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Flywheel Cracks

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ndnchf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Topic: Flywheel Cracks
    Posted: 31 July 2020 at 12:22pm
A buddy gave me this flywheel. Just to save some time, I figured to change the ring gear and have it ground in preparation for a trans/clutch swap.  But I'm seeing a few cracks from the inner edge, roughly a inch long.  Reading up on the subject, it seems heat cracks are quite common and some folks say it can be ground and still used.  I don't know the condition of  the flywheel currently in the jeep, but won't be surprised if it has cracks too.  Apparently its not uncommon. 
 
What do you guys think of this one?  Have it ground and use it?, or make it into a boat anchor?
 
 
1948 CJ2A - It goes nowhere fast, but anywhere slow.
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Oldpappy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 31 July 2020 at 12:28pm
Doesn't look too bad to me. I would have it ground and use it.
If you can't get there in a Jeep you don't need to be there
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Mark W. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark W. Quote  Post ReplyReply Direct Link To This Post Posted: 31 July 2020 at 10:00pm
The machinist will be the one to tell you ya or nay. But to compare the Disc brake rotors on my Dump Truck and Pup trailer get these same kind of cracks and they are only replaced if the crack goes from one edge to the other. Little cracks in the middle are just watched. 
Chug A Lug
1948 2A Body Customized
1949 3A W/S
1957 CJ5 Frame Modified
Late 50's 134L 9.25"clutch T90A D18 (1.25") D44/30 flanged E-Locker D25 5.38 Since 1962
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duffer View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote duffer Quote  Post ReplyReply Direct Link To This Post Posted: 31 July 2020 at 10:34pm
The apparent crack that would worry me most is the one that appears to radiate from the pilot bore headed to the adjacent mounting bolt hole.  If that is indeed a crack, send the flywheel to the scrap yard.  I'm not sure an analogy to a brake rotor is a good one.  The flywheel rpm's are much higher and if you have ever seen what happens when one actually comes apart, IMO, it just isn't worth it.
42 gpw, 47 2A, 49 3A, 55 3B, 68 CJ5, 5 FC's, 2 wagons, and sort of a Jeep-2012 JKU-R
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug. 2020 at 1:22am
I concur with duffer on this one crack. However, it may just be a deep scratch or a gouge. It is hard to tell from these two pictures.

Be sure to point that one out to the machinist. You do not want to experience an exploding flywheel!

The cracks on the surface of the flywheel where the clutch disc engages that do not extend over the edge of the recess, (in the center of the flywheel for the crankshaft bolt circle), are not issues. However, the ones that do extend over this edge are a concern.

Be sure that the machinist also evaluates these ones as well.

IHTH, Cpt Logger.

PS. I am a certified NDT, technician. (Non-Destructive Testing), IE: Magnaflux & dye penetrant among other forms. I am not bragging, I am just trying to help you sort out what value to put on my advice.

PPS. The crankshaft bolt holes at 8:00 & 10:00 in the first picture appear elongated, are they?
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ndnchf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug. 2020 at 5:59am
Thanks guys, I appreciate the replies and insight. The pilot bushing appears to be staked for security. 



I see no cracks around it. None of the bolt holes are elongated, its just the camera angle. This flywheel seems to have had very little use since it was last serviced. There is no perceptable wear from the clutch disc and the pilot bushing measures .629" which is just right for the mainshaft's .6265" pilot. Even the ring gear is in pretty good shape. But I heated and removed it last night. I have a new one if the flywheel turns out to be OK.


1948 CJ2A - It goes nowhere fast, but anywhere slow.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeeper50 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug. 2020 at 10:19am
How bad is the tooth wear on the starter ring?  We used remove them and reinstall with the good side of the teeth facing the starter. Good to go- we did that on the old airline bag tugs for years no issues

Edited by jeeper50 - 01 Aug. 2020 at 10:22am
'53 Cj3B 4 cyl,clifford research header, D25/D44 lockrights,11" brakes, Belleview ol skool winch.


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ndnchf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug. 2020 at 10:37am
I've not pulled the trans yet. This is an extra flywheel a buddy gave me. My idea was to have it serviced and ready to install. The ring gear was not too bad, but I have a new one. I removed the old ring gear last night.  But I won't install the new one on this flyheel until I get the machinists ok that it's good to use. If it's not, then I'm hoping the original flywheel will be ok.
1948 CJ2A - It goes nowhere fast, but anywhere slow.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug. 2020 at 10:54am
If it is bad, they make great tool stands for grinders and such.

If you can't get there in a Jeep you don't need to be there
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SE Kansas 46 CJ-2A Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug. 2020 at 11:47am
Make sure that the tooth count is the same as your old ring gear if you end up replacing the ring gear. There are two different tooth counts for ring gears.
46 CJ-2A #64462 "Ol' Red"

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ndnchf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug. 2020 at 12:07pm
I just got back from the machine shop. His recommendation was to not use it.  He likes vintage stuff and tries to save original parts whenever possible. But because of the crack pattern, location and depth, it would be best to retire it.  So I'll follow his advice.
1948 CJ2A - It goes nowhere fast, but anywhere slow.
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cpt logger View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug. 2020 at 6:28pm
Good call.

I hope your "original" one is repairable. If not, good used ones are available.


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