What are your stock gears? 3.21's are standard and I'd not be happy with the performance in the NC mountains. If you have 3.73's I'd say you are acceptable. Lots of guys prefer lower gearing with 35's and I'd probably prefer them. But would have to look hard at the cost.

 

I would probably want to run 4.56's with that set up if it's an automatic.

Here's the chart:

 

http://www.wranglerforum.com/f202/differential-ratios-needed-for-different-tire-sizes-1311321.html

^^^Read this!!!!!!!

 

My recommendation is to go with 4.88 gears if you have an automatic transmission. That way you leave yourself open to running 37" tires in the future. 5.12 gears are recommended for a manual transmission. The larger the gear, the more power you'll have at low RPMs. I have 35" tires and an automatic transmission. With 4.88s, I run at 3,200 RPMs at 70 mph. With stock gears I was at 2,400 RPMs. Depending on the gradient, with stock gears (3.21) the transmission will be constantly shifting down to 4th gear. Another thing to consider if you regear is lockers. Regearing isn't cheap. If you add lockers at the same time you'll save money on the installation. The tech has to remove the stock carrier anyway.

 

Based on your scenario as explained - I'll vote 4.56's

 

I would vote 4.88 given your altitude and the weight of the Toyo MTs.
Also IMO go ahead and do the ball joints now too, if they're not worn out from the weight of your Toyos they will be soon.


:hijacked:
Thread swerve:
IMO now would be the time consider an axle upgrade to a 44 or 60 if you wheel a lot. If you don't wheel then don't worry about it.

Your front axle:
Gears $1000
Lockers $500
Ball joints $800 (installed)
$2300

Or a prorock 44 with 4.88, locker & balljoints pre-installed- $3650 then re-gear your rear 44 for say a $1000. With tax, etc you're about a 5k upgrade.
Dynatrac ProRock 44 Unlimited Package (PROROCK44UNL_PKG)

So basically a $1350 upgrade to the MUCH stronger prorock 44

Hope that helps! :thumb:

 

I have 4.10s and 35s. Mountain driving SUCKS. I'm going to 4.56 or 4.88, not sure which yet.

I had a 2013 with 4.88s and 35s, that was fine.

 

If your sticking with 35's go 4.56's. If you think you might go to a 37" one day or add a more weight to the Jeep, I say 4.88's. I would also recommend a master install kit as well!

KOR Gear Packages with Master Install Kits

-Jason

 

If I install anything, my local shop will do it for me. I don't mess with gears. I will absolutely never go to 37s, so you're probably right. I'm just unsure since when I had 4.88s they weren't terrible, but lower RPM is good. I sometimes tow a box trailer, which adds to the load...decisions...

I certainly appreciate your advice on it.

 

Just too throw my 2 cents in,

My Jeep, 2012 JK Sport
6 Speed Manual
3.5" Rubicon Express Short Arm
Pro Comp 35x12.5 Tires
3.91 Gears

Buddys Jeep, 2013 JK Sport
Automatic Trans
3.5" Rubicon Sport Lift
BFG MT2 35x12.5
4.11 Gears

My Jeep with the Manual Trans does so much better on my Jeep with the 3.91 vs my buddies Jeep with the 4.11. His is much more sluggish than mine and his throttle response is way off. At some point, we will both be regearing. I will probably go with 4.56 but we have discussed, because he has the Automatic Trans, he may want to go to 4.88's to compensate for the torque converter. Almost the exact same Jeeps with the same set ups but they feel way different with the 35's Manual vs Auto...

 

It's not the torque converter, it's that the gear ratios are different.

Manual:
1st 4.46
2nd 2.61
3rd 1.72
4th 1.25
5th 1
6th 0.797
Reverse 4.06

Auto:
1st 3.59
2nd 2.19
3rd 1.41
4th 1
5th 0.83
Reverse 3.16

Here's a chart: Jeep Wrangler JK Gear Ratios

 

It's not the torque converter, it's that the gear ratios are different.

Manual:
1st 4.46
2nd 2.61
3rd 1.72
4th 1.25
5th 1
6th 0.797
Reverse 4.06

Auto:
1st 3.59
2nd 2.19
3rd 1.41
4th 1
5th 0.83
Reverse 3.16

Here's a chart: Jeep Wrangler JK Gear Ratios

Correct, but the torque converter in an Auto also plays into this formula due to the slip, but it plays more into the shifting points on an Auto rather than the actual ratios..

Love the chart, that is also great to help assist in choosing based on your set up

 

The slip actually helps as it effectively reduces the gear ratio a bit. Then when not accelerating it locks up to conserve energy and give you the real gear ratio. I don't really know the effective percentage of slip on a modern converter, I haven't touched a tranny since the C6 days.

But I think your plan to go to 4.56 is probably perfect on the manual, as long as you aren't towing. On the other hand, with your steeper final gear, you could go 4.88 and keep the RPM a little lower.

 

The slip actually helps as it effectively reduces the gear ratio a bit. Then when not accelerating it locks up to conserve energy and give you the real gear ratio. I don't really know the effective percentage of slip on a modern converter, I haven't touched a tranny since the C6 days.

But I think your plan to go to 4.56 is probably perfect on the manual, as long as you aren't towing. On the other hand, with your steeper final gear, you could go 4.88 and keep the RPM a little lower.

