I joined the 3.42 club

[pacem]

GU6 it is. I was hoping for 3.73, that would be a sweet combination but you cannot have everything.

Get about 16.6MPG in mixed driving - mostly city and expect to hit 20MPG highway only. A refreshing change from 11MPG I got with 6.0L. It moves a little slower 0-60 than the 6.0L with 3.73s but the mileage difference is huge.

Thus far I've had two 3.73s, 4.10 in a Ford, 3.23 in a Caprice wagon - I think 3.42 strikes a sweet spot in terms of MPG/power balance. I don't think it's ideal for towing but I hardly ever tow. It is impressive how low RPMs stay.

 

[swathdiver]

Imagine how much the motor would loaf around with 3.08s! I like the 3.42 gear and overdrive. Reminds me of my Buick Grand National days, same rear, gear and I think the OD ratio too. Turns about 2000 at 80 in 6th.

 

[conchasjim]

I've got a 07 with the 5.3 and 3:42 rear end. 2 wheel drive. It tows terrible. No power up the steep grades. Constantly down shifting. I even tried a superchips tuner with the tow mode tune. No help. I'd like to try a 3:73 gear ratio. Any one have some input? Fuel mileage is not a great concern as it's no gas miser right now.

 

[pacem]

You definitely need 3.73 for towing, I sometimes wish I had that even though I don't tow.

 

[swathdiver]

I've got a 07 with the 5.3 and 3:42 rear end. 2 wheel drive. It tows terrible.

4-Speed Trans right? 3.73s was the factory gear for towing with that 4L80. Some also use 4.11s.

 

[conchasjim]

Yes, it's a 4 speed LTZ with 3:43.

 

[swathdiver]

Yes, it's a 4 speed LTZ with 3:43.

Well, I'm not telling you anything new then that the 4-speeds tow best in front of a 3.73 or 4.10 gear. The 6-speed trucks can get away with the 3.42s while towing.

 

[Kenny D]

I got the 3.08 and a 6 speed. At 80mph I am about 1600 -1700 rpms. Haven't done a road trip to check hwy mileage but I get 16.9mpg on my weekly commute. Some high speed freeway with occasional stop and go traffic. AFM is disabled.

 

[HotCarl]

Got a '13 burb with the tow package and 3.42s. Averaged 19.9 mpg on a 300 mile trip today, majority of it on 65mph state highways with a few 7% grades too. You are right on target at 20 mpg straight highway.

 

[swathdiver]

Got a '13 burb with the tow package and 3.42s. Averaged 19.9 mpg...]

What kind of tires are those in your signature photo? Same as the mileage check?