Flywheels and pressure plates can get hairline heat stress cracks if you are really hard on them (lots of slippage).

I too think it would have been noticed last month before and after it was surfaced. Unless you slip the clutch lots it should not happen in a month. Do you sit at a stop light on a hill holding position with the clutch and not use the brakes?

Unless the cracks were extremely bad, enough to make you think it was unsafe to reuse, I would not expect the minor surface cracks to cause chatter. Sometimes new clutches will chatter some until they have time to seat in. Often this chattering can be avoided by driving / clutching style, and then before you know it, no chatter even if you try.

Lets see some pictures of this flywheel.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-