help with speedometer

Is this a screw in sensor or the 1 bolt type? Speedo spiking up and down can just be a loose tranny yoke nut.

 

^^^^ 2nd this.

Is this a magnetic pickup style speed sensor? If so did you adjust the new one correctly when you installed it? Too much gap between the sensor and the tone ring would cause it not to pick up a signal. The typical adjustment is to thread it in until it contacts the tone ring, then back it out about half a turn. As long as it doesn't contact the tone ring when the driveshaft is spinning it should be ok. The service manual should have the exact spec and you should be able to download a pdf version of it right off Eaton's website.

 

I've never seen a tail shaft housing with 2 different sensors before, that odd. I've seen some with 2 sensors, but not mixed with 1 screw and 1 push in. Anyway, I suspect that your whole issue from the beginning is a wiring issue. I'd also suspect that it is close to the tail shaft, probably over the transmission, because that would be where you would have moved wires when changing the sensor. Ohm out the sensor, then remove the OEM plug on the ECM and ohm out those pins, it should be very close. If it's open or a very high resistance, then you have a wiring issue. Sometimes you can find it easy if you have someone else wiggle the wiring while your watching the meter. If you get changes when you wiggle, you in there area. That usually works if it's got a connection with high resistance, not so much with an open circuit.

 

Just out of stupid curiosity how is your volts ? I have seen a bad alt cause all of this and changed the sesnors thinking it was that. Instead it was the alt going bad and causing spikes and malfunctions thur the system. Just a thought.

 

There has got to be something that you missed. You've ruled out the ECM, so the only things left are the sensors, the wiring, proper gap and tone ring. I have never seen a tone ring fail on a transmission, only spin from a loose yoke. What codes are you getting? Any codes in the trans?

You're sure the new one is the correct part #? Did you try to put the old one back in? Sometimes new parts are bad. If it's putting out an A/C voltage then it's probably good, but I don't know the specs, it could be a signal that is too weak.

 

I know trying to do things frugally sounds great but after 11 days, I would have lost more money than the truck was worth and have had my truck down for a month on things that could have taken a day or less so I stopped trying to figure things out and go to the dealer now with all the trucks.