Looking for others who have done an LS swap to chime in please!
On my 2 dr JK: Running an early LS (5.7, aluminum block) mated to a 4L80. Geared 5.13, and somewhat heavy beadlocks/ and tires (35's). Rear armor, skid plate, etc.
I'm managing all of 11mpg combo hiway/street driving. I'm struggling with such poor mpg, but would really need to hear what others have been experiencing with similar rigs. With no basis for comparison, can't decide if I can complain or not!
Thanks

 

I'm running a 6.0L (L96) with a 6L80E. The JKU weighs in at just under 5500 lbs, I'm running 4.10 gears and BFG MT KM2s (35x12.50x17). Around town I get 12-14 and on the interstate I get 16 or so mpg.. so long as I keep my foot out of it.

 

Wow 11 mpg out of a 3.83 litre American gallon? Man it's going down the drain somewhere.
Is your foot heavy or you leave it parked idling a lot? Something ain't quite right.

 

No kidding, right?
Nope, with that mileage I've got a verrrrry light foot.

 

I'm hoping to hear from someone with similar gearing. I can't imagine the 4L80 v 6L80 would make such a big difference, but don't have a handle on the impact of the 5.13's.

 

Best I can give you to get in the ballpark on comparison is at 70mph I'm turning 1800 rpm.

 

Interesting, with the 4l80, I'm turning approx 2900 rpm at 72 mph.

 

Yup... this is helpful - 4Lo.com :: Final Gear Ratio, Crawl Ratio, Tire Size Calculators

I have a sixth gear that is 0.67, your 4th gear is 0.75

Diff in mine is 4.10, yours is 5.13

All else is close to equal.

 

I have a 4 door with 35's and 5.13 gears running a 6.0 with 6l80e and at 75 mph I am turning 2475 rpms. At 60 mph I am turning 1900. At the 2475 rpms I am getting around 11-12 mpg city/highway. I have not had a chance to run at 60 mph on a tank to get the mileage but I have heard that these motors should really be cruising at 1900-2100 rpm's. Afraid gears are to low but I dont want to spring for a gear change now. Wish I could find someone that has 4.56's that would want to trade axle assemblies with as that ratio would put me at 2200 rpm's at 75 mph, 2081 rpm's with 37's haha.

 

Thanks, so what I take from all this is that in my case, the 4L80 was not a good match. I should have looked harder for a 6L80 which would have helped out a bit on rpms. I really like the 5.13 wheeling and would not want to give it up, so I guess I'm stuck. Time to save for a DD I can afford to run!