thanks seanr, ill upload some photos tomorrow, i have to find a victim to spin the tire tomorrow. Or I can try and spin it myself, i probably will have to make something to plug into the two pins.

 

Almost everyone that rebuilds these automatics simply removes the differential section and sets the entire assembly it to the side.....doubtful that anyone was inside to screw anything up.

Of course, my point is simple.....when is the differential going to get rebuilt, if you don't do it when the transmission is apart?

 

If on jack stands, you can start the car and spin the rear tires....then all you need to do is watch the multimeter.

 

greg, i did not think to many people rebuild their differentials, can you take it off without taking off the transmission (doubt it)? that is a good question. I really don't know. when should I get it rebuilt? what are symptoms of needing a differential rebuilt? thanks

 

you can remove the differential from the transmission on a auto.

BUT the rear cross member will have to dropped first

Also setting up the pinon to ring gear is a bit tedious as the pinion will stay on the trans.

Otherwise if you dont hear any gear grinding or whining fill it with oil and drive it.

 

The speedo sensor is visible and appears to be mounted correctly in post #12. The sensor wire harness connector is visible and appears intact in post #22. You can do what Greg in post #33 to verify whether the sensor is working and getting a magnetic pulse from the diff. In nearly all cases, if the connector is intact the sensor itself is the problem. Although failure of the magnetic ring inside the diff happened in George Suennen's 90 S4, as George and I found, I can't see it happening in an 89 or earlier due to the way the ring mounts, but who knows? In george's case, we replaced the sensor because it is the #1 suspect. When that failed to restore the speedo/odo, we unmounted the sensor and simulated the magnetic pulse, as I mentioned, with a sanding disc to which a few magnets (removed from an old computer hard drive), and voila, we saw the speedo working. The faster we spun the disc, the higher the MPH on the speedo.

Anyway, it's awfully coincidental that the speedo system failed with the tranny rebuild. In order to complete the rebuild of an auto tranny, the diff must be removed. If this is a shop that has a lot of 928 trannies being rebuilt (which would be highly unlikely), you can't rule out that perhaps the wrong diff cover was reinstalled, giving you a version of the problem I had. BUT, my eyeballing of your picture in post #12 leads me to believe you have the correct cover. Or perhaps the wrong diff itself was reinstalled. Again, highly unlikely, but why the speedo has failed immediately after a tranny rebuild leaves you wondering. The most likely cause still is the sensor. I see the connector is still screwed to the wheel well area. They may have not opened the connector or removed the sensor from the diff cover as they lowered the tranny out of the car, stressing the wiring, until they noticed the sensor wiring was preventing tranny removal.

So, test the sensor as Greg and others suggest with a multimeter while the rear is up on jackstands and the engine is on and the tranny is put in D so the rear wheels are turning. If you see no pulses, replace the sensor. If you see pulses, the problem is somewhere between the connector and the speedo.

 

I plugged my multimeter into the red and brown wire pin holes. it said 0.0 and beeped continuously, after i drove it around it did not stop continuously beep it was just like one long beep. here is what the multimeter setup i used look like.

 

Now move the sensor away from the dif cover and see if it stops beeping.

 

i think i might have connected the multi meter to the wrong wires.

 

here is the image of the second setup, their were no beeps at all. I am not sure what do do know.

 

thinking about it one of the two sets of wires has to be the correct wires. so one set made nothing but a sound, the other made no sound. This means their was no pulsing so the sensor has to be bad. can any one confirm this?

 

Alright so all I need is P/N 928.606.210.01? The diagram on the internet is a little strange, it shows the speedometer as being grouped with the pod cluster.

 

Before start throwing parts at it, are you 100% sure you got the right connector this time?

 

Imo000 yes, the first one I tested had brown/red wires, that went into the car probably into the dashboard to the speedometer, the second one i tested the for the sensor.

 

That's the speedo sensor, 85-90.