Hi all, I have a 1985 TA with an 85 MPH speedo. Can I upgrade to a Firebird 140 MPH gauge cluster? If so, what do I need to do so that it will work correctly?

 

Yours is the most difficult to swap as the speedo is cable driven and most of the 140mph speedos are electronic. Also, has to be a V8 cluster. You will need to find an earlier cluster w/ cable or get one of the signal converter systems to make yours work with an electronic later guage.
search in electrical section and you will find lots of info on this.

 

I got this off fleebay a while back. Its cable driven, in my 84 TA. At the time this was the cheapest and best way to go for me. Just removed old speedo and scerwed in new one.

 

Hi all, thanks for the info.
The main reason I was wanting to do this is because I want to do a T-56 transmission conversion in the future and I read somewhere on these forums that you needed an electric gauge cluster (like the ones in the later model trans am's) to connect to the transmission.

 

Yes, the t56 is electric speedo. I will be putting a T56 in mine this summer. I'm doing the conversion from electric to cable on mine. You will have to run the wireing from trans to speedo.

 

Your 85 should have an electronic speedometer, 82-84 had mechanical. Camaros had mechanical ones from 82-89, not true for the firebirds, though.

 

All you need is to find one of the yellow VSS buffer boxes in the junkyard from an electric speedo equipped car, it's wire connectors, and the correct toothed speed sensor gear and sensor for your new transmission. The gear will need to be found based on this formula: (your tire diameter in inches x rear end gear ratio x number of driven teeth in your trans tail shaft) / 1001. This will give you the number of teeth needed for your speed sensor gear. The formula is also available in many places online, as well as calculators where you can plug the info in and it will calculate for you. The buffer box is pretty easy to wire, and the walkthrough is availble in the tech forums. I did this mod to my originally mechanical speedo equipped '83 Z/28 Camaro, and it worked great. I had upgraded to an '86 Firebird GTA interior and gauges in my Z/28, with the 140mph speedo. I recently used the same buffer box to adapt to my new '94 Camaro speedo, and at all speeds the deviation is less than 1/10th mph, without the use of a factory ECM for the VSS signal (I'm running Megasquirt I which has no VSS input).

 

The t56 doesn't use gears. Neither do any of the factory electronic VSSs. They use a reluctor ring. They're output is always the same and the ecm or buffer box modifies the signal.

85 was still cable in birds. Same with 86. 87 was the first year of electronic.

 

Are there instructions on here for how to do this and what parts to look for? I couldn't find any firebird specific threads on this topic.

 

As far as wireing the T56 to electronic speedo I have not done it, so I can't help you there. As for converting the T56 to cable driven speedo there are several guy's that do it for around $350.00. I'm doing mine myself. If you google it you will find instructions and where to get needed parts.

 

Thanks for all your help. I found some good information on doing the swap with what looks like detailed instructions (haven't read it completely yet) on how to swap the cable driven cluster to an electronic cluster.
Here is the site http://www.hioutput.com/tech/speedo.html

 

The factory electronic VSS does use a plastic gear driven by a plastic worm gear in the tail shaft of the transmission. The gear spins the sensor, which creates a sine wave output that is clipped into a square wave by the buffer box, as well as splitting the signal for both the gauge and cruise control. Without the properly calculated number of gear teeth, your speedo won't read accurately. I've wired this setup on my car with a 700R4, bypassing the ECM (since I'm running a Megasquirt). I can't speak for the T56 manual tranny, but the factory setup for the 700R4 is a plastic gear on a sensor.

 

Where did that speedo come from I would Love a cable driven 140mph speedo in my 1984 trans am

 

Go here they have them.

http://www.youngsfbody.com/8292camarodashvents

 

hey all i have the 120 mph cluster in my 89, can i just swap gauges, and i heard mine was electronic, but i swear at low speeds i can hear the speedo cable, or something else no idea what it would be, sounds like a winding noise 0_o