ok so I a 03 ext cab silverado with a 4.8 fbo and tuned I need to know what gears to go with I have 3.42 right now its my daily truck it has 275/55/20 and they weigh 75 lb each never gonna take it to the track just think I need to upgrade the gears thanks in advance

 

That lil 4.8 could use the torque from the 4.10s either gearset would be a massive improvement on your current setup.

 

tttttt

 

3.90 VS 4.10 is such a small difference it won't matter which you pick.

 

4.10s maybe even 4.30s. The little 4.8 it can use all the help it can get.

 

then why do they say 410 are only good for bottom end and 390 are good for both

 

Who said that? 4.10s are going to be good for you throughout your powerband but your highway mpgs will suffer due to increased rpm. I would just get the 4.10s if it were my ride. A lot of guys go even lower, with 4.30s and 4.56s. It depends on what you're doing with it. I think you'd be happy with 4.10s.

 

If I were to change gears I would get the 4.10s.

 

its just a daily driver

 

Honestly, unless you'll save quite a bit of cash by getting 3.90s, you should just get the 4.10s. They'll give you exactly what you're looking for.