Need advice 3.42 or 3.73 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BP68 · 01-31-2008, 04:43 AM

Hello all,

I asked some questions about a year ago on rearend gears, and never really made any decisions.

I have a 06 Silverado 1/2 2wd Ext. Cab 5.3 with 3.23 gears and 275/55R20,Flowmaster and drop in K&N. Runs pretty good, but could use a little better punch off the line and in passing gear.

It is a daily driver mostly city driving. Ocassional highway driving and very ocassional towing/hauling. I average right around 14mpg give or take a few tenths.

What would my best bet be 3.42 or 3.73? I am looking for more performance/seat of the pants feel, but don't want to totally sacrifice mpgs.

One person told me that with the 20's and 3.23 the motor is prob not getting up into the optimal rpm range, and that 3.42 could possible help mpgs by letting the motor rev up a little more.

Basically, what gears are y'all running and what mpgs are you getting.
Would I see a big diff in mpgs (good or bad) between 3.42 and 3.73? Should I just go 3.73?

Thanks

Pl4yboy · 01-31-2008, 09:24 AM

I have a 07 with a 4.8 and 3.73s. I average right around 18 MPG when I keep my foot out of it. I do still have the stock wheels and tires though.

502tripower · 01-31-2008, 10:43 AM

Quote:

Originally Posted by BP68

Hello all,

I asked some questions about a year ago on rearend gears, and never really made any decisions.

I have a 06 Silverado 1/2 2wd Ext. Cab 5.3 with 3.23 gears and 275/55R20,Flowmaster and drop in K&N. Runs pretty good, but could use a little better punch off the line and in passing gear.

It is a daily driver mostly city driving. Ocassional highway driving and very ocassional towing/hauling. I average right around 14mpg give or take a few tenths.

What would my best bet be 3.42 or 3.73? I am looking for more performance/seat of the pants feel, but don't want to totally sacrifice mpgs.

One person told me that with the 20's and 3.23 the motor is prob not getting up into the optimal rpm range, and that 3.42 could possible help mpgs by letting the motor rev up a little more.

Basically, what gears are y'all running and what mpgs are you getting.
Would I see a big diff in mpgs (good or bad) between 3.42 and 3.73? Should I just go 3.73?

Thanks

The 3:73's will work perfect for what you are trying to accomplish. I can't believe that truck has 3:43's. Almost all of the 1500's 5.3 use the 3:73's.

mixermike · 01-31-2008, 11:12 AM

i have a 2000 gmc,5.3 with 3.73 and i love them

Pyrotechnic · 01-31-2008, 11:47 AM

3.73's are the sweet spot for these trucks with a 5.3 or 6.0. I don't know why the even bother offering 3.23's since these trucks have overdrive.

BP68 · 01-31-2008, 12:20 PM

Keep them comments comming, but sounds like 3.73's it is.

502tripower · 01-31-2008, 12:24 PM

I have both the 5.3 and the 8.1 with the 3:73's. Only way to go. The 8.1 is also offered with the 4:10's but I like the 3:73's

Joe67 · 02-07-2008, 10:52 PM

3.73 is a great all around gear

Huck · 02-23-2008, 08:58 AM

Most stock 5.3s come with 3.42 which is a great gear setup--ie performance balance to MPG. IF you have the tow package, you get 3.73 which also give you that grunt pull you need towing a load. My 02 has 5.3 with 373 and will get 19mpg over the road running 17's. If off the line is important to you, go 3.73's. With 20" wheels, you will not get a strong quick launch without a deep rear gear. Just the nature of the physics.

skokie · 03-04-2008, 11:01 AM

When I bought my 01 Sierra I requested 3.42 since I knew that I would not be towing anything with it and driving across country. Gas mileage is great and 75 is exactly 2000 rpm

80 is about 2150 - 2200. If I had planned to tow anything it would have been 3.73 all the way.

odie82 · 03-06-2008, 06:50 PM

[QUOTE=Huck;2591525]Most stock 5.3s come with 3.42 which is a great gear setup--ie performance balance to MPG. IF you have the tow package, you get 3.73 which also give you that grunt pull you need towing a load.QUOTE]

no, my 06 gmc 5.3l has the tow package and still has the 3.42 gear ratio, it really sucks, I want the 3.73 bad

Eichorst69 · 03-06-2008, 08:48 PM

My 2004, Z-71, 5.3 4x4 has 3.73's and gets 14.1 MPG.

