I have 2008 gmc sierra i replaced breaklight switch now break lights stay on and dont function right

If the right front signal light of your 2010 GMC Sierra stays on even when the truck is shut off, it could be due to a few possible reasons:
1. Stuck Relay: There might be a malfunctioning relay in the turn signal circuit that is causing the right front signal light to remain illuminated. A stuck relay can keep the circuit closed even when the vehicle is turned off. In this case, you may need to have the relay replaced or repaired.
2. Faulty Wiring: It's possible that there is a wiring issue in the turn signal circuit, causing a constant power supply to the right front signal light. This could be due to a short circuit or a damaged wire. Inspecting the wiring harness and connections for any signs of damage or loose connections would be necessary. If a faulty wire is found, it may need to be repaired or replaced.
3. Malfunctioning Switch: The turn signal switch itself could be defective or stuck in the "on" position. This can cause the right front signal light to remain illuminated regardless of the vehicle's status. Replacing the turn signal switch might be necessary if it is determined to be the cause of the issue.
To pinpoint the exact cause and resolve the problem, it is recommended to have a qualified mechanic or an automotive electrician inspect your GMC Sierra. They will have the expertise and necessary tools to diagnose the issue accurately and carry out the required repairs.

check fuse relay wiring and switch and if lighter kept blowing fix dont throw in bigger as you see could have burnt truck down

Follow the brake petal up to the brake rod. Unplug the switch wire then take the clip of the petal then the brake light switch should slide right off.

service the 4x4 change swith on the transfer case

You have not set the switch correctly, at rest the switch is operated and the lights will be on. The switch needs to be set resting on the brake pedal with the plunger depressed, as the pedal is pushed it moves away from the switch, the plunger extends and switches the lights on.

check fuses/light bulb/ light/switch

There's a switch at the top of your brake pedal. They wear out, chance are that's the problem, easy fix in the driveway.

yOU WILL HAVE TO PLACE THE sWITCH IN THE STEARING COLUME IT COST ABOUT 90 DOLLARS.

have you replaced the bulbs?

Sounds like breaklight switch needs ajusted, under dash above break peddel you will see it. should be able to move it back and forth for the right setting.