Speedometer and odometer doesn't work all the time, analazer said speed sensor at the transmission, put new one on and still does the same thing. Could it be the instrument cluster or a loose connection?

. Check all under dash and under hood fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-t...tml#post252145

. Check connectors to VSS and instrument cluster.

If problem persists, replace the instrument cluster.

TxGreaseMonkey: I did all this and it didn't help. Whoever had the car before me had the rearend gears changed to racing gears and so there is a speed converter box under the floorshifter. This box went bad. Hope this information may help you later. Thanks for your help.

The Vehicle Speed Sensor (VSS) mounted to the transmission can only calculate the speed at the output of the transmission.
If modifications have been made, compensation for those mods need to also be made to determine road speed.
Failed components that could effect the speedometer readings may well include that converter box.
However, the speedometer still gets it's input from the VSS, unless that was somehow bypassed by mods.
What I'm trying to say is, if you've changed the VSS and the problem persists, you very well may have a problem with the harness or connection, or a problem with the instrument panel cluster (IPC).
Whew!

The vehicle speed sensor wasn't working because the converter box went bad. After replacing the converter box the speedometer and odometer works fine.

Good job.