My review of 5.13 gears with 33's and 42RLE
- Thread starter NKlekas
- Start date
Comes down to some details about your jeep and your intentions for it.
I’d rather rev a little high than a little too low (that’s where preference comes in).
I’ve driven the jeep on the highway with OD off revved from 3k to 4K (trying to fix a sticky lifter) and found that anything in the 3,300 range and a little higher seems super happy still and engine temps were good to go. So I’d definitely go deeper than taller if I’m on the edge. But again, I’m not doing 85+ on the freeway ever so I can get away with that.
The only way you can possibly know that it is great is to have run other ratios and go back to 4.56 because the others weren't so good. You simply don't know what you don't know.
Ok, point taken. So I just bought another LJ, this time an 06 Rubicon. I would like to run 35s on it as well. If I went 513s what would I notice different? Would I lose top end? A little faster off the line?
One other thing, if I switch out the gears can I keep the factory lockers? When I did my first LJ we put lockers and 4.56s at the same time so I'm not sure.
We're talking about one of your Rubicons with the original lockers right? If so you can go to a lower ratio like 5.13 or 5.38 by using a "thick" R&P gearset like from Revolution Gear. The thicker ring gear allows it to reach the smaller diameter gear head of the lower ratio pinion gear.
What size tires are you running? For 35's and automatic transmission on a Rubicon I'd go strictly for 5.38. For others with a non-Rubicon, 5.13 is as low as you can regear to with the factory front Dana 30.
This is what I installed for my automatic-equipped Rubicon.
I am running 35s on my auto LJ with 4.56's. Put I did put an aftermarket 44 in front before I did. When I do the new(to me) LJ Rubi. I will go 5.13s. It's going in the shop next week for a metal cloak Game Changer 3.5 inch lift. Then gears and 35s and I don't think I'm going to do anything else to it.
So just to be clear you are saying I can keep my factory Rubicon lockers even when I go to the 513s or 5:38s?
That's exactly what I said above and showed you the boxes they came in. And for 35's you DEFINITELY want to go with 5.38, not 5.13. Even 5.38 is barely enough gear for cruising on the highway at 65-70 mph when you have the 42RLE automatic with 35's.
Whatever improvements the 4.56s did for you, and that 5.13s would do for you, the 5.38s improve it even more.
If you want RPM data at different speeds with your set-up, use the drop-down menus to select your Transmission & XFR case, and then enter your tire size & gear ratio into the Grimm Jeeper website. The data supports the 5.38 suggestions you are getting in here.
You aren't gaining anything by not going to 5.38s when you have 35s with a 42RLE and front Dana 44.
For a visual, below are some results with 5.38s, 5.13s, and 4.56s with 34.5" tires.
5.38s
5.13s
4.56s
Ok, thanks. 5.38s it will be. Since he's going to have it all apart how do you feel about going to rcv axles while he's in there?
akajibio
TJ Enthusiast
Very nice write up and photos with references to past and present scenarios. However, this idea of "the right gear" is still very subjective, in my opinion. Personally, I would hate to drive 70mph with rpms near 4000. But your Jeep your choice! Enjoy the ride.
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