[bbchevy]

Bought something to play with and its playing with my head. Its an interesting problem.

The Truck
99 1500 Z71
Shortbed step/style side deal
5.3
4L60E
Posi 4.10's
268,000 miles

The History...or story behind it
Engine was "replaced" at unknown mileage and has unknown mileage
Runs beautiful, powerful, and quiet
Transmission could be second or third but the truck is so clean it could almost be the first haha
Truck is pretty tight all around.
Tow haul works
Transfer case was pretty low

I've been driving the truck for about a week. Drove it 3 hours home when I bought it with no problems. Yesterday morning I checked the transfer case level again and it was a little low. So I added a little. That night drove it two miles and the speedometer started tweaking out at 30 mph. Then the trans started to freak out. Downshift then upshift to 3 then rev out then catch in third again and so on. Turned around went back. Next day tested it again and it started freaking at 20 mph the second started getting confused. So I changed the VSS (vehicle speed sensor) and it affected nothing. Totally the same.
And this all started with no warning. Bad reluctor ring or whatever it is.? It doesn't feel like its a mechanical problem as much as it is a communication issue... maybe? What's with the speedometer?

Oh and with a scan tool hooked up it records the same whack reading that the needle says. Can't isolate trans though.
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