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-   -   3:73 versus 4:10 rear end (http://www.wranglerforum.com/f274/3-73-versus-4-10-rear-end-126778.html)

Shireman 12-09-2011 06:00 PM

3:73 versus 4:10 rear end
 
I ordered a 2012 Rubicon (auto) and it was to have the 3:73 versus the 4:10. The dealer advised me that the vehicle is being built with the 4:10 rear end at their mistake. It is a no cost option at the time of ordering. I have the ability to order another vehicle since it was not our mistake. Can anyone advise me the pros and cons between the two or share actual experiences with the different rears?

It will be my wife's so it will see more highway and hard pavement by far than off road and I would guess the 3:73 would give another mile per gallon better fuel and at higher highway speeds it would not be a loud as the 4:10. I would think the 3:73 with the new engine and trans, the dana's, diff. lock, will still meet any off road challenges. Any thoughts guys? Thanks, Shireman

kjeeper10 12-09-2011 06:14 PM

I think 3.73 is a Rubi is crazy. Why? To save 1 mpg.

Honestly- I don't think it's going make a huge difference.
If your plans are for bigger tires, 4.10's are the way to go.

Resale value/appeal will be better also IMO

basecamper 12-09-2011 06:18 PM

I have read the 1 mpg theory in many threads but have not seen it pan out in real mileage posted. I would read through the mileage threads you will see what i'm referring to. Regarding sound I drove two Rubicons one auto one 6spd both 4:10s and both seemed quiet for Jeep Rubicon's.

ranjr 12-09-2011 06:18 PM

I'd get the 3.73 based on your intended use. I have a '12 Auto with 4.10s and have yet to get better than 17 mpg while a co worker has 3.73s and can get 20. I also would recommend the Sahara for your intended use as the extras the Rubicon offer will be of no use to you on road.

Rubicon_Jim 12-09-2011 06:25 PM

Quote:

Originally Posted by ranjr (Post 1814073)
I'd get the 3.73 based on your intended use. I have a '12 Auto with 4.10s and have yet to get better than 17 mpg while a co worker has 3.73s and can get 20. I also would recommend the Sahara for your intended use as the extras the Rubicon offer will be of no use to you on road.

About the same here. On the highway I get get upwards of 18mpg if I cruise around the 65 mark but on average I'm around 17mpg but I love my 4.10s. As for her use, the 3.73 could net you around 20mpg from what I've seen and is probably a better choice...and honestly, she probably doesn't even need a Rubi.

verdugan 12-09-2011 06:29 PM

Quote:

Originally Posted by ranjr (Post 1814073)
I'd get the 3.73 based on your intended use. I have a '12 Auto with 4.10s and have yet to get better than 17 mpg while a co worker has 3.73s and can get 20. I also would recommend the Sahara for your intended use as the extras the Rubicon offer will be of no use to you on road.

I would caution the OP to use posts like the one above to make a decision. Too many variables here. Are driving styles exactly the same? Are the driving routes/distances exactly the same? My money is that they're not making the comparison useless.

i82much 12-09-2011 06:41 PM

I think the biggest difference in the Rubi mpg vs. Sahara/Sport is the tires, not the gear ratio ...

Still, if you and/or the wife is going to be cranking 80 mph on the highway with regularity for a decade, it may be worth getting the 3.73's. That said I think *most* folks looking for a used Rubi would prefer the 4.10's though.

ranjr 12-09-2011 06:46 PM

Quote:

Originally Posted by verdugan

I would caution the OP to use posts like the one above to make a decision. Too many variables here. Are driving styles exactly the same? Are the driving routes/distances exactly the same? My money is that they're not making the comparison useless.

The same could be said for taking advice from someone who doesn't own a 2012 or has never driven one. The old rule that a Rubicon NEEDS 4.10s has changed with the new 5 speed auto and it's O/D ratio of .83 vs the old 4 speed ratio of .69.

MTH 12-09-2011 06:51 PM

Given your intended use, I think ordering the Rubicon to begin with was foolish.

You're paying an awful lot for electronic sway bar disconnects, selectable lockers, and other serious offroad features that offer no on-road benefit (and may even be on-road detriments) and that sound as if they'll never be used.

Rubicons should come with 4.10s. It's part of their offroad capability. I'd take it that way and just toss them on the list of capabilities you've overordered. You might as well be "all in."

Ordering 3.73s is like asking them to put street tires on it, IMO.

tomthbomb 12-09-2011 06:54 PM

The gearing difference between the 3.73 and the 4.10 is 10%.

The MPG difference between the 3.73 and the 4.10 is around 10%.

Funny how that works out. Karma? No mathematics.

If you need 10% lower gearing for bigger tires in the future go with the 4.10.

If you need 10% better MPG now go with the 3.73.

i82much 12-09-2011 06:55 PM

Quote:

Originally Posted by ranjr (Post 1814144)
The same could be said for taking advice from someone who doesn't own a 2012 or has never driven one. The old rule that a Rubicon NEEDS 4.10s has changed with the new 5 speed auto and it's O/D ratio of .83 vs the old 4 speed ratio of .69.

