I have a88 bronco 11 that want shift in to od had trans rebuilt did great blowed head gasket ggt that repaired now want shift in to od

Any help

My 89 bronco 2 wouldn't shift into overdrive. I heard that a vehicle speed sensor (vss) can make it where they wont shift into overdrive. I got under the truck, took off the skid plate under the transfer case, and I wiggled this black round plug thing with wires coming out of it ( I think it was the vss). Drove it around the mile sections and It Shifted into overdrive. I Haven't yet replaced that part because Od is working and if it aint broke, don't fix it.