I'm getting ready to swap my stock 3.42s for 4.11s. Has anyone done this yet? I have a 2006 crew cab Z71 with 20x12s and 32x1250 tires. What are the differences in rpms and gas mileage yall have noticed. I've done a few gear ratio calculaors and they say around 70 mph i'll go from about 1,700 (3.42s) to 2,100 (4.11s). I know my city mpg will probably increase. Really wondering the difference in hwy will be. Any input would be awesome. All in all i know i'm going to enjoy the 4.11s for fun

 

Are you doing the front and rear gear sets? I believe you have to.

With a 31 inch tire @ 75, I turn about 2500 rpms.

At that speed while cruising, the DIC displays 20-21mpgs but it usually averages out to around 18mpg on a trip.

 

Yeah I already have front and rear master install kits, just waiting for my appointment to get here! And wow that's great man, I avg about 18.5 hwy mpg as long as I keep it around 65-70mph, that's with a custom tune and 3.42s.. I also have a full custom exhaust, Volant CAI and TBS, LTs, highflows and super 44s with an x pipe, 2.5" pipe to 4" tips... I figured I would drop some mpg on hwy, not that it matters a whole lot, I just didn't want to be getting like 12-14 lol

 

I'm in! Looking to do these gears on my 3/4 ton on "35's", 8 miles per gallon in town is killing me! And the lack of spinning tires.. That's with 3.73 gears!

 

yes do it! that way i know what to expect when i do my LQ9 swap

 

Hey now! I was gonna wait to see how yours turned out first, then I'll deside on gears! You going with a 4L80 with the swap?

 

Yeah i most likely do the 4l80.. I've been researching on gears for weeks now, and from what i've been told, you will not be disappointed lol its kind of a heavy price take, especially being a 4x4, $1,200 from parts and labor for front and rear. but it'll be so worth it.. especially someone with a heavy truck like yours.. they say with 35" tires you should be running a MINIMUM of 4.11s to get you back to factory ratio basically.

 

With my 07 I went from 3.42s to 4.10s and it ran .64 better in the 1/8th with 32's. Mileage was great. 3.42's to 3.90s with 31's in my 99...still great mileage.

 

I did the swap 342s to 411s on z71 running 33s average mpg is 14.5 stop n go.
Made a trip on the interstate at 70mph for an hour it got 16.
Drives much better tho!

 

wow thanks guys! appreciate the input! cant wait to get this things in!