Agree, no plans to tow at the moment, but was in the back of my mind. For me at the moment, its trying to find that sweet spot as a DD and moderate OR use. But, as everyone else says, if you do it, you will only want to do it once due to he cost....my buddies is in the same boat, with the info we have received and researched, it seems to be the overall opinion for me the 4.56 or 4.88 would work fine, but so far, everyone has pointed him towards the 4.88 or lower since its an auto trans. It really amazes me how different his and mine drive on and off road with the Auto vs Manual with almost exactly the same suspension and tire upgrades. However, I have to admit, we switched off one day doing some moderate OR, in certain circumstances, his was a little easier to navigate certain obstacles than my manual..so I guess each have their ups and downs

 

I have driven around Boone a lot (my sister lives there) with an 09 2dr with 3.73s and I do fine in the area by turning off the overdrive, however, IF I lived there full time, I would regear to 4.88 if it was me.

 

Like others have stated, I like 4.88's for 35" thru 37" for the 3.6 Pentastar with auto trans.
I have 35" BFG KM2 on 4.10's (stock) & it's working fine, but if I were doing a gear change from anything less than than 4.10, it would be 4.88's for best overall performance on & off road (35-37 wise) IMO.

 

The Auto Trans in fluid coupling has got a considerable amount of torque multiplication, effectively greater than that of the manual until the torque converter locks up... This is one of the reasons the newer Diesel trucks are going more and more towards Auto only application. Much greater pulling power off the line or in their case getting a load moving.

 

I have a 2015 jku with 4inch lift and 35 inch tires. I have a spare tire carrier and a 35in spare tire on it. Also my front number is aftermarket (heavy) what gear do you recommend with all that extra weight. It’s really sluggish up hills.

 

I’m dealing with the same issue, I have a 2015 jku, 35 in Toyo MTs 4in lift and front heavy duty bumper, rear tire carrier and spare 35in tire. My keep is sluggish on hills. What gear should I go with since I have all this extra weight plus ppl inside add extra weight.

 

Welcome to the Forum!
Normally with your setup, 4.56. But will all of that added weight, passengers and hill driving, then 4.88 should be a better fit.

 

Another consideration if wheeling is the transfer case gearing. The Rubi's 4:1 seems to come into it's own in 4 low with 35's and 4.10:1 diff gears. Whereas, the 2.73:1 needs 4.56'ds or 4.88's to be coomparable....I find my 2dr Rubi on 35's (ok really 34's as measured on the rig) does very well and I wouldn't want to go lower (or I'd just be wheeling in 4 high all the time!). As it is I'm often in 4th or 5th in places like the Dunes and forest trails I don't see 1st....EVER. Heck, I'll see 3rd before I see 2nd.

 

While it is true that with the Rubi transfer case in 4lo that 4.10's work just fine in most cases most of us regear for the road and 4.10 is not really up for the task.

The general rule for 35's is 4.56 for an automatic and 4.88 for a manual. If you ever are going to think about 37's, live at altitude or tow a lot then going numerically higher is a good idea.

 

Hmmm...I've been running Pat's (which technically run 34" on the jeep in the 315x75x17 variety vs 34.25" in the 35x12.5x18s) and 4.10 stock gears since May of 21 without issue including Montana ghost town hunting at higher elevations and all my trips to our cabin 267 miles away.

Only issue is wheeling in 4 high at altitude.

 

Get back to me when you are doing multi 1000 mile trips a year. To date my record is 7500 miles in 3 weeks.

 

Why? I'm happy as is. It seems everyone wants to tell me I need to do this and I don't see the reason. As for multi 1000 mile trips? Been there done that. Started driving in 1979 and have plenty to of experience to draw from

 

Not in your Jeep. But it is your money. If you are happy more power to you.

 

I just ordered 4.88 for my 2015 with 35’s.

 

@emcvay this is not a competition. You have no more experience than I do or many of people on this site. I found with a manual and stock 4:10 axles to be underwhelming. A moderate hill or head wind has you shifting down to 5th. Once I made the switch to 35's 6th gear became all but useless. Again it was never about off road.

 

I was just responding to you telling me I hadn't made drives of 1000 miles etc etc.

Shifting up or down is the point of a standard. 6th is an overdrive gear and should be treated as such.

I'm far more interested in my gearing when off roading than on road...now, my WRX is a different story.

I drive in a windy place, deserts often are, and I don't need to shift down out of 6th. Hills on the other hand may require downshifting but that's the point of the gears: too allow the driver to keep the revs in the power band as needed.

What you describe is a choice and that's perfectly fine but telling someone they are wrong for saying there is no NEED to regear is not making a statement about choice.

Perhaps I'm just old and used to manuals, after all, I drove my first in the 70s

 

I suppose my prior ownership of a YJ and a TJ keep me confused. I find the power and gearing in my JKU sport with infamous 3.21 gears to be fine with slightly shorter tires than 35's, Dick Cepek Extreme Countrys in 295-70-17 on the highway to be fine. If a hill ever needs a lower gear, I whack the auto shifter to the left and it goes into manual mode and drops a gear. Really the same exact thing as having lower gears in the diffs. I will sometimes drive around town in manual mode to keep the revs higher than the tranny wants to bog down to.