Ok but ... do you understand how mathematically these gear ratios work? The new transmission has "less" overdrive. In other words:

4 speed, 4:10's at .69 = 2.829 final drive ratio.
5 speed, 4:10's at .83 = 3.403 final drive ratio.

If anything about the new trans weighs against getting the 4.10's, it is the steeper first gear and not the "shorter" (numerically larger) overdrive.

JIMBOX 12-09-2011 06:57 PM

:whistling: With any size tire, up to 37"--there's only about 200 RPM difference between the 3.73/4.10 gears--at 70mph

If I was gonna get another Rubi--I'd stick with the 4.10s--stick/auto, any difference in gas mileage is determined by the DRIVERS HABITS/TERRAIN !!

200 rpm has no significant effect, on an engine that runs between 700 and 6000 rpm !!

Keepyerpowderdry

:dance::rofl: JIMBO

Matador 12-09-2011 07:01 PM

Is 4:10 the standard option on Rubicons with automatic transmission? The dealer went ahead and ordered the jeep without me being there and I didn't specify that I wanted 4:10. I can double check with him in the morning but I just wanted to make sure

i82much 12-09-2011 07:01 PM

Quote:

Originally Posted by tomthbomb (Post 1814157)
The gearing difference between the 3.73 and the 4.10 is 10%.

The MPG difference between the 3.73 and the 4.10 is around 10%.

Funny how that works out. Karma? No mathematics.

If you need 10% lower gearing for bigger tires in the future go with the 4.10.

If you need 10% better MPG now go with the 3.73.

Technically speaking, it's not even close to that simple. Not. Even. Close.

ESP 12-09-2011 07:02 PM

Quote:

Originally Posted by JIMBOX (Post 1814162)
:whistling: With any size tire, up to 37"--there's only about 200 RPM difference between the 3.73/4.10 gears--at 70mph

If I was gonna get another Rubi--I'd stick with the 4.10s--stick/auto, any difference in gas mileage is determined by the DRIVERS HABITS/TERRAIN !!

200 rpm has no significant effect, on an engine that runs between 700 and 6000 rpm !!

Keepyerpowderdry

:dance::rofl: JIMBO

Hold up there kemosabee, a rubi is pushing more weight around than other models in addition to the lower gears. Driver habits DO make a big difference but regardless of driver, he/she has to drive a jeep with or without lockers, LSD, manaul or auto, front-rear D44s, MTs...etc all of which affect MPG

kjeeper10 12-09-2011 07:13 PM

Think most agree 4.10's benefit the Rubi

ranjr 12-09-2011 07:13 PM

Quote:

Originally Posted by i82much

Ok but ... do you understand how mathematically these gear ratios work? The new transmission has "less" overdrive. In other words:

4 speed, 4:10's at .69 = 2.829 final drive ratio.
5 speed, 4:10's at .83 = 3.403 final drive ratio.

If anything about the new trans weighs against getting the 4.10's, it is the steeper first gear and not the "shorter" (numerically larger) overdrive.

What?? The 2012 Auto with 4.10 rear is comparable to the 4 speed with 4.88s when in O/D. I completely understand the differences. It all depends on what you need; a highway Jeep or an off-road Jeep.

i82much 12-09-2011 07:21 PM

Quote:

Originally Posted by ranjr (Post 1814200)
What?? The 2012 Auto with 4.10 rear is comparable to the 4 speed with 4.88s when in O/D. I completely understand the differences. It all depends on what you need; a highway Jeep or an off-road Jeep.

I see, and I am sorry for suggesting you misunderstood the math. Since the OP seemed concerned that the 4.10's were too steep (bad mpg or whatever) I didn't see how the new trans OD would help alleviate that concern.

I gather you were coming at it from a different perspective, e.g., more gear is "better" from a power perspective.

jk'n 12-09-2011 07:28 PM

I had both a Sahara Unlimited 3.73 and a Rubicon Unlimited 4.1 in the 2008 model. The Sahara in 11/07 and got the Rubicon in 8/08. Both were quiet and have excellent road manners. I average about 2.5 mpg less in the Rubi. I tow a trailer near the load limit of the Unlimited of 3500 lbs. The Rubicon is way better doing that. The post above that says it doesn't matter in the 2012 probably doesn't understand low gear torque capability...I'm guessing. Another advantage of the lower gearing besides low gear torque is the ability to be able to crawl in 4 low. I use my jeep both on road and off and I can't tell you what difference the Rubicon has made just in confidence when in tricky situations. I like to know that I have all of those tricks up my sleeve when I need them.

