My trans was shifting hard and the speedometer would only work at and past 40 mph. I have replaced the trans speed sensor and the shifting seems to be better but my seedometer still will not work untill you reach 40 mph or higher .How or what do I need to do to fix this ?

Trans could be stuck in limp in mood, may just need to replace the speed sensor, or diagnose the no speedo problem.. Trans relies on speed sensor info to shift

Vehicle speed sensor, wheel speed sensor, your VSS operates you MPH and tells the trans how fast you are going and when to shift, it is telling the trans that your not moving so why would it shift? Next your ABS wheel speed sensor tell the car what wheel is moving at what speed to activate traction control and abs systems both are very sensitive and easy to break

I’m happy to assist further over the phone at https://www.6ya.com/expert/brock_d67526d2a834c47e

Fluid Change has nothing at all to do with a fix
Nothing at all & on a worn trans can cause slipping
In your case I assume a shop gave it a try
The hard shifts tell you the valve body needs cleaning
I would first look at all body data related to the trans,whatever
your truck has TCM Module whatever
I would check all bulletins at a repair shop in their data base
I would have a mechanic ride with you to look at the trans
with the scan tool on it & watch the speed sensor & any
external sensors you may have for correct data
No also check the brake switch
Does it go into Lock-up in most gears (brake sw )

The speed sensor that is under the trans. mount on the driver side sends the shift points to the computer telling it at what point to shift. The sensor that actually controls your speedometer is in the back near the firewall. It is tall and should have a silver heat shield over it. However, the problem that you have described sounds more like an electrical short or a wire grounding out somewhere. I would check for wires getting pinched under the steering column in the dash since things quit working when you are turning. Also check the wiring behind the instrument cluster. Elecrical problems can sometimes be complex and hard to find but with some due diligence they can be solved. Hope this helps.

Replace speed sensor on trans

NO, IT'S NOT THE TRANSMISSION! SOUNDS LIKE A SPEEDOMETER PROBLEM! THAT WOULD BE ONE OF THREE THINGS! EITHER THE SPEEDOMETER, THE CABLE, OR THE SPEED SENSOR! THE SPEED SENSOR WILL USUALLY GIVE YOU A P0500 CODE ON AN OBD-II CODE READER! THE SPEED SENSOR IS ELECTRONIC SPEED CONTROL LOCATED ON THE TRANSMISSION! SOME HAVE A SPEEDOMETER CABLE HOOKED TO THEM, AND SOME JUST HAVE A 2 WIRE PLUG THAT HOOKS TO IT!

Double check your work

speed sensor runs all three gages. Sounds like trans might have lose or missing bolts. Get it checked out.

Replace the speed sensor on the trans that will cause exactly what you describe is happening.

Your speed sensor in your trans. needs to be checked out sounds like its not working or not getting a good signal until its generating enough power and speed to start until it reaches 30 MPH. Check that out sometimes it could just be some dirt on it. It all makes sense the ABS light is on because its not reading the speed of the tires, and the AOD light is on because It has no idea when to shift into overdrive without knowing how fast its going. I sure Hope that Helps You Out, And Thanks, Bear001