Choosing a correct speedo gear.

[fastmonkeywheels]

Okay, I'm getting a little confused here, so I'm posting. Maybe I'm searching the wrong words who knows.

Okay, my new 8.8 rear end has 3.55 gears and I'm running 235/45ZR17 tires with a diameter of 25.32. My T5 is a World Class from a 91 2.3L Mustang so it should have the 7 tooth rear gear. My speedo gear is assumed factory but I didn't count it. I have $50 on it being stock though.

In 5th gear at 2500RPM's I'm doing 75mph, so the speedo says. I know this to be way too fast since I'm getting passed at those speeds in a 60, lol.

I don't know what my 5th gear ratio is, I know I found the information before but I'll keep looking. Does anyone know the calculator to get the correct toothed gear by the information provided?

[BrianO]

those tires and gears... 2500 in 5th you should be doing 67mph. Fifth gear is .79

[NavySVO]

I googled speedometer gear calculator. Some of it is redundant, but the mindspring link talks about T5 gears as well. HTH

http://www.bgsoflex.com/speedo1.html

http://www.tciauto.com/Products/TechInfo/speedo_gears.asp

http://www.sccoa.com/faq/speedgr.html

http://www.mindspring.com/~steveflyer/speedo_gear_select.htm

[fastmonkeywheels]

That' mindspring site is perfect. Looks like I need a 19.793 if I do indeed have the 7 tooth rear gear. Hmm. I thought I would have had a 19 tooth speedo gear factory. Okay, I better crawl underneath and double check before I buy anything.

[fastmonkeywheels]

Yeah, I don't remember if mine was a dark blue or a green though.

[svono50]

That' mindspring site is perfect. Looks like I need a 19.793 if I do indeed have the 7 tooth rear gear. Hmm. I thought I would have had a 19 tooth speedo gear factory. Okay, I better crawl underneath and double check before I buy anything.

The numbers put you closer to a 20-tooth gear than a 19. I would suggest going with the 20. There will always be some error, your task is to minimize it.

[fastmonkeywheels]

Yeah, I know, but I was hoping that I could error in the side of too slow, not too fast, lol. I'll double check what I have tonight and go from there.