I have 35 on my truck if I go up in size will that help my gas millage or hurt it?

Would the gears help the profermance?

I am looking in to a set of 4.10.

 

Gears will help your performance and gas mileage. With 35s and stock gears (assuming 3.73s) your very under geared. I wouldn't go with anything less than 4.56s, I ran those with my 01 on 35s and then 37s. The 5.3 has plenty of top end power for you to run 4.56s as a daily driver. Hope this helps, Good Luck!

 

Personally I'd go with the 4.56's simply because 4.30's are not available for your front differential, according to ringpinion.com. I have 4.30's in my rig with 35's and I think it's the perfect compromise between power and highway driving. The Dune Grappler tires are lightweight so you could get away with 4.10's but at the same time it seems as if the direction you're heading with your 5.3L is towards high end power with your shorty headers and "cam on the way", which if you follow 99% of the guys on here, will end up with a camshaft too aggressive for a lifted truck. So, 4.56's.

At 70mph you'll still only cruise at 2150 rpms, vs the 1750-1800 you cruise at now.

 

we did a 4.8L w/35" tires.Installed 4.56 gears. He was more than happy with the performance and fuel mileage.

 

A 4.8L would need 4.56's, preferably 4.88's if he's off-road more than on highway.