Like I said, I don't even have my Rubi yet, so I'm just looking strictly at the numbers of it all.

FWIW, what RPM are you runnin' at 90mph?

I agree that 5.13's with a 6spd 1st gear of 4.46 and a 4:1 low range would be wicked. My plan includes an Atlas 4spd with the 10.34:1 low range. How you think that'd be?

 

I've never understood if regearing will help or hurt your gas mileage. I know theoretically it should get less MPG but most report a gain.

 

I am out of the country or I could go check it for you....think it was in upper 4's but it was not too close to red-line, I even had a little skinny pedal left.

With that Atlas you will CRAWL over ANYTHING!!!!!

 

I have an auto and 5.13's drove from NJ to TN got 15-16mpg and was cruising between 65-70mph. Every person with any kind of racecar backround freaks out when I tell them I have 5.13's, saying I will have no top end. I have NO problem cruising at 80-85mph, I just do that in NJ lol.

 

well none of them are putting into consideration that your tires are 35" tall. makes a world of difference.

 

I have a 6spd, looks like 513s are the people's choice...what about lockers? If I get lockers in the back, what do you all recommend?

 

Quite frankly "strictly by the numbers" doesn't cut it in the real world. This isn't the first set of gears being put on and there are now lots of installs and lots of real world experience.

But I can give real numbers (all the following speeds, including stock, determined by GPS). Speeds are Colorado's speed limit of 75 MPH. Stock Rubi Automatic with 4.10's and 32 rpm was 2250. BFG 35 KM2's and stock 4.10 gearing rpm was 2050. Same tires with 5.13's installed rpm is 2600.

Does anybody contend that the stock setup, 32"/4.10, is adequate on the freeway? Perhaps in flatlander country but in Colorado it is surely not. It was always coming out of OD and with 35's and 4.10 it was virtually impossible to keep it in OD unless you were dead level or going downhill.

This engine's sweet spot for mileage and power is, from what I have read, between 2400 and 2700. It is my contention that Jeep should have equipped Rubis with 4.56's and not 4.10's. There is no way that 2600 at 75 mph is too fast or too much gear. At that speed or faster the big, heavy unaerodynamic sail we are pushing through the air needs to be making some power.

Finally, before I made the change, I spoke to everybody I could, with actual realworld experience with a JK, about gears. I never came across anybody with 5.13's that wished they had went with 4.88's. Most people who had done 4.88's wished they had done 5.13's. I almost said that nobody who had done 5.10's was unhappy with them, but that's not true; I encounteed a few with 37's or bigger that complained that 5.38's hadn't been available.

I've got aa 98 TJ too. The JK isn't a TJ with a 4.0. The TJ really didn't like a lot of rpm. The 3.8 likes rpm and in fact needs it to perform. Since I've had the gears done I've had it to Moab and the Ouray area and been up to 12,900 ft and it performs great offroad with the 5.13's. Gears are too expensive to make mistakes on. Go with the 5.13's. And that advice comes from both running the numbers and real world experience.

 

I wonder how much experience with gears in a JK your service manager has. With an auto with a .69 OD things change radically. Everybody that hears I put 5.13's in thinks it's nuts. But they are all thinking of old trannys like the Turbo 350.

Off road, with 35's, 5.13's, low range (4:1 Rubi) and in 1st gear the performance is great. It just crawls up and down things in total control. With 35" or 37" tires 5.13 gears are the answer.

 

I agree with you and especially with Chuck45....5.13's is the way to go and you could never convince me I would be as happy with 4.88's. As far as the Service Manager goes...mine was the 1st set of 5.13's they had ever put in a JK and they now recommend nothing less than 5.13's for anyone with 35's or larger.
Like Chuck, I live in Colorado and we definately need 5.13 above 7000ft with 35's. Even if you dont live in CO, if your going to have 35's and will need any sort of highway power (mountains, boats, ATV, etc) you will hate that you did not get the proper gears.

 

ok, got it 513's it is...what about lockers???