Warpig - 1st off, Welcome to Stovebolt! thumbs_up Your 4 speed is the earlier "Crashbox" unit, not an SM420. Non-synchronized, straight cut gears and best shifted using the "double-clutch" method. It sound like you may have some internal issues with the top plate shift mechanism and/or stuck gears. You're going to need to remove/disassemble to see whats going on. You could remove the shifter top plate for an intial inspection. smile
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~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
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