What speedometer gear do I need?

[WH23G3G]

I'm going to be using 225/70/14 tires on standard steel 14x6 wheels. I have a 727 and a 8.75 with a 3.91 gear. The year one catalog shows a speedometer gear for 3.91 gears and 205/70/14's but no 225/70/14s. Is the speedometer gear for 3.91 with 225/70/14s going to be hard to find?

[maxwellwedge]

If there is no or not too much difference in the tire diameters you should be fine.

[Ronnman]

The closest I calculated is that you need a 39 (38.83) tooth gear for the 225/70/14 tires.  There is about a 3 MPH difference (about 60 MPH) between 205 and 225 tires.  You should check eBay for the speedo gear or a Dealer.  Also, it depends on how close the existing gear is now.

Ron

[oldcarnut]

http://www.miata.net/garage/tirecalc.html
http://www.geocities.com/MotorCity/2398/tires/tire1.htm

Here's a couple of reference links and calculators for you to check out.  hope it helps
David

[Beer]

Cope Racing has the gears, if you need a price check vs Yearone. 

https://www.coperacingtrans.com/index.php?cPath=69&osCsid=372554591a41d57873af9dcc5682a4aa

Damn looks like we crossed over to the $75 verses the $20 ones with the 3.91's