The shavings on the first rear axle sensor suggest there are bigger chunks in the diff, which might bounce up on rough roads & cause the shifting problems. I'd pull the cover & check out the gears & bearings. Use a flexible magnet to fish chunks out from between the pinion bearings, going over the top through the oil journal. Getting all the sediment out of the rear lip is just a nasty job, but it has to be done. Another likely cause for the shifting problems (assuming the speedo is also erratic simultaneously) is the 4WABS module going bad - it happens. But it's easy to bypass for diagnosis (or semipermanently) by installing 2 jumper wires in the unplugged connector.
The seat belt wiring is strictly for the chime - it has nothing to do with SRS.
And the SRS is not related to the transmission, other than at the fuse block & battery.
I'm glad you already replaced the alt & battery cables - I noticed the crappy clamp in the 2nd photo.
I also noticed that, when you pulled the carpet, you left the shoulder reel covers on. They need to come out for thorough cleaning; particularly the driver's. Read these captions:
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The best replacement insulation for the bedwall panels would be common cut-pile carpet. Spray adhesive on the panels where the original was, then stick the carpet pile (not the backing) lightly to the panel.
This explains the temperature sender:
But if you've already found coolant system problems, then it's likely that the pump has also been damaged.
You can check it by disconnecting the heater hose that comes from the intake, at the heater core, and starting the cold engine. If the pump shoots a stream of coolant out of that hose (aim it appropriately), then it's OK. If not, there's either a pump problem, or blockage in the coolant journals in the block.
