Speed Sensor (Geared Or Magnetic)

[BHIGG02]

I have a 1992 Chevy Pickup with 700r4 tranny that was changed out. The speed sensor that was originally in it was electronic/magnetic pickup and the one that's in it now is an electronic/geared.

Does anyone know if my computer and the speedo in the dash will work with either one of these sensors? Or do I need to change it back to the magnetic sensor? And if i do change back will I need to change the whole tail piece or can I get the metal piece that goes on the shaft for the pickup?

Any help would be greatly appreciated.

Brian

[mr_mushroom]

if the output pulse count is the same, then yes, it will work fine with no problems. if said output pulse count/mile is different, your computer or speedometer may need to be recalibrated.
you can do this yourself with an ALDL link for a laptop, or most shops should be able to do this for you.
if the speedo needs recalibrated, there should be a connection on the back of the speedo for this. i don't know if the factory speedo has this or not though, as mine was OEM mechanical and the new one is aftermarket electrical, and it has a 'recalibration' function if you hook up a couple of wires to the back of it.
let us know what your progress is, and any new info you come across.

[BHIGG02]

So if it doesn't matter which sensor I use then this means I have a bad sensor.

I'll let you know what happens after I replace the sensor.

Thanks for the prompt response.

[mr_mushroom]

maybe try that.
i can't be 100% certain, as my tranny uses a geared mechanical sending unit, and i've placed a hall-effect converter behind the dashboard that switches it to an electrical send.

edit:
and also you can just get the part that goes on the tailshaft, though you will need to drop it to make the switch. changing the external housing is for replacing the driven gear count on mechanical send units.

[BHIGG02]

Well, I replaced the sensor and it still doesn't work. I don't think their compatible.

Any suggestions?

[davepthomas]

so did you come up with a solution to your dillema? i'm in the same situation at the moment. i bought an '88 chevy pickup for $500 with a burned up tranny. i bought a 700r4 at the salvage yard for $200, it was out of an '85 caprice. everything looks identical except for the speedometer. the plastic drive gear on the mechanical speedometer is replaceable, the metal magnetic gear on the electronic speedometer looks like it's pressed on. anyway, the gears are absolutely not compatible with each other. you either have to have the magnetic gear for the electronic, or you have to have the plastic gear for the mechanical. anyway, i removed the plastic gear from the tail shaft of the tranny that had the mechanical speedometer, then i tried to remove the magnetic tooth gear from the tranny with the electronic speedometer pickup so i could swap them and the tail shaft housings, but i couldn't get the magnetic toothed gear off the shaft. did you have any luck with your situation?

[BHIGG02]

Unfortunatlly, I didn't resolve my problem with the speedo, my speedo goes up to about 5mph at about 75mph, I would say I'm pretty much without a speedo.

I was told that output pulse or voltage of both the sensors was the same regardless of the pickup being geared or magnetic. If this is true then my speedo should be working. Not!

[davepthomas]

okay, i went to a tranny parts store today and i bought the part to put on my tranny. you have to take the tail shaft off the end of the tranny (4 bolts, and a big reusable o-ring) you have to undo the clip that holds the plastic drive gear in place pull off the gear and the clip, then there is the part that i bought for $6 it's called the "relucter", it looks like a metal gear. it goes on dry, probably install with a pipe and a mallet. the one i bought from them was used and a had some tool markings on it from the removal process (hammer and punch), but they said people (tranny shops) come in and buy them about 10 at a time for this same reason. obviously you have to install the pick-up coil to read the relucter for this to work.