Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of JUNE's Ride of the Month Challenge!

1 - 20 of 47 Posts

·
Registered
Joined
·
472 Posts
Discussion Starter · #1 ·
I am adding a Detroit True-Trac very soon to the front pumpkin and since I'm almost 60, I think I will stay with the 32" tires. I have the auto tranny and I wonder what advantage I would gain with swapping to 4.10 gears over what I have besides a modest boost in off-roading ability. Since my JKU will reach overdrive quicker, you reckon I will get about the same mileage I'm getting right now, which is an averaged 17.5 mpg? I imagine a Rubi owner can answer this one fairly easy. BTW, I am a very modest driver when it comes to mashing the go pedal.
 

·
Registered
Joined
·
8,554 Posts
4.10s would be a waste. You'll want at least 4.88s and possibly even 5.13s. Along with a ProCal, the result will be substantially more power, especially on the highway. You'll actually be able to pass people going uphill, OD will be useful, etc.
 

·
Registered
Joined
·
9,914 Posts
:whistling: Interesting--

So as the AGE goes up---the TIRE SIZE goes down-huh !

What manual are you reading, or ???

:dance::rofl: JIMBO
 

·
i'm back
Joined
·
13,706 Posts
:whistling: Interesting--

So as the AGE goes up---the TIRE SIZE goes down-huh !

What manual are you reading, or ???

:dance::rofl: JIMBO

i can see this thread going downhill quickly! :rofl:

-bob :nonono:
 

·
Registered
Joined
·
166 Posts
uhh no. you will be fine with 3.73's. 4.13's would be a nice little upgrade but im not sure if it would be enough of a difference to tell. i dont think it is necessary. but at the same time while you have it apart why not.
 

·
Registered
Joined
·
472 Posts
Discussion Starter · #7 ·
I installed the 2.5 inch Teraflex lift and my wife is very short, so climbing up into the Jeep is already a task and I have short legs to boot. If I go up in tire size, it will be harder for her to get in... Why am I having to answer these questions? This ain't my first rodeo. :flowers:
 

·
i'm back
Joined
·
13,706 Posts
I installed the 2.5 inch Teraflex lift and my wife is very short... Why am I having to answer these questions? This ain't my first rodeo. :flowers:
because for some retarded reason Jeepers love to screw with each other... we need something to amuse ourselves! :angel:

-bob
 

·
Registered
Joined
·
472 Posts
Discussion Starter · #9 ·
That's a good answer. I live on the very flat Gulf Coast of Texas, but we are thinking of driving the Jeep to California to see the Redwoods. Running a low fricking gear like 5.13's may make it a heckalot better for climbing the rocks at the Exxon gas station, but would screw up my mileage terribly for distance driving. I'm still wondering what Rubi's get with 4.10's and 32 inch tires as far as gas mileage goes. :flowers:


uhh no. you will be fine with 3.73's. 4.13's would be a nice little upgrade but im not sure if it would be enough of a difference to tell. i dont think it is necessary. but at the same time while you have it apart why not.
 

·
i'm back
Joined
·
13,706 Posts
lots of guys are in the high 18-20 mpg range. don't forget to recalibrate your speedo if you change gear ratios...

you're right, you definitely don't need a 5.13, but i would bet a 4.88 would be a better bet than the 4.10. gives you more versatility... (if you decide to go bigger with tire size) if you decide to sell it....

-bob
 

·
Registered
Joined
·
472 Posts
Discussion Starter · #11 ·
Well, truthfully, I am vacilating between 4.56's and 4.11's or just sticking the True-Trac in for now. Looking at the gear chart, going into the green is tempting. 4.88's may be the ticket, like you say.
 

·
Registered
Joined
·
8,554 Posts
I need 5.13's to drive on the freeway on 32 inch tires with a 4 speed automatic???
No you don't "need" to do anything to your gears.

However, your pre-2012 4 speed auto is in fact terribly undergeared. How undergeared? Well, a stock pre-2012 MANUAL trans Rubi spins about 2500 RPMs at 70 mph in 6th gear (which is the manual trans's OD).

Do you know what gear ratio you'd need in your 4 speed auto to spin about 2500 RPMs at 70 mph in 4th gear (which is your OD)? You'd need something between 4.88s (about 2400 RPMs at 70 mph) and 5.13s (about 2600 RPMs at 70 mph).

Therefore, in order to have as much "pep" on the interstate as a STOCK pre-2012 manual Rubi, you should regear to 4.88 or 5.13 even on your stock tires. Put another way, you'd only be spinning a little more than a "stock level" of RPMs even if you went to 5.13 gears. 4.88s would actually be below "stock levels."

By contrast, right now you're spinning about 100 LESS RPMs at 70 mph than a manual trans with the lowly 3.21 gears at the same speed. Regearing to 4.10 would put you about 100 RPMs higher than that, which is hardly going to be "worth it" in my opinion.

There are some folks on this forum with pre-2012 autos that have regeared to 5.13 with stock tires. Haven't heard any complaints yet. Up to you.
 

·
Registered
Joined
·
472 Posts
Discussion Starter · #13 ·
Okay, well, that makes a strong case for me to go with 4.88's then even with 32's. God help me if I decided to run 37's, I'd have to buy a whole new Jeep. Ha ha!
 

·
i'm back
Joined
·
13,706 Posts
Okay, well, that makes a strong case for me to go with 4.88's then even with 32's. God help me if I decided to run 37's, I'd have to buy a whole new Jeep. Ha ha!
nah... half the fun in owning one is changing everything.. twice!
:D
 

·
Registered
Joined
·
8,554 Posts
Okay, well, that makes a strong case for me to go with 4.88's then even with 32's. God help me if I decided to run 37's, I'd have to buy a whole new Jeep. Ha ha!
No no, just swap in a Hemi. :D
 

·
i'm back
Joined
·
13,706 Posts

·
Registered
Joined
·
29 Posts
I’m probably repeating what others have said, however I agree that 4.10 and 3.73 are so close it isn’t worth the swap, so I’d at least go with the 4.88s
 

·
Registered
Joined
·
8,554 Posts
So, what gear ratio/tranny are you running and what kind of mileage do you average?
I have the aforementioned "lowly 3.21s" on 33x12.5R15 DuraTracs in my 2010 JKU with 2.5" TeraFlex coil lift.

However, I also have a manual transmission. So I solve my RPM "problem" by just never--ever--using 6th gear. As a result, I spin about 2400 RPMs at 70 mph in 5th gear, which is about what you'd spin on 4.88s.

I drive about 80% highway and average about 18.5 to 19.5 mpg.
 

·
Registered
Joined
·
29 Posts
I have the aforementioned "lowly 3.21s" on 33x12.5R15 DuraTracs in my 2010 JKU with 2.5" TeraFlex coil lift.

However, I also have a manual transmission. So I solve my RPM "problem" by just never--ever--using 6th gear. As a result, I spin about 2400 RPMs at 70 mph in 5th gear, which is about what you'd spin on 4.88s.

I drive about 80% highway and average about 18.5 to 19.5 mpg.
It is nice to have “six-gear ratios” with the manual, lol!! Heck you could still grab 6th going downhill on the highway.
 
1 - 20 of 47 Posts
Top