Hello,
Got this car a while ago with a bad transmission (wouldn't shift after warming up for 5 minutes) multiple flushes etc. it sat for 3+ years before I got it because of that issue

Finally replaced the transmission with a junkyard one which has fixed that issue ao far. Speedometer was bouncing all over and then just stayed on 0mph after first 10 seconds of driving with replaced transmission.

Replaced the vss with a cheap ebay one and it never fixed it, I pulled it off to maybe reseat it or check connection, and the little gear on the end of it wasn't even on it anymore, and must be somewhere in the transmission now. Fyi, it's the longer cylinder, 3 terminal sensor with the little gear towards the tip.

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Got an Inport direct brand and it fixed the issue for at least 150 miles / 2 weeks+, until now where it started bouncing around on the gauge, and then goes to 0 after a while.
warrantied the sensor and it did not change the issue at all, so I'm less thinking it's a sensor issue.

It's gotten worse after 2 days of it being like this, where it almost just stays at 0 all the time now, and the car drives real sluggish from a start. Almost like there's no power.
Has the cel for speed sensor range discrepancy or something.

Pulled the sensor and it looks fine, didn't see anything out of place in the transmission, and cleaned the plugs with contact cleaner. Made no difference.

Fuse 15 under dash is not blown (alternator eld fuse).

Not sure what else it would be, now.

Potentially ECU, or actual transmission?
There is a possibility the new warranty sensor is bad too, I guess?

Those were the only areas I could find to check while searching, let me know of anyone has other suggestions.

Thanks! 🙏

 

Finally had some decent time to check it out further today.
Pulled the new warrantied sensor out and spun it with a drill and it worked fine so transmission was thought to be the culprit. Turns out the speed sensor gear sits too low in the transmission to catch the transmission gear, and the speed sensor shaft has vertical play. I'm assuming the first ID I put it just luckily sat at the right height and then shifted down after driving around for a couple weeks, and the warrantied didn't sit at the right height from the get go. Must be a defect with the Import Direct brand speed sensor. Anyways, I have the speed sensor lifted with a washer on the bolt now and it seemed to fix it.

Just in case anyone else is having a problem and they are certain it is sensor related vs contact/electrical/cluster/etc. Check that your sensor's gear on the shaft sits at the right height in the transmission to catch the gear properly. Obviously this only applies to the 3 terminal with a gear on the shaft type sensor (which looking at the stock picture below, is probably where the gear is supposed to sit, but in reality, the shaft pulls down like 1/8-1/4 inch, which causes it to sit too low in the transmission, apparently: