The clamp is fine....I thought it was the clamp after putting a new T nut and then trying to tighten down on the posts, which got it tight but had some slight movement. So I said, I'm sh1t up a creek, it must be the clamp, metal compressed over the years....and the nut/clamp ain't biting into it.

I dumped a loaner battery in the car, just so I could at least move it, and it tighted up just fine...and both batteries *depleted and loaner* are from the same make...

Go figure

Removed negative cable and MM looks good from end2end