The truck in question is a completely stock 1954 3600 3/4 ton with the SM420 4-speed stick transmission.
Does anyone else's SM420 make sounds with the clutch pedal out and the trans in neutral?
I rebuilt the trans recently because when it is in neutral with the clutch pedal out (released), it makes a sound like the input bearing lightly howling. Press the clutch pedal in and the sound stops.
I rebuilt the trans with all new bearings and it still makes the same noise. I'm starting to think that this is normal for this trans. My theory is that it's the natural sound of the spur cut first gears rotating when the clutch is released in neutral.
I've never been around another truck with this trans, so I don't have another truck to compare it to.
Rob
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