i have a 1992 Trans Am with the 5.0 TPI
i drive it daily and lately while going at slow speeds my speedometer needle would bounce around. i did some searching and saw that it could be the speed sensor on the transmission. changed that out with the matching D8I part from AutoZone and the speedometer would act a little sluggish at anything below 50, then from 60 and up it would act crazy and then just stop working. so i switched it out for another one from AutoZone and now it doesn't work at all.
Is there a way to tell that the speed sensor it sending a signal (I would guess hook it up to a drill and put a volt or amp meter on the connection)
i only went with the AutoZone sensor because it was $30 cheaper than all the other part stores.
I am about to go try another sensor from another parts store to see if that works.

 

Check your Ground wires,my Cavalier did the same thing,it was a broken ground wire.

 

the ground wire on the speed sensor or the speedometer?

 

On my Cavalier,their was a sm. ground wire coming off the lg. ground wire that goes to the Battery.I'm not sure if you have that type setup at the battery.

 

My 86 has it,so yours probably has it too.Check it for rust and corrosion

 

well turns out i installed the wrong speed sensor
i put one in for the D8I option when my car has the D8N option
i just picked up the right one from NAPA tonight and will install it tomorrow
i hope having the wrong sensor in doesn't ruin anything

 

I am having the same issue with my '92 T/A. Did replacing the VSS correct the issue?

 

yes it did, just make sure you get the correct one. you will have to go off the code in your RPO sticker to make sure you get the right one