Rob

67ChevyRedneck · 03-07-2008, 02:29 AM

I have an ext cab Z71 4x4 w/ 5.3L and 3.73 rear. I'm getting 14-15 around town and 18+ on the highway.

finch · 04-05-2008, 09:16 PM

my 2005 1500LD crew with the 5.3 and 3.73's gets right around 15 avg, but i have seen as high as 16.9 and as low as 11.8 with mixed driving.

BP68 · 09-03-2009, 04:34 PM

Bringing my old thread back since I finally got the 3.73's install aftere all this time. So far loving the added bottom end grunt. I write figure my mpgs every time I fill up.
Last fill up on 3.23's = 15.39 mpg
First fill up on 3.73's = 14.93 mpg

And that is not driving it easy. Too tempted to enjoy the added grunt. All in all very happy.

Otsa580 · 09-03-2009, 09:15 PM

3.73's rock!

I loved romping my 04 crew around town.

deyomatic · 09-04-2009, 07:45 AM

According to the math, your tires aren't that much bigger than the stockers on my '05. With the 5.3 I think the 3.73s will be better, I'd go lower if I were going through the hassle of changing them, though. It's still a pretty tall tire.

**Boog** · 09-04-2009, 12:33 PM

BP I'm curious to see if you had to have your computer adjusted to compensate for the larger diameter tires and correct your speedo.? My truck has larger tires than factory and the speedo is off just a bit judging by the mile marker posts on the highway so it registers slow. If the speedo runs slow the mpg will be low too.

Gray Ghost · 09-05-2009, 10:16 AM

Quote:

Originally Posted by Eichorst69

My 2004, Z-71, 5.3 4x4 has 3.73's and gets 14.1 MPG.

Rob

My 2005 Z71 [reg cab short bed] has a 5.3/3.42 combo....I average 17.7 mpg and it runs like a scalded ape. With 3.73's I'd really be screamin', but I like the 3.42's fine. If I had a heavier truck, I'd defintely want 3.73.

fiddy9apache · 09-05-2009, 06:35 PM

my 2001 tahoe has factory 4.10s and i love them, it pulls good, full to drive.

*nekkidhillbilly* · 09-08-2009, 11:31 PM

my 4.8 4x4 with 373 got no less than 18 mpg ever

BP68 · 09-18-2009, 10:49 PM

Quote:

Originally Posted by Boog

BP I'm curious to see if you had to have your computer adjusted to compensate for the larger diameter tires and correct your speedo.? My truck has larger tires than factory and the speedo is off just a bit judging by the mile marker posts on the highway so it registers slow. If the speedo runs slow the mpg will be low too.

First off 3rd fill up with new gears 15.360 mpg. Keep in mind this is primarily city driving back and forth to work, with me driving a little hard and running the air most of the time.

To answer your question Boog - I work for a Chevy dealer as a service tech. I installed the wheels/tires right after buying the truck in 2006 and I reprogrammed it myself with calibrations I got from GM. I did the same thing after the gear install.

**Boog** · 09-19-2009, 09:06 AM

It's great you now have more grunt and getting near the same mpg as with the original gears. It was a good move. Thanks for the update.

01-31-2008, 04:43 AM	#1
BP68 Registered User Join Date: Jun 2006 Location: Olive Branch, MS Posts: 824	Need advice 3.42 or 3.73 Hello all, I asked some questions about a year ago on rearend gears, and never really made any decisions. I have a 06 Silverado 1/2 2wd Ext. Cab 5.3 with 3.23 gears and 275/55R20,Flowmaster and drop in K&N. Runs pretty good, but could use a little better punch off the line and in passing gear. It is a daily driver mostly city driving. Ocassional highway driving and very ocassional towing/hauling. I average right around 14mpg give or take a few tenths. What would my best bet be 3.42 or 3.73? I am looking for more performance/seat of the pants feel, but don't want to totally sacrifice mpgs. One person told me that with the 20's and 3.23 the motor is prob not getting up into the optimal rpm range, and that 3.42 could possible help mpgs by letting the motor rev up a little more. Basically, what gears are y'all running and what mpgs are you getting. Would I see a big diff in mpgs (good or bad) between 3.42 and 3.73? Should I just go 3.73? Thanks __________________ 68 C10 Shortbed Fleetside 06 Chevy Ext Cab Fleetside 03 Grand Prix GTP My build thread http://67-72chevytrucks.com/vboard/s...d.php?t=269999

