Well it's hard to find good shape used "grid" style TA lights. I picked up a set of the regular or formula tail lights. I had a hard time coming up with help in one spot on the forum here so I decided to do a write up. My project was putting lights from a 91 formula into a 85 trans am. Basically going from the 4 wire lights to a 5 wire light.

Make sure to grab the harness from the donor car. We then cut off the original harness connector and soldered it on to the new harness. Just match up the colors. Note that the blue wire from the lights has no spot to go in. On the car side of the harness remove the light blue wire. The dark blue and light blue wires need to be connected together.

Note: From what I see all cars have the light blue wire run. On Trans Ams and GTAs it is a dead wire though. We will get to that in a bit.

 

Here is another pic of the connector at the back of the car by the driver tail light.

 

Ok now for some work under the dash. First thing to do is to find the brake switch. It is pretty easy to find. The one connector has an orange wire coming in (12+ constant wire) and when the pedal is pressed it allows electricity to flow out the white wire (turning on the brake lights) Now at this point if you press the brake pedal the blinkers will actually both turn on, thats no good. You will need to cut the white wire as far away as you can from the connector.

Now to find the other end of the light blue wire from the back. The tail light wires are in a plastic sleeve from the back of the car all the way to the driver side kick panel. This makes it pretty easy to follow and it goes to the very far back corner connector. You'll see the light blue wire connected but if you look at the other side the pin is empty. Cut the light blue wire off.

Now you will need to connect the white brake switch wire to the light blue wire. Voila the brake lights work but there is one more step.

 

Here is a pic of the connector in the kick panel. The dark blue wire is my jumper wire from the brake switch. Can't really see the light blue wire but it's in that connector. If a person wanted to you could run your own wire from the white brake wire all the way back to the blue wire in the tail light harness.

 

Ok now the last step. If you've been playing with your lights at all you might have noticed that the turn signals don't flash. Not sure why but the original flasher won't work. I used a 552 hazard flasher from another junk car. Simply remove the YELLOW flasher (it's hidden more so than the metal hazard flasher) and replace it with the different flasher. Both flashers are located to the right of the steering column under the dash in what the chilton books calls the convenience center. It does unlatch and swing down. Once replaced the turn signals will flash properly.

Note: In the picture I have the new flasher installed and i'm holding the old flasher that won't work.

 

Any idea how to do the opposite ? I'm trying to swap an 87 tail light harness with an 84

 

I am not sure why this guy went through all that trouble. I did something similar and got it to work without all that splicing. All the re-wiring needs to be done on the tail light harness. I could help you out when I get home and look at the factory schematics

 

Alright, thanks