Speedometer gear on an 84 grand prix

[84Bushing]

Bought an 84 grand prix and the speedometer doesn't work. It is a 3.8L V6 automatic with what I believe is the thm200c mv9 transmission but I may be mistaken. Im trying to take out the speedo driven gear housing and inspecting and/or replacing the driven gear. Anyone know how I could remove this because the housing isn't moving when I try to twist it with pliers.

 

[Ribbedroof]

Did you remove the bolt and lock tab?

 

[84Bushing]

Yes I did

Did you remove the bolt and lock tab?

 

[timo22]

Sometimes the rubber seal freezes to the housing. Put a plastic lid and use some channel locks . May need to rock it and twist it too.
Seen it plenty of times …
timo22

 

[69hurstolds]

To state the obvious, protect those threads on the sleeve (bullet) when using "assistance" from pliers. If the threads get damaged beyond repair, then you'll need to buy a new one. That'll mess up a $20 bill. Steel and aluminum don't get along well when left alone for years. I know when GM sold the speedo gear for the VIN 9, MW9 with 3.73 rear gears, they used to come as an assembly. You got the bullet and the gear in one shot. Says so in the "note" on top of the '85 gear selection chart in the parts books.

If I were going to bet, I'm betting the gear hole where the speedo cable goes into has cracked, spread, and worn to the point the gear may be spinning in place over the cable. Gotta watch out for changes as well. The 1st design 1984 gears for the Hurst/Olds, for example, had a plastic shaft and were sold separate of the bullet, where 2nd design ones (25524925 for VIN 9) had steel shafts and came with the bullet. Typically, gears don't wear away that often unless there's a million miles on it. It might be a good time to consider replacing the speedo cable as well.

 

[Bonnewagon]

Once you get it out any damage will be obvious. Replace with the same exact part. Don't go by the color as some change with age and heat. Some aftermarket gears are the wrong color. Count the teeth and be sure what you have.