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-   -   Help me understand the 3.73 vs 4.10 axle ratio (http://www.wranglerforum.com/f274/help-me-understand-the-3-73-vs-4-10-axle-ratio-110020.html)

penberth 08-29-2011 06:24 PM

Help me understand the 3.73 vs 4.10 axle ratio
 
I am trying to make sure that I understand this. So if you get a 2012 Wrangler Unlimited with an Auto Tranny, it comes standard with the 3.73 axles ratio, even though under the standard equipment section of the window sticker it lists the 4.10 axle ratio.

And it really only has the 4.10 axle ratio if it lists it under the optional equipment with the $50 charge.

Is this correct?

So if I find an Unlimited Rubicon and it doesn't show a $50 charge for the axle ratio, I should assume that it has the 3.73 axle ratio, right?

Bryan

panthermark 08-29-2011 06:47 PM

Quote:

Originally Posted by penberth (Post 1520291)
I am trying to make sure that I understand this. So if you get a 2012 Wrangler Unlimited with an Auto Tranny, it comes standard with the 3.73 axles ratio, even though under the standard equipment section of the window sticker it lists the 4.10 axle ratio.

And it really only has the 4.10 axle ratio if it lists it under the optional equipment with the $50 charge.

Is this correct?

So if I find an Unlimited Rubicon and it doesn't show a $50 charge for the axle ratio, I should assume that it has the 3.73 axle ratio, right?

Bryan

For 2011 the 3.73 was standard with the auto JKU's
For 2012, the 3.21's are standard on the auto JKU's (Sport and Sahara), and it is $50 for 3.73's.
Only the Rubi can have 4.10's, and it is $50. Also, for the Rubi, 3.73's are standard.

Everything that you have read about gearing on these Wranglers has been tossed on its ear in regards to the 2012 auto's because of the engine, and more importantly, the new tranny.

Best way to put it..... Depdending on the speed, 3.21's on a 2012 auto are almost like 4.10's on a 2011 auto.

4.10's on a 2012 auto probably like 4.88's or lower (numerically higher) on a 2011 auto.

jk wrangler fan 08-29-2011 08:56 PM

Would anyone know the conversion ratio for a 2012 5 speed auto if equipped with 3.73's? Meaning, if the 4.10's would be equivalent to a 4.88 due to the 5 speed different ratios would the 3.73 fall in the 4.4x range?

penberth 08-30-2011 10:48 AM

Quote:

Originally Posted by panthermark (Post 1520328)
Only the Rubi can have 4.10's, and it is $50. Also, for the Rubi, 3.73's are standard.

So should I assume that the Rubicon Unlimited only has the 4.10 gears if I see it listed in the Optional Equipment section of the Window Sticker?

If it isn't there under the Optional Equipment section, even though the 4.10 is listed under the Standard Equipment section, the Rubicon will have the 3.73 gears, right?

Bryan

panthermark 08-30-2011 12:29 PM

Quote:

Originally Posted by jk wrangler fan (Post 1520639)
Would anyone know the conversion ratio for a 2012 5 speed auto if equipped with 3.73's? Meaning, if the 4.10's would be equivalent to a 4.88 due to the 5 speed different ratios would the 3.73 fall in the 4.4x range?

You can thank Up HIill Bill for the link...this is a pretty good tool.
Gear Ratio Calculator

3.73's on the new auto tranny are a lot like 4.56's on the old tranny.

But keep in mind, there are two moving targets. One is just the gearing ("x" RPM at "x" speed and vice versa), the other engine power at "x" RPM.

panthermark 08-30-2011 12:32 PM

Quote:

Originally Posted by penberth (Post 1522716)
So should I assume that the Rubicon Unlimited only has the 4.10 gears if I see it listed in the Optional Equipment section of the Window Sticker?

If it isn't there under the Optional Equipment section, even though the 4.10 is listed under the Standard Equipment section, the Rubicon will have the 3.73 gears, right?

Bryan

For a Rubi.....if it says 4.10 anywhere on the window sticker....it should have 4.10's. If it does not, I would assume it has 3.73's. I should ask...(can't remember if this matters)....auto or stick?

Up Hill Bill 08-30-2011 12:39 PM

Quote:

Originally Posted by penberth (Post 1520291)
So if I find an Unlimited Rubicon and it doesn't show a $50 charge for the axle ratio, I should assume that it has the 3.73 axle ratio, right?

