VEGASROBBI

Go with the LS3 430 HP engine, idles at 600 rpm and has good bottom end torque. The LS3 480 HP engine can use an automatic transmission, but is marginal for crawling; however, it is great on trails or the street. The 525 HP engine needs a manual transmission.

To be fair when comparing these engine you must look at the set up, they all put out good HP. GM has a tendency to run 3:21 gears in a lot of their Truck/SUV's which in a 6,000 lb. truck kills the performance. I had a customer with a 5.3 Suburban who almost sold it because the tall gears and lack of performance, he regeared it and now loves it. A 6.2 LS with good gearing and a 4:1 low 6l80 launches like a go kart in a heavy JK. I can't count how many test drives I have been on where a guy gets out of a V6 JK, Hemi or SC JK and gets in a LS JK with the 6l80, first time they hit the gas they usually chirp the tires, they weren't expecting the instant response.

I think Ford is better at getting performance through gearing than GM is since GM is obsessed more with mpg numbers.

greenenvey

Actually our 2011 was no slouch but the 2014 runs very strong. As far as you being worried that the ls3 corvette engine don't have enough on the bottom end believe me it does. My jk with 37, s and 538 gears would really saprise you. When you get on the gas hard the back end squats and the front rises and you're off to the races lol. Seriously though it's a fantastic engine for the jk.

rws

I don't crawl in this Jeep at all, and when it does go off road it's on back country dirt roads going to different farms as my daughter rides horses.. So high speed dirt roads is what my Jeep is set up for.. How does the 480hp LS3 sound with 6:17 gears on 40's for the type of setup?

Tooadvanced

6.17 gears? You sure your not crawling lol. Why not Rockwells with 6.72s? 5.13s on d60 or 80s will suffice

VEGASROBBI

I'd recommend 5:13s or 5:38's with a 480 HP LS3 and 40's. The 480 is great on trails and can deliver decent mpg if you cruise around 2,300 rpm where the cam is working.

I'm not sure 6:17 gears would hold with so few pinion teeth.

rws

Believe it or not, with the way the 9" gears are cut, the higher the ratio the stronger the gear set is.. Unlike the Dana's which will use less teeth on the pinion to raise the gear ratio, the 9" starts to cut the teeth diagonal which gives the higher gear ratio more tooth contact.. I don't understand the engineering of it at all, but there's a great write up on how it's done.. I can find and post it if you're interested, I thought it was really cool and explains why the 9" has been king for so long.. They say the high 5's and low 6's are the strongest gear set for them which is what the trophy trucks, hammer buggies, nascar, etc. all use.. Just a regular Moser 3rd member with those gears are rated for 3000+hp.. I haven't done the math, and haven't been able to find the formula for rpm and tire to give you a correct gear ratio, but I figured a low gear like that would really help the two overdriven in the 6l80 pull better like dropping the gears from 3:55 to 4:10 in the z06 did wonders, but you'd know better with the jeeps than I.

rws

I know it sounds crazy low, but there's a chart here somewhere that shows tire size, gear ratio, and rpm turning for the jk, and with the 6:00 you're turning up 2400rpm at 70mph, which I was very surprised at.

rws

Here it is.. I figured this could be a decent guide if the 6l80 transmission and the jk transmission have a similar overdrive ratio. That make sense?

VEGASROBBI

I have Moby at the shop running 40's with a D80 and 60. Moby is turning about 2,300 @ 70 mph. There is a trade off between performance and economy. Moby's getting 12-13 mpg on the highway; I think with 5:13's it could be closer 15. Since Moby wheels a lot 5:38's work well.

One reason the 6l80 works with taller gears and two overdrives is the 4:1 first gear. Even 37's with 4:10's feel peppy off the line.

I think it's a mistake to gear a 6.2 6l80 like you would a SC V6 or Hemi, unless you crawl a lot your needlessly spinning the engine up and shifting more than you need.

rws

This is extremely helpful and what I've been trying to figure out for months on end. I suppose a should've just asked instead of driving myself crazy searching for formulas and charts