I want to share some troubleshooting about this problem. Every once in a while my gear trouble light would pop on for a few seconds and then off. There is no speed shift while this light is on. Then last fall the joystick broke in half, not sure how this can happen but 6 wires run up through that handle to the shift buttons. This machine has 8000 hrs on it. I epoxyed it back together very nicely, and strong. Later last fall the gear light stayed on for good and checked the codes by pulling the harness and shorting pin 1 and 2 and I got a code of 251, left track sensor. I found the original sensor cat has them for $300+ . Or you can buy them online, hundreds of machines use them and they are easily accessible from many vendors for about $70 put it in and code is gone but the gear light was still on. Nige(A member here) guided me through some question I had and supplied some pdf schematic. I have owned alot of equipment in 42 years and I have to say that Caterpillar does an exceptional job securing and routing they're wiring harnesses because I checked them all for bad wires looking for this problem to find everything in perfect shape clean, dry, no corrosion or brakes. After running the machine most of this year stuck in one gear 1.5 and full throttle, it occurred to me that the only place a had not looked was in the joy stick. If you pull the button rubber for the shift there is a torx screw in there to split the joystick and access the buttons. Mine was all epoxyed together. When I got it opened, there it was, 1 very tight, to tight, black wire, the ground to the circuit was broken. I soldered some extra length and reattach it, cleaned up the switches. Testing, gear light off and full operation restored. Guys, the local cat dealer would have troubleshot this,$$$$$$ and then replaced the entire joystick assembly at $1500+ just for the part. With troubleshooting, parts, and installation, my guess is 3 to 5 k. My cost, $70 and lots of studying schematics and thinking. So basically I paid $70 for an education. Those 2 buttons on the joystick are more involved in the circuit than you would imagine. Don't discount them, if there is a failure in 1, or the wires, or the circuit is not complete it will throw the gear light,on and you wont shift. Cat is really brilliant in there design but it can be difficult to troubleshoot if your just the owner. Hope this helps someone.
An excellent example of troubleshooting using a forum and your knowledge. Many, unlike you, after troubleshooting do not want to write about it here or are too lazy to do it)
Thank you for the compliment. People can spend hours and days searching for a answer to a problem, and sometimes its there's a step you might have missed. It's a real bummer when a thread just dead ends without a resolution, you see that the thread is 5+years old and all the players are vapor. So to not be that guy I always come back and try to give the end results, good or bad and any costly mistakes I've made. If people would do that for me I would greatly appreciate it. This forum and Nige took the time to help me, that's the least I can do to help others who are about to spend thousands on a problem that, if the knowledge is written, it can be easily and cheaply solved.
It's the bane of this forum's life. People come here asking for help, get it, and never think to come back to inform the members what the final fix was.