Speedo gear questions - yes I did a search

First question: I have a 4R70W from a 2000 3.8L in my splitport tbird, does it have the 7 tooth speedo drive gear or 8 tooth? I've been told both, so which is it?

Second question: If it is a 7 tooth (I hope it is), should I use the 19 tooth or the 20 tooth? The gear selector says 19.5.

Thrid question: If it is an 8 tooth drive gear, who makes a 22 tooth speedo gear? Does Ford make one? I've heard something about a Chrysler one, but I did a search and didn't come up with anything.

By the way, here's the current setup:

255x60-15 rear tires (27.04" tall)
4R70W from 2000 3.8L Mustang
3.73 FRPP centersection

Thanks,
Rod

Rod, the Ford parts catalogue shows the 00 Mustang 4R70W as having the 8 tooth gear on the output shaft.

The highest tooth count for a driven gear from Ford is a 21 tooth. Through Chrysler, I know that you can order a 23 tooth gear nder a Jeep #, but it is the shorter manual trans. style gear. P/N is J3167393 ... not sure if they also have a 22 tooth application as well or not.


cheers
Ed Nicholson
SCCoO

Thanks Ed,

One more question, with my current setup, how far off do you think the speedo would be if I just went with the 21 tooth? The speedo gear calculator recommends a 22.3 tooth. Would that just mean that it would be off by 6% (100 - 21/22.3)? How noticeable would that be? If it's only 6%, that would mean that the speedo would read 64 MPH when I'm going 60 MPH, right? I think I could live with that.