The picture on left is the one the salvage yard says is supposed to be in my truck according to build code. The middle picture is of the front Diff I just removed. The one on the right has both picture with arrows pointing to the differences. Build code says GT4 which is 373 ratio. Got used one from salvage yard and they claim it should match my build code however it is different. My unit only has one plug for the motor that switches the front diff but the replacement one has 2 plugs. One to a motor housing and the other to something that looks like a sensor. Of some sort. Any help in identifying would be appreciated. They are definately different.