[shep546]

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

 

[shep546]

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

I have 3.21's so I'm definitely regearing... problem is I live in Canada with a small population so the chances of finding a used rubicon Tcase is literally impossible...

Where are you getting your data from? 4.88s at 70mph is that RPM in 6th gear?

 

[shep546]

So I really want to go with 4.88s but even with the cryo treatment I'm worried it's too much to stuff into a dana 30... really don't wanna blow up my $1200 locker