This all being said, if you don't intend to tow or go off road, the difference in price between the Sahara and Rubicon doesn't seem to be justified.

kik 12-09-2011 07:36 PM

Since you already decided and ordered a Rubi then you should thank the dealer for their "mistake". If you get a do-over, maybe you should consider a loaded Sahara for what you really want to do with it. If you decided to continue with the Rubi then the 4.10's are a good thing.

kjeeper10 12-09-2011 07:40 PM

Should have a choice of 4.10 PLUS
Don't understand the 3.73 option :confused:

ESP 12-09-2011 07:42 PM

Quote:

Originally Posted by kjeeper10 (Post 1814295)
Should have a choice of 4.10 PLUS
Don't understand the 3.73 option :confused:

Was thinking the same. Why in the world would they offer those on a rubi?

JIMBOX 12-09-2011 07:44 PM

:whistling: I don't know what you're talking about-


Quote:

Originally Posted by ESP (Post 1814171)
Hold up there kemosabee, a rubi is pushing more weight around than other models in addition to the lower gears. Driver habits DO make a big difference but regardless of driver, he/she has to drive a jeep with or without lockers, LSD, manaul or auto, front-rear D44s, MTs...etc all of which affect MPG

There may be 100lbs difference between a Sahara/Rubicon--STOCK, but

You get 10 different familys driving with kids/passengers/camping gear, lunchs/ golf gear and you range from (JKU) 4200 lbs to 5000 lbs--it just ain't as simple as a 200 rpm difference between 3.73/4.10 making a difference and

Not only that, but the 4.10 gears give a jeep a much wider playground, for tire size experiments--AT NO COST !

:dance::rofl: JIMBO

panthermark 12-09-2011 07:48 PM

Quote:

Originally Posted by ESP (Post 1814303)
Was thinking the same. Why in the world would they offer those on a rubi?

My guess is because there are a zillion out there that will stay stock and never leave the pavement...especially when you consider the gearing of the new tranny.

People come in and want to buy the top of the line Rubi...and Jeep is happy to sell it to them.

CAFE

blackforestgreen 12-09-2011 07:48 PM

i had a 2003 dodge 3500 cumins 4x4 with 3.73 rear, which was totaled, and replaced with a 3500 cumins 4x4 with the 4:10 rear, didn't feel much of a difference, nor any significant mpg change.

i now own an 08 sahara jku and a 12 wrangler sport, both 3.73 gear ratio, both auto. the 3.73 is more than enough for the new rubis, and i don't think you will notice much of a difference in day to day driving between the two ratios. if it comes through with a 4.10 and it has everything else you want i would take it. drive it first for a test spin and then test another on the lot with the 3.73 and then decide for yourself. there is some thought to be given to the rubicon vs sahara, you will spend money on things you may never use, but i bet you will,
and the rubi will have a higher resale.
for you guys that know more than i do about gears, if the op takes the 4.10 ratio, can't he put on some larger diameter tires and essentially bring the ratio down to to act the same as a 3:73 or lower? congrats on the new jeep.

ranjr 12-09-2011 07:53 PM

This is why I don't recommend the 4.10s for a mostly highway driven Jeep.

Attachment 82314

That's 80 mph in O/D with the ECO light on at 3000 RPM. I got 15 MPG on that trip at that speed.

All the following are in O/D in a '12 Rubicon Auto with 4.10s and stock tires:
80 - 3000 rpm
70 - 2600 rpm
55 - 2000 rpm

If you're staying with 33 inch tires or smaller, I recommend the 3.73s with the '12 Auto. Anything bigger, 4.10s.

kjeeper10 12-09-2011 07:53 PM

Quote:

Originally Posted by panthermark
My guess is because there are a zillion out there that will stay stock and never leave the pavement...especially when you consider the gearing of the new tranny.

People come in and want to buy the top of the line Rubi...and Jeep is happy to sell it to them.

CAFE

Curious to see how many Rubi's hit the used lots with 3.73.
Will it effect the value ?
Don't see any rubi's ordered with 3.73.
(besides this one)
Hard sell if the buyer knows any better.

panthermark 12-09-2011 08:01 PM

Jeep should give you an option at order.
3.21 (for CAFE), 3.55, 3.73.....plus 4.10, 4.56 for the Rubi's so people can go with 35's or maybe even 37's right off the bat.

I would KILL for factory 3.55's.

blackforestgreen 12-09-2011 08:15 PM

Quote:

Originally Posted by kjeeper10 (Post 1814340)
Curious to see how many Rubi's hit the used lots with 3.73.
Will it effect the value ?
Don't see any rubi's ordered with 3.73.
(besides this one)
Hard sell if the buyer knows any better.

KJ what year is your jeep? at the dealer i bout my sport from, all the rubicons were 3.73.

i82much 12-09-2011 08:16 PM

So I think Ranjr's point is that you are getting more gearing already in the '12 auto because the gear ratios are all shifted "down" or to be relatively "steeper" than in the 4 speed auto. So you're getting that gearing from the trans instead of the axle.

Another way of looking at it is to say that a '12 auto with 4.10's has more "gear" than an '11 auto with 4.10's.


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