I had a lot of "fun" in the garage working on my El Camino.
Evidently, 390,000 miles is the "use to destruction limit" for GM, G body speedometer cables. The cheap POS cable gave up the ghost earlier in the week. It can't even go 400K miles after 40 years!
This is the instrument cluster stripped down to the just gauges.
That little bitty screw, right of center of the photo, is what holds the speed sensor (the large black square) in place to the back of the speedometer. The wires are short, and there is very little access to remove it and even worse put it back in place. That speed sensor is vital for the cruise control, and the fuel injection system I cobbled together back in the late 90s. That is tells the FI to put the transmission's torque converter into full lockup at 50 MPH.
All back together after a short test drive. And no, the engine was not on. The gauges sorta freeze once the ignition is turned off. Well, except the voltage meter.
On the left is a speedometer I sourced used on Ebay. I sent it to a guy that refurbishment it and changed the top speed to 115, and not the idiotic 85 MPH with the giant orange 55 highlighted, like the my original speedometer on the right. And it has a trip odometer!
I dug out the original speedometer in case the newer speedometer I put in back in 2007 was bad. It was fine, so the old speedo went back into storage.
115 would be the top end speed and only if a criminal was chasing me shooting at me and he was in an old stock air cooled VW bug.
The new cable cost a whopping 40 bucks at the local NAPA.