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Old 09/17/2022, 12:13 PM   #1
Tequila
 

Location: Seattle WA
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Speedometer gear teeth

Hello,
I have a 3.40 gear ratio posi-trac rear end with C4 auto transmission. The speedometer MPH hour is way off when driving. For example, the gauge reads about 42 MPH when going at 35 MPH (measured via GPS).

I have the standard C4 transmission speedometer gear in there. I was wondering if anyone could tell me how many teeth are on the original speedo gear, and how many teeth gear should I need to get the speedometer close to actual mph. I am being lazy and don't want to remove the existing one to count the # of teeth. I would rather just order the replacement and swp it at the same time.

I am running on Cooper CS5 Ultra Touring Radial Tire - 225/60R15 tires.

Thank you
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Old 09/21/2022, 06:15 AM   #2
rvrtrash
 
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The driven gear would depend on which rear end ratio and tire size the car had originally. Also, someone may have changed the gear in the past. IIRC, one size, 15 tooth I think, was not available for a while, might still not be available, and a different tooth count might have been used. It's pretty easy to pull the cable out and count the teeth. I think you just need to do that.

The wannabe formerly known as an owner.
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Old 09/21/2022, 08:05 PM   #3
Tequila
 

Location: Seattle WA
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Thank you. Appreciate the help. I will give that a shot.
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Old 09/25/2022, 10:59 AM   #4
robert campbell
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Call Modern Driveline and give them your ratio and rear tire diameter. They will fix you right up!!

Rob

https://www.moderndriveline.com/
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Old 09/27/2022, 01:53 PM   #5
Tequila
 

Location: Seattle WA
Joined: Sep 13
Posts: 338

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Quote:
Originally Posted by robert campbell View Post
Call Modern Driveline and give them your ratio and rear tire diameter. They will fix you right up!!

Rob

https://www.moderndriveline.com/
Thanks Rob. Appreciate the lead. I called and unfortunately they specialize on manual transmissions so they couldn't help me. Anyways, I am hoping to remove the old speedo gear this weekend and look into it.
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