I have a 65 coupe with a 289 .30 bored over. It now has a new T5 trans. Most everything in the engine has been replaced/upgraded. I am looking to get new gears. What size do you guys recommend ? I would still like to be able to do 90 on the highway but i would like the gearing to be as aggressive as possible

 

Check this out.

http://www.5speedtransmissions.com/gear_calculator.html

You'll need to know how tall your tires are as well, they act as another "gear" to factor into your ratios.

I run a TKO600 and I have ~25" tires with 3.89 rear end. I run 80mph at around 3200rpm. I think I can do 60 at around 2400rpms...I don't drive 60 often.

James

 

I have the cobra spec t5 with the .63OD and 25" tall tire
I run 3.80 and drive freeway every day. At 90mph I turn 2900 rpm. If I had a normal t5 with a .65OD it would be 3000 RPM @ 90

with numbers like this I would feel bad to recommend anything taller like a 3.55. Ive been running 3.80s daily for the last 6 years and I never said "I wish I had 3.55s right now" But I do find myself saying "I wish I had 4.11 right now"

I do think you would be quite happy with a 3.80

-Gun

 

HA!! Agreed.. I run 3.70's and have often said I wish i had some 4.11's.