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Discussion Starter · #1 ·
Debating 4.10 or 4.56 for my 12 Sierra 5.3L, 6L90E, diablo 87 tune (mostly cause super is $$$) and 285's. Stock is 3.42, 3.73 would bring it back to stock, and 4.10 would be a jump above. I dont tow much and dont plan on it anytime soon, I commute quite a bit on the hwy 70-80mph for a good 80 miles round trip 5 days a week.

My mpg is pitiful, currently getting bout 14.5-15mpg highway, although AFM is off. Seems the engine lugs to much imho, I need to get it to downshift maybe 1-2 gears to pass someone.

Im thinking 4.10 would be best overall and might give me better mpg as the engine wont lug to much? 4.56 might be bit much IDK.

Found this site that sorta explains what rpm Id be at with each setup and tire size: http://www.chevysilverado1500.com/4-56- ... o-1500.php
 

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4.56 would be overkill imo especially with the 6 speed trans.

It would be a toss up for me between 3.73 and 4.10. Since you said you do a lot of highway maybe 3.73 would be best for you. But then again there isn't a huge difference between 3.73 and 4.10 so for my use which is mainly around town, I'd go 4.10 for the little extra get up.

I have 4.10 stock in my truck and I love them.

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Discussion Starter · #5 ·
Alderson said:
I swapped to 4.56 just before I put my lift kit on, and I don't recommend it if you're going to be doing highway driving.
The gas mileage is terrible.
Dont you also have 35"s or was the mpg terrible with say 31-33" size tires?

Does anyone have any real world mpg numbers for 3.73 vs 4.10? Just curious, currently I dont think it could really get much worse but IDK.
 

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CJM8515 said:
Alderson said:
I swapped to 4.56 just before I put my lift kit on, and I don't recommend it if you're going to be doing highway driving.
The gas mileage is terrible.
Dont you also have 35"s or was the mpg terrible with say 31-33" size tires?

Does anyone have any real world mpg numbers for 3.73 vs 4.10? Just curious, currently I dont think it could really get much worse but IDK.
I had 265/70 stock tires on with the 4.56 gears for about 2 weeks before the lift kit. The gas mileage wasn't as bad as it is now, but it still dropped a decent amount from stock.
 

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Well the closest real world I got is my truck and my friends truck. Both have stock size tires (265/75r16). Mine is a 2001 ecsb 5.3 with 4.10 and his is a 2000 eclb 5.3 with 3.73.

Around town we get the same 13-14mpg. Highway I get 16-17 in the summer @70mph and he gets mid to high 17 in the summer @70mph. So really not much difference at all if you ask me. At 70mph I'm running 2100 rpm and he's running little lower.

But the biggest difference is the felt power. Mine just pulls harder all around. Leave the line harder, and tows better.

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Discussion Starter · #9 ·
hmm. Im thinking 3.73 should be a nice medium in reality. I dont ever plan on towing much, very rarely a car trailer at most. Im just disappointed in the getup and go.

What I can say is I was very disappointed in the performance I got out of the truck in the mountains of NH/Vermont this past june. All I had was my 33's and tune, I was towing a converted small boat/jetski trailer with 2 sport quads and mine in the bed. Estimated total weight maybe 2000lbs. The truck literally just couldnt get out of its own way unless I locked out 5th and had tow/haul mode on. Once I got back to more flatter areas it was way better. Even worse was going through PA about 2 years back with my stock P265 goodyears, the current E load hankook ATMs I know weigh more. But the truck wasnt happy even then in the somewhat mountains of PA by the delaware water gap. I know I checked my sticker and yea it has 3.42 gears for sure.

Currently I commute 80 miles a day and 95% of it is highway driving at about 80mph. I do wonder if I was to go say 70-75mph how much it would help mpg. Ive considered buying a beater commuter because I get (per dic) 15mpg on the highway somehow. Course AFM is off and I drive pretty aggressively.

IDK.. if I make a mistake its a 2000 dollar mistake. Im thinking I should invest in a good exhaust like a borla touring or maybe magnaflow (not to loud is my goal and no drone) as I already have the airaid jr and it helped and a tune from Lew. Maybe the exhaust and better tune will help? I can always do the gears later I guess.

