matt852

Wondering what gearing you guys went with. Going more for a specific type of build running 35's, lots of highway but will be installing an atlas 4 speed T-Case shortly to make up for the "highway gearing".

My 315 STT Pros which are technically a 34.6 actually measure 33.5 inches. I drive a lot of highway going 75-80 on the interstate to California from AZ.
So far I have narrowed my choices down to 4.56 and 4.88 gearing. When I replace my tires I will go again with the same tire STT PRO which is a lighter "35" that actually only measure 34 when new mounted at 28 psi.

Here's my loadout with the significant weight added from stock form:
Winch 60lbs
Rock Rails 77lbs
Front Bumper 55lbs
Rear Bumper 50lbs
Rock Krawler 8 Control arms ~80lbs forgot the weight of the stock control arms
5 Cooper Stt Pros 66lbs each tire

I have heard both 4.56 and 4.88 to get good gas mileage at 75 mph but most of the guys with 4.88 don't run at 75mph+.

Thanks,

Matt

shabbernigdo

on my jeep i have 35's that measure right at 34 with 30 psi and at 75 im doing about 2600 rpm with 4.56

jtphoto JK

According to the 3.8L gear charts 4.56 on 35 with 3.8L 6spd will put you at 2,575rpm at 70mph. That might be a bit steep for running 80mpg. 4.10 will put you at 2,316rpm so You may be better off with 4.10 for your application ...

TheDirtman

How is the 4 speed atlas going to make up for "highway gearing"? With 35's I really don't see the reason for a transfer swap unless you really want twin sticks. I really don't see someone on 35's needing and atlas let alone the 4 speed which with 35's is going to be going so slow you might fall asleep wheeling with it.

matt852

I'll have the one with 2.72, 3.8 and 10.3. So for the really nasty stuff use the 10.3, ok light stuff 3.8. I don't really mind crawling very slowly if needed.

Mark Doiron

At 208,000 miles on my Jeep, all over the U.S. (been to three of four corners and Alaska), having driven it from the Mexican border to the Arctic Ocean, I have quite a bit of experience with highway driving. 4.88s, 35s, very heavy (approaching 7K pounds). I guess "good gas mileage" is a matter of opinion. I generally keep my speed to 65 and below and, without wind and hills (honest, it's uphill both directions the roads I travel sometimes!) I get in the low-mid teens. I'm turning about 3K RPM at 70 MPH. Sometimes I go 75 MPH, but only very rarely faster (just briefly to pass). MPG drops a mile or two when I go that fast, and can even drop into single digits if the wind is against me.

jtphoto JK

I am not up on my TC gearing but from what I understand in 2 and 4 Hi the factory TC is 1:1 is it not? If the Atlas doesn't give you this option you may not be able to do 80mpg.

TheDirtman

10.3: will very rarely be used because it is just too slow and your tires are just going to be too small to take advantage of the low crawl speed. 3.8 is what you will be using 90% of the time off road even on the hard stuff. and if you want to go a bit faster off road the 2.72 is an option but also rarely used. Save some weight and money and just do a 3.8, 4.3, or 5.0 2 speed.

jtphoto, you are correct that the atlas will do nothing for highway expect for some extra noise that the gears make vs a chain drive like the factory box.

kevinlee

My MTZs measure at 34.25. I have stock rubi 4:10s and at 75mph I am running 3000 rpm. Gas mileage on the highway averages about 15mpg. It gets better or worse depending on wind direction.
I drive 160 miles mostly highway every other Sunday. I can get up to speed ok on the on ramps if I am heavy on the gas. But I can only use 6th gear if it is flat or down hill. I cannot maintain 75 going up most hills with out down shifting to 5th.

Over it's ok not ideal but it works well enough that I am not regearing unless I go up to 37s. Lacks enough that I would not recommend 4:10s to someone regearing.

matt852

Yes my plan was to go with a higher gearing 4.56 instead of the 4.88 for on road highway and then make up for my offroad ratio with the low range options of the atlas TC. The TC upgrade I was planning for offroad and the higher gear set (lower numerical value) for highway.