I've only gotten to drive my car maybe a total of 30 miles since buying it and having to get my transmission rebuilt right away. But the speedometer worked and was dead on until the other day when I went to drive it I got a block from my house and when going up to 25mph it suddenly started bouncing around and then dropped to zero and remained there.
So I've done a lot of thread searching thinking its the vss or the buffer box or the wiring someone in between. Well after fixing a broken ground wire in the harness near the firewall I decided to give it a quick spin and see if it made any difference cause other than finding that I'm at a loss on why it isn't working. Well anyways thats when I noticed that my odometer and tripometer DO work. So now that has me because it always seems when I search the threads on speedometer not working the odometer is also dead... also I don't seem to have any loss of power or anything that would be expected with a bad vss or buffer the car is starting and running well and shifting fine. So now I'm wondering since its electric no cable or anything turning the needle how exactly does the needle move? For the most part its always staying at zero but every once in a while it does wiggle up and bounce likes its trying to work. Usually after I come to a complete stop and start moving again.
Should I open up the Gauge cluster is it possible my vss, buffer, and wiring are all fine and there is just something wrong with whatever it is inside the gauge that moves the needle? Please help I've spent way way more time working on my car than I have actually driving it and getting very frustrated. Thanks in advance to all who read all of this and can give me their thoughts on the matter

 

Think maybe I made my post to convoluted? Biggest thing I'm hoping for is confirmation that since my speedometer gauge's odometer is working even though the speedo isn't... Does this mean that the vss is sending the proper signal to the gauge cluster? My reasoning being that if it wasn't then the ecm and gauges would have no idea the car was moving as its all electrical.
Is that logic sound? Could it be just the speedo needle itself which is apparently moved by reflected infrared light and a photocell or something like that?
Really wanting to be sure on it as I think it may be hard to track down a working 87 GTA Guage cluster with the 140mph etc

 

I just fixed another one of these cluster a few day ago. I am located in NY