The brake lights and turn signals work but the tail lights do not work. Headlights are ok, have checked all fuses and replaced with new fuses. Have followed wiring and all seems to be ok. Not sure how to proceed.

 

Check the fuse box under the hood? oops my bad. Did not see year of truck. Never mind

 

check the brake light activater on the brake pedal under the dash if thats ok check for proper ground and corrosion 2 the taillights themselves also if you got a volt meter and a bud to help have them mash the brake pedal while you check for power at the tail lights housing.............

 

I'm assuming that the lamps aren't burnt out and that there's no power to the sockets? We're talking about the "parking lights?"

This is an '88? Not sure if this will be of any help, but I had an '87 and I had forgotten about a problem until I read this post. Look inside the engine bay, driver's side, firewall. Look for the big wiring harness that's plugged into the firewall. Are any of the wires bare?

My '87 had a problem where the insulation on several of the wires had shrunk back. I ended up sticking tape between the wires just to keep them from touching and shorting out.