01-31-2008, 09:24 AM	#2
Pl4yboy Freeeeee Mason... Join Date: Sep 2006 Location: McAlester, Oklahoma Posts: 320	Re: Need advice 3.42 or 3.73 I have a 07 with a 4.8 and 3.73s. I average right around 18 MPG when I keep my foot out of it. I do still have the stock wheels and tires though. __________________ Daily Driver -2007 Chevy -Dark Blue Metallic -Regular Cab -4.8 V8 -4x4 Ongoing, Never Ending, PITA, Love of my Life -69 Chevy C/10, Camper Special -350/TH400 -Loudest System on the Board

01-31-2008, 11:12 AM	#4
mixermike Registered User Join Date: Jan 2008 Location: Post Falls, Idaho Posts: 606	Re: Need advice 3.42 or 3.73 i have a 2000 gmc,5.3 with 3.73 and i love them

01-31-2008, 11:47 AM	#5
Pyrotechnic Registered User Join Date: Feb 2007 Location: Austin, TX Posts: 3,930	Re: Need advice 3.42 or 3.73 3.73's are the sweet spot for these trucks with a 5.3 or 6.0. I don't know why the even bother offering 3.23's since these trucks have overdrive.

01-31-2008, 12:20 PM	#6
BP68 Registered User Join Date: Jun 2006 Location: Olive Branch, MS Posts: 824	Re: Need advice 3.42 or 3.73 Keep them comments comming, but sounds like 3.73's it is. __________________ 68 C10 Shortbed Fleetside 06 Chevy Ext Cab Fleetside 03 Grand Prix GTP My build thread http://67-72chevytrucks.com/vboard/s...d.php?t=269999

01-31-2008, 12:24 PM	#7
502tripower Registered User Join Date: Jan 2008 Location: Satsop, WA Posts: 606	Re: Need advice 3.42 or 3.73 I have both the 5.3 and the 8.1 with the 3:73's. Only way to go. The 8.1 is also offered with the 4:10's but I like the 3:73's __________________ 1963' Chev Custom Cab 502, 67' 435hp 3X2 intake, 9" 4:30 Posi 1961 Impala SS 348/350 4-speed 3:70 Posi 1961 Bel-Air Bubble Top 283 Turboglide soon to have a 348 3X2 4-speed 1950 17' Fairliner twin cockpit barrel stern 312 Y block 1X1 intake Borg Warner 1:1 gear 1957 Fleetform 14' twin cockpit barrel stern 1969 BP-125 Merc 1949 Transitier 3-wheel forklift Crosley 4-Banger 98' FXD 2002 2500HD

02-07-2008, 10:52 PM	#8
Joe67 67 is sold Join Date: Apr 2001 Location: Troy, Michigan Posts: 6,733	Re: Need advice 3.42 or 3.73 3.73 is a great all around gear __________________ Joe - Formerly 67c10step ------------------------------- 1967 Chevy Stepside - ECE 4/6, fuelcell, 5lug - SOLD gr8lakes - My ebay auctions Click here to order forum apparel :: Click here to become a subscribing member Last edited by Joe67; 02-07-2008 at 10:52 PM.

02-23-2008, 08:58 AM	#9
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,261	Re: Need advice 3.42 or 3.73 Most stock 5.3s come with 3.42 which is a great gear setup--ie performance balance to MPG. IF you have the tow package, you get 3.73 which also give you that grunt pull you need towing a load. My 02 has 5.3 with 373 and will get 19mpg over the road running 17's. If off the line is important to you, go 3.73's. With 20" wheels, you will not get a strong quick launch without a deep rear gear. Just the nature of the physics.

