Hey 3rd Gen community. Need your help on a 1984 Trans Am question. Does this car use a vehicle speed sensor to control the cruise control? Car is a carbed motor. If it does use a VSS, where is it located? Does it also need a VSS buffer module? What about cabling from the transmission to the VSS (if it has one), and then on to the speedometer and cruise control? How does that work?

Your help is greatly appreciated!

 

anyone?

 

The system is vacuum operated. There is a relay upon the to left of the radiaor with a cable coming off of it. Probably hooked on by a bead-chain. This cable runs to the throttle bracket on the carb.

When you activate the cruise, the cruise servo next to the radiator uses the vacuum it senses in the system to sets to the speed and holds the throttle steady via the cable that goes up to the throttle bracket.

I am 90% positive that it uses only the vacuum pressure and not a VSS to sense what speed to hold it at so if you have a vaccum leak, this will cause the system to "hunt" for the correct speed. It will also cause it to surge a bit going up and down hills as the engine works harder/easier in those situations.

 

Also, no VSS that I can find in mine. The speedo cable goes strait from the back of the speedometer to the transmission.

 

I was going to add cruise to one of my Camaros a while back.
There is a cruise control module near the ECU under the dash.
The VSS sensor should be connected to the (mechanical) speedometer with red, black(?), & green wires that lead to a yellow box that then leads to the connection out of the cluster. From what I recall, the ECU, CC module, brake switch and VSS are interconnected with the rest of the CC system.
I suspect that you Firebird is similar.

 

When I looked at the wiring diagrams, I see there is a signal wire from the ECU in the circuit to the cruise harness. I just pulled the dash harness out of a 85 Firebird and it looks almost identical to the 84 T/A circuit. So yes, there is some sort of interconnection between the ECU, the cruise, and brake. But, I didn't see anything that I could positively identify as cruise module. Like OZZ1967 said, the speedo cable runs straight from the cluster to the trans. There is an electrical connection from the trans to the ECU that I assume includes the TCC and OD (top gear) connections.

 

Ok, I located and old post I made that includes images of the system. Some wiring goes to the main harness and were marked as open. Example:

Original post:
https://www.thirdgen.org/forums/post...97-post21.html

Also an Ebay add for the cruise control module for identification purposes.
http://www.ebay.com/itm/1986-PONTIAC...-/300786745724

Here's a link of the VSS sensor that should be on the back of any mechanical speedometer cluster. They call it a filter but the sensor is the black thing on the end.
http://www.ebay.com/itm/85-1985-CAMA...-/220355508401

 

The system in the 84 might be the old style system that was used in the 70's. It is very crude. At least the one in my 82 is.

 

Just did a quick search - 84 and up are different then the 82-83 systems, so the diagram above should apply to the system you have in your car.

 

On all the research I've done on it, I think 84 was the transition year between the old and new systems so it's possible that some models will have the old style and some the new, especially the later in the year 84 models.

 

Looks like pretty much everything, except that box in the center, left in the picture. what do you call that module? BTW, thanks a TON for posting that picture!!

 

Glad to help. I just call it a cruise control module. It should be right next to the ECU.

 

found it right where you said. GM p/n 25031953 on it. Found one listed on eBay too that pretty much confirms what I'm looking for to complete the system.

By the way, I posted this in response to a customer's question. He converted a 1984 T/A from left-hand to right-hand drive (in Australia) and wants to make his cruise control fully functional again. He did an awesome job crafting the conversion.

Thanks very, very much for all your help and input on this.

 

You are very much welcome! I had to learn the hard way when I bought one online and found out that I only received half of what was needed.
That sounds like a cool project and possibly a bit frustrating as well. If he posted the project online please send me a link, I'd like to see it.

 

I've let him know his "fan club" is asking for pictures. He emailed a couple to me. It was a pretty slick conversion. Looked almost factory-installed. Quite an accomplishment. Aussies! Go figure.

 

Guys, I'm in Australia which means we are a Right Hand Drive Country. This means that unless are vehicle is a "classic" i.e. 30 years old or more, it MUST by law be converted to Right Hand Drive before you can drive it on our streets. Even if the car is 30 y.o.+ it's really not all that safe to drive around by yourself especially at intersection when turning right because from the L/H seat you simply cannot see oncoming traffic. Not to mention you need all the suspension adjusted so that it sits flat on the road to allow for the natural road falloff for rain. Of course, you also need to replace the headlamps so that they don't blind oncoming drivers at night. All these little things. Here are some pics of both my 67 Mustang conversion and my 84 TransAm conversion. Yes, each is difficult for various reasons but the plastics in the TransAm dash are very difficult considering the way the instrument cluster butts up against the connectors so if you plastic engineering is just a little bit out, the electricals won't line up and either not work, or worse, they can short out really easily and burn up wires and/or the printed circuit board (which need to be cut in half and re-joined). There is none of this with the Mustang conversions.

 

more pics

 

part 3

 

part 4

 

part 5

 

part 6

 

I'm not really sure what you're asking.

84 is 30 years old starting this fall depending on when yours was built. Don't convert it.

There are guys driving Firebirds and Fiero's all over England without converting them to RHD, just adjusting the headlamps.

I drove mine for 3 years when I was stationed there with the US military and never really had any problems, I just had to make sure I was very clear when passing or turning. Yes, it's difficult, but not hard to overcome.

 

Wow! That is truly amazing. I'm somewhat familiar with how close things are behind the dash as well as the connectors on the cluster, so I can appreciate what you're saying about that. I imagine that reconnecting the electrical was a bit challenging after cutting that cluster in half. That's not mentioning all of the mechanical and other electrical work. You've done a really nice job on both the Trans Am and the Mustang. Thank you for coming here and posting the images.