I just swapped in a low mileage '87 A340 Auto tranny with a new torque converter to replace my weak original 85 auto. The newer transfer case has a sensor with 2 wires that did not exhist on the older transfer case otherwise it's an exact match. I assume my transmission controller and computer won't even recognize it and maybe I should just unplug it, but I would like to know what it is and how it fits into the big picture. Does anyone know what this sensor is, and why it's not on the '85?

 

usaly there is 1 sensor on the t-case...the 4WD light sensor

 

My 85 is not an SR5, very basic pkg I don't think I even have a 4wheel drive light.

 

All 4x4's had a 4x4 light

There should be a few sensors in the 87 t-case that are not there in the 85, and I believe it has something to do with the ETC. not 100% sure tho

 

I know my trans. has two Vehicle Speed Sensors, one on the side of the trans. and one where the speedo gear is at the rear.

 

This transfer case has one sensor, perhaps the 85 setup got it's source from the shifter instead of the t'case

 

Got pics?

 

Here is a picture thank's for your help

 

Yeah looks a lot like this 4WD indicator switch from a gear driven t-case. If so, it just switches the dash light on.

 

I would bet you are right, if my light doesn't work then I will find the circuit and wire it in.
Funny though the 85 must have pulled it's source from the shifter or some other way.