03-04-2008, 11:01 AM	#10
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,354	Re: Need advice 3.42 or 3.73 When I bought my 01 Sierra I requested 3.42 since I knew that I would not be towing anything with it and driving across country. Gas mileage is great and 75 is exactly 2000 rpm 80 is about 2150 - 2200. If I had planned to tow anything it would have been 3.73 all the way. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

03-06-2008, 06:50 PM	#11
odie82 Registered User Join Date: Jan 2004 Location: minnesota Posts: 349	Re: Need advice 3.42 or 3.73 [QUOTE=Huck;2591525]Most stock 5.3s come with 3.42 which is a great gear setup--ie performance balance to MPG. IF you have the tow package, you get 3.73 which also give you that grunt pull you need towing a load.QUOTE] no, my 06 gmc 5.3l has the tow package and still has the 3.42 gear ratio, it really sucks, I want the 3.73 bad __________________ 1982 chevy C-10, blue 2wd shortbox 17x9 cragar ss rims, 350V8-th400 2003 suzuki gsxr 1000-hit 175mph!!! yeah it's fast-no you can't ride it

03-06-2008, 08:48 PM	#12
Eichorst69 Registered User Join Date: Jan 2007 Location: South Florida Posts: 158	Re: Need advice 3.42 or 3.73 My 2004, Z-71, 5.3 4x4 has 3.73's and gets 14.1 MPG. Rob

03-07-2008, 02:29 AM	#13
67ChevyRedneck Hittin E-Z Street on Mud Tires Join Date: Nov 2004 Location: Greenville, SC Posts: 23,090	Re: Need advice 3.42 or 3.73 I have an ext cab Z71 4x4 w/ 5.3L and 3.73 rear. I'm getting 14-15 around town and 18+ on the highway. __________________ Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride American Born, Country by the Grace of God 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications!

04-05-2008, 09:16 PM	#14
finch Registered User Join Date: Dec 2007 Location: Sioux Falls, SD Posts: 365	Re: Need advice 3.42 or 3.73 my 2005 1500LD crew with the 5.3 and 3.73's gets right around 15 avg, but i have seen as high as 16.9 and as low as 11.8 with mixed driving.

09-03-2009, 04:34 PM	#15
BP68 Registered User Join Date: Jun 2006 Location: Olive Branch, MS Posts: 824	Re: Need advice 3.42 or 3.73 Bringing my old thread back since I finally got the 3.73's install aftere all this time. So far loving the added bottom end grunt. I write figure my mpgs every time I fill up. Last fill up on 3.23's = 15.39 mpg First fill up on 3.73's = 14.93 mpg And that is not driving it easy. Too tempted to enjoy the added grunt. All in all very happy. __________________ 68 C10 Shortbed Fleetside 06 Chevy Ext Cab Fleetside 03 Grand Prix GTP My build thread http://67-72chevytrucks.com/vboard/s...d.php?t=269999

09-03-2009, 09:15 PM	#16
Otsa580 I Love Rusty Chevys Join Date: Jan 2009 Location: Omaha, NE Posts: 617	Re: Need advice 3.42 or 3.73 3.73's rock! I loved romping my 04 crew around town. __________________ 1969 K5 Blazer 1997 1500 Silverado Ext Cab Z71 2010 1500 Silverado Ext Cab Z71



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09-04-2009, 07:45 AM	#17
deyomatic Registered User Join Date: Oct 2008 Location: Wethersfield, CT Posts: 39	Re: Need advice 3.42 or 3.73 According to the math, your tires aren't that much bigger than the stockers on my '05. With the 5.3 I think the 3.73s will be better, I'd go lower if I were going through the hassle of changing them, though. It's still a pretty tall tire. __________________ _____________________________________________ 1960 F100 (soon to be SBC/700R4) 2005 GMC Sierra

09-04-2009, 12:33 PM	#18
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,683	Re: Need advice 3.42 or 3.73 BP I'm curious to see if you had to have your computer adjusted to compensate for the larger diameter tires and correct your speedo.? My truck has larger tires than factory and the speedo is off just a bit judging by the mile marker posts on the highway so it registers slow. If the speedo runs slow the mpg will be low too. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

09-05-2009, 06:35 PM	#20
fiddy9apache Registered User Join Date: Aug 2009 Location: ftw tex Posts: 682	Re: Need advice 3.42 or 3.73 my 2001 tahoe has factory 4.10s and i love them, it pulls good, full to drive.

09-08-2009, 11:31 PM	#21
nekkidhillbilly Account Suspended Join Date: Apr 2009 Location: hazard, ky Posts: 1,674	Re: Need advice 3.42 or 3.73 my 4.8 4x4 with 373 got no less than 18 mpg ever

09-19-2009, 09:06 AM	#23
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,683	Re: Need advice 3.42 or 3.73 It's great you now have more grunt and getting near the same mpg as with the original gears. It was a good move. Thanks for the update. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

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