Red/Black should be gauge power to all the gauges.

Well, red/black wrings out to be one of the two wires to the sender in the tunnel. I have found over the years that the wiring in this car is not exactly what is in the Bentley manual.

Well, if it helps, this is what it should be doing. (looks like you have it)

http://forums.pelicanparts.com/uploa...1621822986.JPG

That's what I have. Red 12V wire I ran from the fuse box, and the two signal wires are on - and 31b. Nothing on A, and the speedo can is grounded.

The speedo sends a voltage down the sensor wire to the reed switch. The other wire from the reed switch is grounded. Porsche brings it all the way back to the speedometer to ground it, but I don't think that is electronically necessary, because this is just an on-off-on-off etc signal. If there is a benefit of doing the grounding at the speedometer, it is that it doesn't matter which wire of the pair is the sensor wire, and which is the ground. Whichever way you connect the plug back by the shift coupler, or which lead you connect at the speedo, it is OK.

Assuming all the wires are solid, and no shorts somewhere. And assuming the speedo works.

The simplest test of the speedo is to hook up a short wire to the sensor terminal on its back, and, with the ignition on, tap the wire on a ground. If the speedo works, then the issue is in the wiring or the sensor.

Your ohmmeter beep test ought to confirm if the wires are patent, and if the sensor is working.

So just remember - it works by grounding and opening a circuit.

The 1977 911s had a speedo designed so it could be used on a positive ground or negative ground system, which involved a jumper from the grounded case to the electrically separate speedometer part. If you didn't connect the jumper on your 911, you burned out a diode in the speedometer (not all that hard to fix, though, if you like doing that kind of work). But my recollection of my current speedometer - for an 80s SC - is what you'd expect.

It is a bit unlikely that whoever rebuilt your tranny left off the speedo magnet piece, but possible. I'm not sure just how one might test this - put a magnet in the sensor hole, and feel if it reacts while you turn the axle?

Occasionally one or a few of the 8 magnets will fall off inside. But that should just give bad (low) speedo readings.

Thanks Walt
After I tested everything with my magnet and drill and put the sensor back into transmission and let it run and gear it did nothing for like 30 seconds and then started working I have no idea why.
Pat

Drove it to the upholstery shop today. Speedometer did not work at all. I will deal with it in two months when I get back from summer vacation. Tach works OK. No boost gauge operation. AEM AFR gauge isn't working either. What a pain.