What i can say is I logged many, many miles for work in several 2500HD trucks. The 2006 truck I drove had 4.10 and with 245s would SCREAM on the highway-but had power 4L80 was ok. The 11 and 13 I drove were both 3.73 and one had 245, then 265 on 17's and the other one had 275's on 18s. Both felt very powerful and werent exactly screaming the highway. Considering they carried in excess of 2500lbs and the 6.0 only has approx 40-50hp more..it felt better. Even with the larger tires they felt fine.

sigh..
 

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Discussion Starter · #11 ·
ericlw said:
you drive 80 miles a day at 80 mph in a truck and worry about gas milage?
New job, it wasnt the game plan trust me. But you take what you can get. previously only was driving half of that a day and all local roads.

Also, this is NJ and if you dont do 75mph or better on the major highways you will get run off the road pretty quick. Hell I let people pass all the time when Im doing 80-85mph and they fly by me doing 90-100mph easy.
 

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Im quite sure you have a 6L80E not a 6L90E unless you did some kind of swap.
I vote for 4.10's.
You might end up saving money by purchasing a small commuter car. Something used for under $5000 with lower miles. At the least you would keep the miles off your truck. I don't usually recommend multiple vehicles but if your commuting 80 miles a day, that's where you would start to benefit from a second car.
 

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CJM8515 said:
Debating 4.10 or 4.56 for my 12 Sierra 5.3L, 6L90E, diablo 87 tune (mostly cause super is $$$) and 285's. Stock is 3.42, 3.73 would bring it back to stock, and 4.10 would be a jump above. I dont tow much and dont plan on it anytime soon, I commute quite a bit on the hwy 70-80mph for a good 80 miles round trip 5 days a week.

My mpg is pitiful, currently getting bout 14.5-15mpg highway, although AFM is off. Seems the engine lugs to much imho, I need to get it to downshift maybe 1-2 gears to pass someone.

Im thinking 4.10 would be best overall and might give me better mpg as the engine wont lug to much? 4.56 might be bit much IDK.

Found this site that sorta explains what rpm Id be at with each setup and tire size: http://www.chevysilverado1500.com/4-56- ... o-1500.php
...you're thinking is backwards. you dont get better gas mileage normally going from 3.42 to 4.10 or 4.56.

I wouldnt do 4.56 unless you're on 37s or bigger or if you tow heavy weight. (6k+)

If you really needed 4.56... then i think you need a 2500 first.

I had a 2011 1500 5.3 with 3.08 gears (6spd).... UGH. moved to a 2004 2500HD with 4.10 (4spd OD).... and good gawwwh its so much nicer.
i dont even have a need to go to 4.56.
 

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doing 80 mph in a brick is whats killing your mpg. gears aren't really going to help that, nor will the small bump in MPG offset the major cost of a gear swap.

when I set my cruise between 65-70 I will average 19mpg on 33s and 3.08s in my 15. when I bump up to 80 my average drops to 15mpg.
 

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4.10 mainly because of commute and not towing. if 3.73 brings it back to stock then 4.10 will compensate for the extra rolling mass.
 

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Discussion Starter · #16 ·
ferraiolo1 said:
doing 80 mph in a brick is whats killing your mpg. gears aren't really going to help that, nor will the small bump in MPG offset the major cost of a gear swap.

when I set my cruise between 65-70 I will average 19mpg on 33s and 3.08s in my 15. when I bump up to 80 my average drops to 15mpg.
Of course I realize this. But it doesnt help either having to hit the throttle pretty hard to bring it outta OD to pass all the time. I think Ill resolve to go closer to 70-75mph if possible, but the fact remains if you arent doing around 75mph to start you may get run down on the highways I travel.

I think what Ill do is live with it for now, slow down a bit to preserve mpg and then work on adding an exhaust and Lew's tune first. If Im unhappy with that Ill do the gears. But in the meantime its time to go look for a car of some kind.

before I took this longer commute job I had been contemplating buying an 11+ 2500HD 6.0 and buying a car anyways.
 
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