[lsversaw]

Sonoma, all new 10 ga wire, solid or stranded, should have the same conductivity. There will be far more variability in the connection between wire and connectors than there is in the wire itself. So...

My theory is that your new 10 ga wire from the battery to the terminal block initially had resistance in it due to incomplete crimps. When you soldered it (good move!) you removed the rouge resistance.

But my theory requires that the starter solenoid moved enough to click, but not enough to close the contacts that engage the starter, due to voltage lost through the connector/wire interface. Hmmm...

Question for Those Smarter Than Me (like Vette Vet!): is it possible that the starter solenoid can click but not close the starter contacts, especially with less than full voltage?...

...AND is it possible/likely that Sonoma has a marginal starter solenoid that works fine with full voltage, but gets stuck halfway when voltage is low? If so, then Sonoma may have a reason to replace the starter soon, before the solenoid goes from marginal to bad.