[lee indy]

Hey guys,

2014 JK running 35x12.5x15 mtrs with kevlar.

I am regearing, adding lockers and gusseting/trussing both my dana 30 & 44.

I am stuck on my gear ratio right now... I do a lot of crawling and wanted the lower gearing but I am concerned about stuffing 4.88 into the dana 30?

Would I be safer with the 4.56? I have a 6 speed and am mostly just concerned with being able to crawl over stuff without much gas.

Thanks

if your only concern is crawl then 4.88 will get you a lower crawl but will sky rocket your cruizing rpms

HONESTLY the best way to do that if your staying with 35s is to swap your tcase for a rubi case. Im running 4.56 gears on 37s manual trans and 3.6 runs out perfect but i have a rubicon so my crawl ratio is stupid low already. I wouldnt regear on 35s unless you are on 3.21. if you are running 3.21 id go with a 4.56 just in case you ever want bigger. if on 3.73 id leave em and swap to a rubi case for about the same money as a regear if not cheaper.

with 4.88 you will be turning 2600rpms to do 70mph
with 4.56 you will be turning 2400rpms to do 70mph
with 3.73 you will be turning 2000rpms to do 70mph


conversely you care about your crawl ratio so ill put that on here too

with 3.73 and a sport case you will have 45-1 crawl ratio and 1st gear 750rpms will take you 152 fpm

with 3.73 and a rubi case you will have a 66-1 crawl ratio and 1st gear 750rpms will take you 103 fpm

with 4.56 and a sport case you will have a 55-1 crawl ratio and 1st gear 750rpms will take you 125 fpm

with 4.88 and a sport case you will have a 59-1 crawl ratio and 1st gear 750rpms will take you 117 rpm


and for reference
my jeep on 37s with a rubi case and 4.56 gears has a crawl ratio of 81-1 and does 89 FPM
I use 1st for low speed crawling where I hardly ever use the gas. plenty of torque available. My second gear will do 153 fpm and I use it more for easy cruising over rough terrain.

So if crawl is your concern then swap the case. if you dont like the day to day drive and want a little more launch of the line. Id go 4.56 the extra little bit of slower crawl out of 4.88 would not be enough for me to justify turning 2600rpms on the highway

 

[lee indy]

Gear Ratio Calculator

you have a nsg370 wide ratio trans and a np241 tcase.

yep thats in 6th at 70 mph no kph

 

[lee indy]

yeah. and the calculator says you would be turning 2722. but you probably arent actually running a true 70.

my speedo was off bad from the factory (like 5mph at 70 stock) when i calibrated it i cal'd it at 70 and ended up punching in a 35.5in tire into the flash cal when im on 37s to get it to read dead on at 70

 

[lee indy]

There's a selector at the top to switch between SAE and metric so you can choose between MPH and KPH.

Neat. never had a need for that so I never noticed it. :beerdrinking:

 

[lee indy]

I may end up going with an Atlas instead.

my rubi case will be for sale one day. problem is the Atlas one i want is $$$$$

 

[lee indy]

That's because almost no tire in existence measures as big as the advertised size. It's the difference between what the specs are on paper and the way things actually work in the real world.

If you put in the actual real world rolling diameter of your tire the calculator is spot on. If you insist on using published specs instead, you'll be off. Garbage in, garbage out.

Yep. there is that too. my MTRs were like a 34.5 mounted but they looked huge next to the same size km2. witch was closer to a true 34. my 37s look big but they are probably a 36.25 in reality. the 13.5 width makes them look monstrous

 

[lee indy]

yeah same here. i love the calculator it gives much better info than those stupid charts everyone has.