T5 Speedo Gear

[XXBULLETSXX]

Ok I am just about finished with my C4 to T5 swap. But I've got a question and didn't find the answer when I searched. So I thought I would ask for help.
I have no idea what my rear end gears are but I'm assuming they are stock for a 66 fastback with a C4 (has a Brown/dark red speedo gear). I'm hoping someone here can help me with a best guess.
I've got 17" wheels with 225/45's on them.

Million dollar question:
What speedo gear do I need now?

 

[rbohm]

if the speedo was accurate with the old settup, you can use the same gear and speedo cable with no problem. it should just plug in. but in order to give you the correct driven gear, i would need the rear gear ratio. you can test the speedo to see how far it might be off by driving the car ten miles(a know distance of ten miles. best to use the mile markers on the road). if the speedo is accurate, it should read 10+- 2/10 miles. that is about as close as you will get. if your odometer reads more than the 2/10 mile error, then you need to change the driven gear depending on how far off the odo is, and which way.

 

[jcode68]

I used this site to figure out which speedo gear I needed:

http://www.hanlonmotorsports.com/t5speedo.asp

You will need to know your rear gear ratio, but maybe you can figure that out based on the stock speedo gear color that you have? Google search? Hope it helps.

 

[XXBULLETSXX]

Great! Thanks for the help!