With head lights on, no tail lights. Brake lights

it sounds like you lost ground circuit I believe its a single black wire from circuit board connector to frame One on each side of truck

Yes, if your turn signals in the back use the same filaments as the brakes, the multi-switch must allow the brake signal through when the turn signals are not activated. There are multiple diagrams for your system, so I'm not sure what you have. If you have the light blue wire that goes from the brake switch ul the column to the turn switch, make sure it is getting power when the pedal is pressed. It should go thru the switch as shown in the second diagram below.

a bad turn signal switch the brake lights go threw the turn signal switch

Yes I would look for a ground circuit problem. I would look at the ground wires for the headlights first. Even run a new ground wire for the tail lights to see if it helps.
Could be a ground connection for the body to frame or body to battery.

The brake light side of the bulbs is powered by the brake switch and travels thru the turn signal switch.
If the third brake light works, I would guess the problem is in the turn signal switch.

If you are very sure the wires are good, then you need to replace the multifunction switch in the steering column. Be sure you have checked the wire harness for bare spots or a broken wire first. Hope this helps.

Sounds like a blown fuse or a ground wire broke.

I've worked on these the first drove me crazy. its the turn signal switch every thing runs thru these. head lights, turn signal, brakes. except the third brake light. it runs directly from the brake switch. go figuare

ck the wire that comes from starter,,see if it didnt rotted off,,

WHAT YOU MIGHT CHECK IS THE FUSE FOR TAILLIGHTS, OR DASH LIGHTS. THEY WORK OFF THE SAME FUSE. IF THE FUSE IS BLOWN THE HEADLIGHTS WORK BUT NO TAIL OR DASH LIGHTS