can be resurfaced or maybe that NOS part would fill your need???

PS - Ignore the typo in the sellers ad listing. It's a 139 tooth, not 193 - hahaha!

That one for sale looks identical other than the PN to the one I have. I'll measure mine a little bit later today and post measurements.

OK, here are some measurements of the flywheel I have. It's used, but no idea whether it may have been resurfaced.

Thickness at rim -- 1.17" (may have originally been 1-1/4" rough casting before factory machining.)
Flywheel mounting (crankshaft side) is ~1/4" below rim.
Flywheel mounting (clutch side is ~1/2" below wear face
Thickness at flywheel mounting ~0.45"
Back surface of flywheel mounting to clutch disk springs - 0.95" (from previous dimension, that leaves ~0.40" from clutch side of flywheel mount to clutch disk springs.
Disk lining (used disk) is about 1/16" to the rivet heads. That much could be allowed for wear before the flywheel to crankshaft bolt heads would hit the disk springs.

Per the attached picture (sorry about the teeny tiny text, you'll need to blow it up to see well,) there's 0.258 between the wear surface and the bolt heads and the disk springs take up about 1/16" of that space. And probably where you should think about replacing the flywheel, there's a machined ring just inboard of the clutch disk wear position that's 0.015 below the wear surface. If that ring starts getting cut, that might be a good stopping point for resurfacing.