My speedometer cable was shot, couldn't turn the needle. Replaced it, was able to hook it up to the dash cluster, turned it right to left and speedo hand worked. Hooked it up to Trans housing and it didn't work. I'm sure the inside gear is shot, probably the teeth or housing too. How many teeth on the plastic gear part? Its aqua blue in color. There are so many choices. Thanks a ton for any help

 

What gearbox it has?

 

Don't know. Obviously 350 trans, I believe researching a 2.73 ratio. I'm not a mechanic so that is just what I've read. All the plastic gears for housing have so many teeth number variations.

 

Without me having your car service manual at hand, which would have the combinations listed, its hard to say what combination you should have. Different tire-size than original and/or swapped rear-gears also affect the reading. But if its all stock, just put back same coloured gears than old ones. You can also count the number of tooths if you aint sure of colour.

Also you need to know is your drive ( = gear which turns driven gear, which spins the cable), or driven gear shot, or maybe both? Swapping drive-gear for new requires removing tailshaft of the trans ( from my memory, dont have repairbook at hand now).
Driven gear instead is on side of it, and is easier swap. Googling TH350 speedo gears gives plenty of options for ordering them.