I was on the highway after leaving the track, and a buddy of him was reving his engine. He has a 2008 Sierra single cab FBO tuned and he smoked me in a 70 roll. My truck has 4.56 gears, I was thinking a 3.73 would be perfect for track and street. Any suggestions?

 

simple. you're not geared for a 70 roll. if you hook at a dig, you'd probably smoke him. 3.73/4.10 seems to be the best all round gears for 26-30" tires.

 

At the moment I'm running 265/70/17 but I'm planning to buy some 275/45/20 for larger rims.

 

3.73/4.10 are best all around. Also the stall torque ratio of your converter cam effect top end. I have a 4000 hard hit and it pulls less up top then my old 3200, however on a dig or from low mph it hits and also has a better shift extension between gears. I raced an SRT4 neon from 50mph and pulled a car length. Next stop light on a 10 roll I pulled 6 cars. With your gears you will have the same result I would say.

 

So a 3.73 should be perfect for track and street or would it make my truck sluggish at the launch with the cam/stall?

 

Really needs to match the torque curve of your cam so its a compromise but that's a pretty healthy stall. I had 4.10s with a 4l60 and 32" tire and loved it on the highway or from a dig. Also 3.90s with a 31" tire on another truck and 3.73s and 29.5" on another. 4.10s and 28" a bit much. Seemed to be the sweet spot for all around driving for me. Good mileage, cruise rpm and 60'.

 

4.10 and 28" tires is my preference. tried 4.30 with 28" tires too. 32"+ tires are into the 4.56 territory for me. fixing to put a 4.56 on my 33" tires in a 32ooisl lb car.

 

So I'm planning to get 29 inch wheels for daily driving but 25 inche wheels for the track, would the 3.90 be perfect for this? What do you guys think?

 

Tires*

 

Nothing wrong with 456 gears on highway as long as motor can rev

Information these days on these sites are hard to swallow at times