t-5 speedo gear...23 tooth vs 18 tooth

[danewers]

i have a '67 with a t-5 with the stock rearend, my guess its a 3.00:1 or somewhere around there. i got a 23 tooth speedo gear that is made for a 3.55 rearend. with the new gear, my speedo reads 50mph when im going about 70mph. i want to try another gear but im not sure if i should go with a 20 tooth or an 18 tooth? the speedo is way off so i was thinking an 18 tooth might get it close enough. i'm just trying to get it close for now, doesnt have to be perfect. i'll be using the 23 tooth speedo gear when i swap out my rearend for a 3.55, so it wasnt a waste. what speedo gears are you guys using for your t-5's with a stock rearend? any help would be great! thanks!

 

[danewers]

i have stock tires too

 

[stangman67]

Try this: http://www.hanlonmotorsports.com/t5speedo.asp
You need to know what drive gear is in the trans, and look on the rearend housing for the ratio. Its probably 2.79:1. Look in the trans where the cable goes in, the color of the gear will tell you if it's 6 (black), 7 (yellow), or 8 (green) tooth drive gear.

 

[danewers]

sweet thanks! it turns out i need a 16 tooth speedo gear, but the only problem is, i cant find one anywhere! i'd like to avoid getting one from the dealership if possible. any ideas where i could find one?

 

[6Stang7]

NPD has them. it's a blue tooth, part # 17271-2.