4.8Silverado'06

How do you think the daily driving MPG's will be effected? I spend more time driving to work then towing. Generally 65 mph for 1hr per day. (thats if I dont drive the little honda gas saver) Just curious. if MPG goes down, it wouldn't be the end of the world, especially if towing is significantly helped. Atomic, as we talked before. Boost is def. were I wanted to go with the truck, but its far out in the future, It just needs some help for now. gears and tuning is probably were I will go with it.

Atomic

iTrader: (42)

Well I can tell you my personal experience with a slightly bigger truck with a 5.3 that was lifted on 35s. With 3.73s I would get roughly 12 to 17mpg depending on the type of driving. Going to 4.56s I would get roughly 14-15mpg no matter what. You will notice the average mpg of both is the same, just with the better gears it didn't vary as much. Long way of saying the mileage was about the same for me. The better news was the truck no longer felt like I was towing a boat all the time.

Bluecollar Hotrods

iTrader: (18)

I just did 4.11s, nice improvement over the factory 3.42s, but I can tell it wants more. I geared it based on the future LQ4/80E swap. If I was staying with the 4.8, I would have done 4.56s or 4.88s.

4.8Silverado'06

currently im running at 2k RPM at 70MPH. Judging by some of the gear ratio charts I reviewed last night, I should raise my RPM by approx. 500 by changing from 3.73 to 4.56. This would put me at 2500 RPM @ 70. This seem like a good rpm range to be in for highway speed? I can imagine the overall feel of driving the truck would get significantly better. Like Atomic said, make it fee like its no longer towing a boat everywhere I go.

Atomic

iTrader: (42)

Yea that will be just fine, especially for towing something. Gotta let the little engine rev!

4.8Silverado'06

is there any worth in doing a cam also? If im going to pay for a tune, may as well get the most out of it i would think... Or is there just not enough gain with a small cam to make it worth the price?

Atomic

iTrader: (42)

You would certainly get more power out of it, but gears will give you the best overall increase.

Just doing some public school math, lets say at 3000rpm your engine makes 250ftlb of torque. If you add a cam lets say that's 270ftlb.

In 3rd gear, 3000rpm, stock cam, 3.73 gears that's: 250*1*3.73=932ftl/lb at the wheel
In 3rd gear, 3000rpm, cam, 3.73 gears that's: 270*1*3.73=1007ft/lb
In 3rd gear, 3000rpm, stock cam, 4.56 gears that's: 250*1*4.56=1140ft/lb
In 3rd gear, 3000rpm, cam, 4.56 gears that's: 270*1*4.56=1231ft/lb

So with some guessing on the numbers a cam will get you 75ft/lb at the wheel while gears will get you 208ft/lb. Almost 3 times better return. To get the same overall effect with a cam you would need a huge cam on that engine with the other mods like headers, intake, and converter to really get it to shine. I don't really think you want to sink $3000 into it to have it drive much worse.

4.8Silverado'06

From the information I am getting from you all, I plan on gearing the truck, open the exhaust up and get a tune. I was just debating doing a cam at the same time to help out even further. Of course, only if the price of the cam was worth the added power. beings that I will be paying for a tune either way, that becomes negligible. So, say I get a cam ($400) does the cam net me enough usable power for the extra $$ ??

Atomic

iTrader: (42)

Its not just the price of the cam to do a swap... say cam is $400, pushrods $100, valve springs $150, coolant $25, oil $40, and free labor (yours), so its actually about $700ish for a cam swap.

I say do the gears, exhaust, and tune and if you are still wanting more then do the cam and have it retuned. Most tuners will do a retune for free with mod changes or at least at a greatly reduced rate.

4.8Silverado'06

Good point. I'll start with gears exhaust and a tune. Thanks for all the input!