6.0 slow crank/no start

[Mustang1989]

I haven't started my truck since this past Saturday, and it's been parked outside the whole time in -15 F to just above 0 temperatures. I go to start it, let the glow plugs warm up for awhile, and it slow cranks and eventually dies with what I assume is the starter screaming at me. The batteries are good. I plugged in the block heater for about an hour before trying it again, but got the same result. The weird thing is once I remove the key all of the gauge needles vibrate in place for a few seconds? Any ideas? I can get it on video if need be.

Thanks

Update: The batteries were actually dead.

[gblauf]

The cold is brutal on batteries, it will never start if it is cranking slow. Try jumping it and see if it spins faster.