I have a 07 sierra, 4.8 with some bolt ons for now, 3200 stall, 22" wheels with 30" tall tires. I do mostly in town driving with the occasional highway trip to a show. I am looking into 4.10 or 4.30 gears and posi rearend.

Question is 4.10 or 4.30? Right now at 70 I am about 2000rpm

 

4.10 should be more than able to put a smile on your face

 

4.30 since you don't do a lot of highway driving. 4.56 gears would be really fun to drive.

 

I run 4.30's in my daily and really enjoy it. Most of my driving is city and the MPG have not suffered a all. When I highway drive it does take a hit and is irritating. Couldn't imagine 4.56's on the highway with a smaller tire, city I be the results would be the same no real loss in MPG below 50. With 4.30's the gas mileage is good till after 60 then it starts falling drastically every 5 mph increase.

4.10's if you highway drive a lot since I imagine it would be only a slight loss of MPG @ 70-75ish

This is with my LQ9 which really does not get the greatest mileage anyway.

 

4.10's for me and I love them
but if I had to redo them I'd probly go 4.56's, however I have a 6 speed though

 

Why such low gearing with a 6 speed... how short do you want your first gear to be??? lol

 

4.30's would be more fun forsure. I run them and I really like that ratio, but I am also on 33 inch tires

 

my thinking is the diff. between the 2 would be minimal. if you have 3.73 already, skip the 4.10 and go for the 4.30s.(ill be doing this at some point in the future myself) there are some calculators on the web that will let u play with diff. gear ratios to see where your rpms will be at various speeds.

ive seen some posts where guys have swapped gears from 3.42 to 3.73 or 3.73 to 4.10 and ended up a little dissappointed at the results for the amount of money they spent. my buddy was one of these guys, altho this was in his 91' tbi rcsb sport truck. we felt a difference, but not as much as we were expecting. some recommend going down(numerically higher) 2 gear sizes instead of one.

whatever you choose, youll more than likely have a smile on ur face especially since you have heavier 22" rims

 

I have 4.10s with 6 speed, pulls 2100rpms on freeway at 70mph. Drives great with the 3200 stall, made it a bit better in town driving. I would have gone 4.30s if I could have with mine but i couldn't find them for the 10.5". The posi will make you happy as well.