Brake light stays on change everything b ut the left wheel sensor mech hook his reader to my truck and code said left front wheel

If you get someone with a fault code reader. A good home mech may have such a thing then read the code and it may give you a hint as to where the problem is. You checked the wheel sensors but how do you know they are OK, you would only know with test equipment?

You will not notice any change in driveability due to ABS sensor. On braking the computer will not be able to control the anti lock system as it can not read the Left front wheel speed. Only time you will hear a woo woo sound if the Wheel bearing goes bad and has play. Otherwise if you plug in a OBD II code reader you will find
Code C0035 for Left front Wheel Sensor Malfunction.
Please read this article at Underhood service.com. link address is:
http://www.underhoodservice.com/wheel-speed-sensor-diagnostics-for-meters-and-scopes/

You need your vehicle checked with a scanner that reads ABS codes. Not all scanners can read ABS codes. Most likely it's an ABS wheel sensor that's bad. I've changed a few of them on 02 & 03 Explorers.

Good luck.

There are 4 wheel sensors for the ABS not 3 and the brake light may be the sensor telling you that the brake fluid in the reservoir is low and needs topping up

left front wheel sensor is not reading replace wheel speed sensor

noise might be transmission,

there are sensors on each front wheel and on the rear axle for reading wheel speed have a diagnostic machine hooked up to find which one is bad most common will be on one of the front wheels

You must hook up a scanner that can read the ABS system to the diagnostic connector under the dash and see what faults codes are present in memory.

try taking battery off for half an hour and retry

Common issue when a wheel sensor gets faulty.On every wheel there is a sensor which informs the ABS system about wheel speed.If any of them is broken then the ABS system locks up and you get the warning light.In this case your brakes are working just as fine but you dont have ABS so wheels can block when you push the brake hard enough.Trouble code reader can tell you which one is faulty.