I have a stock 4.8 in my Yukon, went from 3.42's to 4.11's....get the 4.10's...seriously.

 

Folks really can't comment on gears without knowing the tire size, and trans ratios, if you want to get techical. As the tire gets taller, the effective ratio of the rear diff goes down (like from a 4.10 to a 3.42 for example if going from say a 29" tall tire to a 33" tall tire...not sure if these numbers are accurate, just throwing out an example so you get the idea).

Your tire size is exactly what the SS's run (about 32" IIRC? ), and the SS's come with 4.10's from the factory, with the LQ9 and 65E. IMO, I'd go with the 4.10's...that 4.8 needs all of the help it can get down low, and you'll probably be cruising at less than or around 2k at 65mph on the highway if I were to guess...

 

I forget the difference in overdrive between the 6L80E and his trans, but with 3.73s and a 33" tire I see about 2000rpm on the freeway. With a shorter tire and 4.10s he'll be a little higher. If I were to do a gear swap (especially with the bigger tires I have) I would be getting 4.10s. I agree completely that he should get the 4.10s to give him some of the torque the 4.8 lacks. If it wasn't for highway manners, 4.30s-4.56s would be great, but I doubt he wants to be buzzing around at mid-2000s on the freeway every day I know I don't.

 

4.10s or 4.30s

 

Not to threadjack but I have the 3.42s and do a lot of highway driving... I'm wanting to keep about the same mileage on the highway at about 2000 rpm at 65-70

which would do the best for my 4.8 ecsb? 3:73s , 3:90s or 4:10s
or is the highway mileage not really more than 1 mpg for the 4:10s?

 

hard to determine since we dont know what size tires you have.

 

/\ What he said /\

 

I knew that's what I'd get if I didn't go double check

i have 255/70/R16s

 

dont fear the gear! lol i have 4.10s with a 31 in tire. perfect combo imo def say go for it since the op has a torqeless 4.8