I have replaced by rear left indicator light and it still doesn't work! the rear lights still work and the right indicator does. Dont no what to do!Any help anyone?

You will be needing a good electric meter.
With the key on and the turn signal activated, test the leads inside the light socket and see if electricity is getting to the bulb.
When you mentioned it flashes really fast, that says one of the bulbs is not working.
Although it could be burned out, it could also not be making contact, or the ground wire could be bad.
Since the early '80's, cars and trucks have had separate ground wires to each and every bulb and electrical component, and a bad ground will cause this problem also.
Remember, a bulb can look good and still be no good.
God bless your efforts.

flasher/blinker is busted. this is located under your dash board. remove steering column cover, turn on LEFT turn signal (yes, the one that is working), then you will hear a clicking sound. locate the relay that causes the sound. there you can see 2 relays (one for LEFT, other one for RIGHT turn),replace busted one.

One of your bulbs is out. Turn your flashers on and walk around your vehicle to see witch one it is and replace it.

If the red brake light and the ABS light are both lit up on the dashboard, do NOT drive the vehicle. It indicates a major malfuntion with the brake system. The red light indicates low brake fluid or the parking brake engaged. The yellow ABS without the red light, indicates a problem the computer found and it disables the ABS system while still having conventional brakes. Since both are lit, it needs the brake system repaired. What you replaced on the rear diff was probably the rear ABS sensor. The vehicle speed sensor for the speedometer should be located on the rear of your transfer case if you have 4WD, or on the rear of the trans if you have 2WD.

Check for power at the light socket aswell as grounds

Light fixtures are bad check with a light tester

This is a tough one with out being able to see the wiring. i will enclose a wiring diagram for the complete lighting system.
You will need to locate the correct wirng and make sure its going to the correct light. Most times a bad ground wire will make the light do funny things like your car is doing. With the diagram i enclose locate the ground wire to the rear lights and make sure ground is good, even if you must cut old ground out and run a new ground to a good metal ground.

Hello, this indicates a problem with either the left rear bulb or the socket that the bulb goes into. remove the rear bulb and check, also take a good look at where the bulb plugs into the socket and make sure there are no corrosion or burn marks

The problem is the socket. Remove the bulb and bend the tabs in the socket so they make contact with the bulb. If this doesn't work you will have to replace the socket. A wire is broke and they usually break at or in the plug.

check and replace the bulb in the rear left light, the fast blink is normal when the front or rear bulb is out, the brake light not working indicates which one is out