rkmurphy526 Posted April 17, 2017 Share Posted April 17, 2017 Currently have a 2014 Silverado Z71 2WD with 3.42 gears. I've done the RC 2.5" level and popped some 33's on it (really 32.6") and noticed a drop in mpg and towing mpg. The truck sees about 25K miles per year as it's my daily driver (mostly highway) and I'm towing a 5,000 boat package (including trailer and all) about 1-3 times/month. My question is, would upgrading to the Zone 6.5" system and 35's (really 34.8") necessitate upgrading my rear differential to say 4.10? Or am I safe to stick with my existing gears? Any experience with this setup? I'd like to avoid the cost of a gear swap but obviously want to stay practical and reliable. I'd like to get 200K miles out of the truck if I can help it. Thanks! Link to comment Share on other sites More sharing options...
jimmyboy8301 Posted April 17, 2017 Share Posted April 17, 2017 If you have a 5.3/6spd although not optimal the 3.42s will be ok Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Dana Mills Posted April 17, 2017 Share Posted April 17, 2017 I would swap, personally. I have 3.73 with 33s and feel like I'm at the limit to prevent crappy shifting/loss of power/loss gas mileage etc. See this chart just as as guide Link to comment Share on other sites More sharing options...
rkmurphy526 Posted April 17, 2017 Author Share Posted April 17, 2017 Thanks for the replies everyone! Keep the info coming. My only concern with that chart is that it's basically saying I need 4.10s with stock tires...not sure that makes much sense. But I could be looking at it wrong. Link to comment Share on other sites More sharing options...
Juanitos2008 Posted April 20, 2017 Share Posted April 20, 2017 Thanks for the replies everyone! Keep the info coming. My only concern with that chart is that it's basically saying I need 4.10s with stock tires...not sure that makes much sense. But I could be looking at it wrong.that chart is for 4l60e transmissions Sent from my SM-G935T using Tapatalk Link to comment Share on other sites More sharing options...
Thornton Posted April 29, 2017 Share Posted April 29, 2017 There are plenty of folks in the Lift thread that say they have 3:42 and can chirp their tires still with 35's and its wasnt a problem Link to comment Share on other sites More sharing options...
arkenzo Posted April 29, 2017 Share Posted April 29, 2017 I would swap, personally. I have 3.73 with 33s and feel like I'm at the limit to prevent crappy shifting/loss of power/loss gas mileage etc. See this chart just as as guide I think the 3.73's are perfect for 35s, 3.42's will be just fine, some even have 35's on 3.08's and are satisfied. Link to comment Share on other sites More sharing options...
hou1ptt Posted April 29, 2017 Share Posted April 29, 2017 IMO - Ideal setup.. Plenty of power & mine would spin the tires with 35" MT.. I do have tuned, headers, exhaust, etc.. NO NEED TO CHANGE even with 37.5".. Up to you. IMO - Ideal setup.. Plenty of power & mine would spin the tires with 35" MT.. I do have tuned, headers, exhaust, etc.. NO NEED TO CHANGE even with 37.5".. Up to you. Link to comment Share on other sites More sharing options...
Dezrado Posted April 29, 2017 Share Posted April 29, 2017 I have 3.42 with 35s with black bear tune and they move!! I do have an avg mpg of 14 mix of city and highway. 15-16mpg on highway not towing on 91 octane. If mpg was a big concern for me i would go 4.10 but i have 4wd so thats double the cost to regear Link to comment Share on other sites More sharing options...
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