I have a 2006 silverado 1500 with 5.3L Vortec and 3.42 gears. Towing is a real issue, especially in the summer with the AC on. Tinkering with the idea of switching the gears over to 3.73. I know that it will affect fuel mileage, but not sure how much. Anyone done this?

 

What are you towing?
New here as well, I have a 96 dodge 1500 with 4:10's I use to haul my boat. It made a huge difference in towing, an with fuel mileage etc.

 

3:42 gears are more of a highway gear for better mpg but 3:73s are more so a towin gear. if you want real power 4:10s may be in order. especially if you tow a lot. 3:42 gears compared to 3:73 gears there's not much of a gas mileage difference. honestly like less than 200 rpms at cruising speed then the 4:10s are like 200 rpms over the 3:73s. either way if you switch gears then you'll have to get a custom tune or have the stealership reprogram it because your speedo will be off andyour shiftin will be screwed up.


if you tow a lot get 4:10s if not then get 3:73s. that's what I have stock and it pulls ok but since I put 33s it's not near as good as stock an will be upgrading to 4:30s soon

 

I have 2013 Tahoe 4x4 5.3L factory Vehicle. 11 to 13.4 MPG. Hills are a night mare. Below 50 MPH the truck screams at 2500 to 3500 RPMs to maintain normal speeds. 35,000 and I need Tranny work due to constant downshifting. Hate my 342 gear.

 

The manufacturers sell a lot of low MPG trucks and still need to meet the federal fuel economy standard or CAFE for their overall vehicle sales. They will go to taller gears to squeeze out an extra 1 MPG at highway on the EPA tests, which are bogus anyway as they use a highway speed of 55 MPH where air drag is 50% less than at 65 MPH.

For towing with a gas engine I want 4.10 gears to keep the engine in its peak power band. I have put more than 175K miles on 5 trucks and a full size SUV and my average MPG was 16-17 MPG for them all. I see the new 8-speed transmission equipped SUV's and full size pickups with a rated MPG of 18 by the EPA and have to wonder why the engineers have not managed to improve fuel economy for these vehicles over the past 20 years.

 

they have improved mpg. the new fuel mileage rating system has changed; making the new vehicle appear to have poorer mileage when comparing new to old epa ratings.


the new di gas engines are much more efficient. in some driving modes up to 30% as they can really lean out the f/a ratio. small displacement di turbo charged engines will soon become the new standard in gasser fuel economy.

 

I like my 2500 Burb with the 3.73 and the six speed.

However, the Denali with the 3.42, 6-speed and the 6.2 is certainly not lacking for power. It's nice that the engine loafs just below 2k when cruising at 70 MPH. Haven't towed with it yet, but I figure the extra 50 HP should make up for the "less than optimal" rear end ratio.

If you are stuck with the 4-speed transmission, the 3.42 trucks are dogs.

 

I know, old thread.y 2008 Sierra z71 with 5.3 w/ 3.42/ 4l60 will break the tires loose for maybe 500-600 or so feet on dry pavement. It is a runner. May have had a mild cam or a major tune before I owned it or I just got a good one. It could do a little better towing but it's not bad and I only tow (6500ish lbs) occasionally. I test drove an Avalanche with the same set up before I bought the Sierra and it was a dog.