SimpleGreen

So I bought an '05 Silverado a couple months back. Its a 2WD crew cab. Tires measure 31" tall. Maybe a hair more. Truck has the 5.3L. When I was at the dealer I checked the glove box and read the RPO codes. I dunno why I thought GU5 was a better gear than it was. That's what being in a hurry gets you.

But hey what can ya do. So the truck has 3.23s and I'm thinking about slipping a deeper gear set in the back. Perhaps a 3.73, and go ahead and throw a Detroit True Trac in there for ***** and giggles before the G80 decides to commit suicide.

The truck makes OK gas mileage but I bomb around town a bit, too. I'd say my driving is a good 50/50 highway and town mix. What would 3.73s do to the gas mileage? I know my speedo reads 3 MPH slow right now and my gas mileage is coming out at around 15.5-16 MPG. I dunno if the 3 MPH speedo change will affect that greatly. If I recall I'm turning around 1750 RPM at 70 MPH right now. I can roll at 90 MPH with the converter locked and still be hovering shortly above 2000 RPM. 90% of the time I usually cruise at 70-75.

I'm not really looking to do this to change MPG. It doesn't really bother me. Just don't want to make it worse, lol. I'd like to make the truck a little zippier (well as much as this yacht can be) and be easier on the trans when I pull things.

Thanks!

-Chris

And a pic of the truck in question: (Anyone want a tonneau? lol )

Jake99

iTrader: (5)

A most 3.73 is most likely gunna net you the best mpg, and that are a good all around gear also, my dads trucks has them on his 02 and get 20mpg on the hiway all the time, i would go with the 4.10 just because thay wont hardly hurt the mpg any and you will pick up a little more getup and go, and thay dont down shift on the big hills as ease.

SimpleGreen

Oh? Hmm.

Ya, I'm just not sure where these trucks are most efficient at yknow. But I can't believe they even sold these big ole' trucks with a 3.23 rear end. Must have been the EPA's idea.

FWIW, the only 'performance' mods I plan on are a CAI, cat back exhaust, custom tune, etc. Things like that. It's just the people hauler. I have a '93 step side to throw away money at to go sort of fast in, lol.

More opinions welcome

pasadenaman

iTrader: (3)

I just went fro 342 to 373 + truc track. Once I break it in, Ill give you an update. My co-worker has posi 373 on his 05 'burban and it hauls ***. IT accelerates fast from 0mph. He drives it like a Sports car some times but I like how his accelerates.


Check out this thread on gear selection and install

GMCtrk

iTrader: (27)

4.10s dont hurt mileage? ha ha ha. I beg to differ...

SimpleGreen

Ya I checked that thread out. Good info. I'll probably end up having a shop do the swap however. The amount of money I'd spend on getting the tools that are idea to have (but I don't) and the time spent I'd just as soon pay someone who knows what they're doing yknow.

Mostly I'm just interested to see if there are any adverse affects in gas mileage, etc. If its not going to be any worse than it is now than I feel its worth it and would be an ideal upgrade to pep up the truck

PathfinderJr

iTrader: (6)

I have 3.73's in my truck but with the 4.8. I can pull down dang near 23mpg gong 65mph on the highway. With a bigger truck and slightly larger engine, I'd bet you'd still be able to get 20 or 21 on the highway.

I was talking to my dad today and I'm pretty sure he was saying on their recent trip to the Big Bend area he was getting 22mph going 70-75mpg down the road. He has a totally stock 5.3 ECSB with 3.42.

Hope this helps. I'd say for a street truck do 3.73 or 4.10 and call it good.

james8997

im comin over tonight and pulling tha side molding off

SimpleGreen

Rofl. I pulled the Silverado badge off the tail gate a week ago. The paint is lighter under the badges than the rest of the truck. Funny what 5 years of sun light will do. I dunno how I'm gonna be able to debadge this truck now.

fastnblu

iTrader: (2)

3.23s are indeed for help meeting CAFE. As for 4.10s not hurtin mileage, I don't believe that for a second. If a truck previously had 3.73s, a swap to 4.10s might not hurt MPG. But a jump from 3.23 to 4.10? Really? I'm sure it'll **** & get like never before, but cmon. Why doesn't GM put 4.10s in all their trucks then? Answer in red.

Results are gonna vary in terms of MPG, whether some gain or lose. That & efficiency are tied in many factors. It's no 1 size fits all blanket statement. In no order, driving habits, tune, cam, convertor & gear all tie into the where's it most efficient/ MPG as far as I'm concerned.

I'm gonna have to check that thread out.