Speedometer Gear
Thread Starter
Instructor
Joined: Jul 2010
Posts: 103
Likes: 1
Speedometer Gear
The age old question here.....sorry but I've been confused by several of the posts plus what I've read online.
I have a 73 4sp and the speedometer reads 45 MPH when I pass through a roadside radar that clocks me at 35. I realize that they're not 100% accurate but I'm pretty consistently in that range when I pass through any of them in town.
My speedometer gear is a (white) 19 tooth and I've read that each additional tooth will slow down your speedometer by approximately 5 mph which seems to indicate that I need a 21 tooth.
The prior owner removed the stock wheels and installed 255-45R-17's which are roughly 25 1/2" in diameter. Can anyone confirm the number of teeth?
thanks
Jim
I have a 73 4sp and the speedometer reads 45 MPH when I pass through a roadside radar that clocks me at 35. I realize that they're not 100% accurate but I'm pretty consistently in that range when I pass through any of them in town.
My speedometer gear is a (white) 19 tooth and I've read that each additional tooth will slow down your speedometer by approximately 5 mph which seems to indicate that I need a 21 tooth.
The prior owner removed the stock wheels and installed 255-45R-17's which are roughly 25 1/2" in diameter. Can anyone confirm the number of teeth?
thanks
Jim
Instructor
Joined: Sep 2010
Posts: 229
Likes: 1
From: Grants Pass Oregon
[QUOTE=jtramont;1576789647]The age old question here.....sorry but I've been confused by several of the posts plus what I've read online.
I have a 73 4sp and the speedometer reads 45 MPH when I pass through a roadside radar that clocks me at 35. I realize that they're not 100% accurate but I'm pretty consistently in that range when I pass through any of them in town.
My speedometer gear is a (white) 19 tooth and I've read that each additional tooth will slow down your speedometer by approximately 5 mph which seems to indicate that I need a 21 tooth.
The prior owner removed the stock wheels and installed 255-45R-17's which are roughly 25 1/2" in diameter. Can anyone confirm the number of teeth?
Try this web.site I got mine from here. www.redrider.us/speedometer_gears.htm
I have a 73 4sp and the speedometer reads 45 MPH when I pass through a roadside radar that clocks me at 35. I realize that they're not 100% accurate but I'm pretty consistently in that range when I pass through any of them in town.
My speedometer gear is a (white) 19 tooth and I've read that each additional tooth will slow down your speedometer by approximately 5 mph which seems to indicate that I need a 21 tooth.
The prior owner removed the stock wheels and installed 255-45R-17's which are roughly 25 1/2" in diameter. Can anyone confirm the number of teeth?
Try this web.site I got mine from here. www.redrider.us/speedometer_gears.htm
Melting Slicks
Joined: Jul 1999
Posts: 3,030
Likes: 17
From: White Pine / Dandridge TN
One of the things you did not mention that is important is your rear diff gearing. I have a 3.55 with 17" tires and when I called I was told to get the red gear.. not sure of the teeth count but they said the red one was for 3.55 rear and my 17" tire size.
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 330
From: Indy Indiana
Those driven gears are fairly cheap, so buy a 20,21,and a 22 and just try them. its a quick swap out.
my speedo is a little fast with one and a little slow with another. so I can't get it exact..
(assuming my GPS is correct too!)
my speedo is a little fast with one and a little slow with another. so I can't get it exact..
(assuming my GPS is correct too!)
