I just purchased a low milage LS4 engine, transmission, computer, wiring harness, Body control module, etc. From a 2006 Impala SS. To go in my 1987 GT. I have the engine, transmission, and cradle out of the car. Photos soon to follow. So now for the questions.

Question #1. Will this transmission drive my speedometer (with an adapter obviosly)? Or is this a serial bus setup?

Question #2. If the answer to question #1 is no it will not run the speedometer. Is there a engine management system that will and work with the ls4 transmission? Maybe the 5.3 truck engine computer and wiring harness or maybe the fbody computer and wiring harness and disable the displacement on demand. I know this swap has been done so what has everyone else done.

Question #3. What has everyone done for axles?

Thats all for now.

quote Originally posted by Monsterfiero: I just purchased a low milage LS4 engine, transmission, computer, wiring harness, Body control module, etc. From a 2006 Impala SS. To go in my 1987 GT. I have the engine, transmission, and cradle out of the car. Photos soon to follow. So now for the questions. Question #1. Will this transmission drive my speedometer (with an adapter obviosly)? Or is this a serial bus setup? Question #2. If the answer to question #1 is no it will not run the speedometer. Is there a engine management system that will and work with the ls4 transmission? Maybe the 5.3 truck engine computer and wiring harness or maybe the fbody computer and wiring harness and disable the displacement on demand. I know this swap has been done so what has everyone else done. Question #3. What has everyone done for axles? Thats all for now.

Here is all the information you need to know.

https://www.fiero.nl/forum/Forum2/HTML/086013.html

Darth made this swap alot easier to a point by taking lots of pictures and explaining everything.

The ECM/TCM is reprogrammed so the motor/trans will run off it in the Fiero without needing any other support. If you are not adding any features from the MC then you will not need the BCM, which is a good thing.

I am in the slow process of doing an LS4 swap myself from an 06 MC SS. I have the engine mounted, test fitted and the belt routing worked out. I will be starting on the axles next week sometime and hopefully the wiring will be done soon.

Thanks for the response. I found the answers to my questions on Ryans build thread. I was going to change the dash out anyway so what better time than now! I'm going to try to use a 2006 Pontiac GTO dash I have laying around. I think that the computer and harness from that car should work just fine. I measured the dash and I think it will fit. Matter of fact I have the seats, door panels and all from this car. Thats all for now.

your OP contains an immediate error anyway. The new computer will send the speedometer it's signal, no problem there. I doubt you'll use the SS tire size, so you will have to get that corrected when you get the VATS removed. Forget the truck computer. The computer you have is best, and is what your new transmission sends it's VSS output to.
If done right, this swap should be easy to get inspected anywhere except Cali.