Speedometer gear

[LannyL81]

I replaced the speedo gear with a different one because my 85 turned into a 140 mph speedo was reading about 6-8 mph slow. But I guess I went the wrong direction as now it is 12-15 mph slow. Somewhere I saw a color chart with number of teeth for speedo gears.....anyone know where this was at? Or can tell me which one to get?

LannyL81

 

[JonM]

http://www.novaresource.org/speedo.htm

 

[LannyL81]

Which way to go??

I have had the speedo rebuilt and calibrated at a local shop. But still am about 5mph slow. Anyone know which way to go on the speedo drive gear to correct this?
Seems to me that I need to increase the teeth on the gear, but before I go swaping gears thought I would ask. I have 17, 19 and 21 teeth gears with the 21 presently installed.

Thanks,
LannyL81

 

[GerryLP]

I have had the speedo rebuilt and calibrated at a local shop. But still am about 5mph slow. Anyone know which way to go on the speedo drive gear to correct this?
Seems to me that I need to increase the teeth on the gear, but before I go swaping gears thought I would ask. I have 17, 19 and 21 teeth gears with the 21 presently installed.

Thanks,
LannyL81

Lanny,

IAW the Corvette Central catalog, the note at the bottom of the speedometer drive gear selection table says: "If your speedometer reads too high, a drive gear with one more tooth will slow it down approximately 5 MPH."

The speedometer driven gear should work the same way.

I guess that your car has a manual transmission? Is it like on automatic tranny where one has to remove the tail cone to gain access to the drive gear?

GerryLP:cool

 

[LannyL81]

Lanny,

IAW the Corvette Central catalog, the note at the bottom of the speedometer drive gear selection table says: "If your speedometer reads too high, a drive gear with one more tooth will slow it down approximately 5 MPH."

The speedometer driven gear should work the same way.

I guess that your car has a manual transmission? Is it like on automatic tranny where one has to remove the tail cone to gain access to the drive gear?

GerryLP:cool

Hey Gerry,
Yep, I have a 4sp in my '81. Changing out the speedo gear is very easy. Takes about 20 minutes to do. Speedo gear is on the side of the trans.

And using the guidelines above, since mine is reading slow..I'll drop a tooth on the speedo gear. Well I am going to drop 2 teeth as that is the gear that I have and the original one that come with the car.

Thanks,
LannyL81