Bryan

For $40K, don't assume anything!

Ask the dealer for the build sheet (not the window sticker), it is the final word. It will tell you exactly what is on that particular Jeep. The dealer can get it quickly and easily. If they won't get it for you, shop elsewhere.

Lighting Guy 08-30-2011 12:42 PM

I could be wrong, but I think the 4.10's are listed as standard, because they ARE standard with a manual... which is also standard. It is when you change the tranny to auto, that it brings the gears down to 3.73, unless you add it separately for $50. (and maybe with a tow package, that part I can't confirm, dunno if anyone can, haha.)

panthermark 08-30-2011 12:56 PM

Quote:

Originally Posted by Lighting Guy (Post 1523051)
I could be wrong, but I think the 4.10's are listed as standard, because they ARE standard with a manual... which is also standard. It is when you change the tranny to auto, that it brings the gears down to 3.73, unless you add it separately for $50. (and maybe with a tow package, that part I can't confirm, dunno if anyone can, haha.)

^Yup....I think that is it.
4.10's are standard when you set the standard manual Rubi.
3.73's are standard when you get the optional auto Rubi.

Comac90 08-30-2011 01:00 PM

Quote:

Originally Posted by panthermark (Post 1523082)
^Yup....I think that is it.
4.10's are standard when you set the standard manual Rubi.
3.73's are standard when you get the optional auto Rubi.

Correct ...

That said ... Didn't all (manual and auto) Rubicons that hit D1 before 7/6/11 get 4.10s as standard (unless you had them changed like UpHillBill)?

T

penberth 08-30-2011 01:07 PM

Quote:

Originally Posted by panthermark (Post 1523082)
^Yup....I think that is it.
4.10's are standard when you set the standard manual Rubi.
3.73's are standard when you get the optional auto Rubi.

I am looking at a Rubi with Auto Tranny.

This is what I thought, but just wanted to confirm it. I will also ask for a build sheet.

I guess I need to figure out if the 3.73s would be fine, or if I hold out for the 4.10s.

JohnT11 08-30-2011 04:51 PM

Quote:

Originally Posted by penberth (Post 1523115)
I am looking at a Rubi with Auto Tranny.

This is what I thought, but just wanted to confirm it. I will also ask for a build sheet.

I guess I need to figure out if the 3.73s would be fine, or if I hold out for the 4.10s.


Depends on what you want to do with the Jeep. If you're just going to drive it around on the street, I doubt you'd be unhappy with 3.73s. If you're going off-road, hold out for the 4.10s.

Comac90 08-30-2011 07:35 PM

Quote:

Originally Posted by penberth (Post 1523115)
I am looking at a Rubi with Auto Tranny.

This is what I thought, but just wanted to confirm it. I will also ask for a build sheet.

I guess I need to figure out if the 3.73s would be fine, or if I hold out for the 4.10s.

There are a couple of recent threads on this ...

The quick answer is do 4.10s and be done with it. :thumb:

Most, will want 4.10s because it's peppier off the line. For 'me' (and I'm in the minority), 4.10s with the auto, 4 to 1 T-case, and stock 32" tires is geared too low in my opinion. 1st gear, low range can be un-usable in low traction situations ... and I'm willing to sacrifice on-road peppy-ness for off-road ability, so if I was staying stock, I'd do 3.73s. .... or better yet, just get the manual with 4.10s - then your problem is solved.

That said, I didn't stay stock :D ... with the new auto, 3.73s and the stock 32" tires, final drive calculates out to nearly the exact same as 4.10s with 35" tires. :thumb:

point: if you're increasing tire size at any time in the future, opt for the 4.10s.

Up Hill Bill 08-30-2011 07:47 PM

^^^ Comac90 pretty much hit it square on the head. I'm not going to lift and will go no larger than 33" tires. The 2012 auto with 3.73s is geared plenty low! Very peppy, Loves climbing hills! Perfect match with stock tire size.

If your going to go to 35" tires, get 4.10s. If your going to tow max loads on steep grades at altitude, get the 4.10s. If your building a dedicated rock crawler with big tires, 4.10s might not be low enough.

panthermark 08-30-2011 08:35 PM

^^^Agreed with both of the above. It is one of the reasons why I keep going back and forth between 3.21's and 3.73's since this will be my daily driver (with a lot of highway miles) with very light off-roading since I'm looking at an auto. I think the 3.73's might be a tad low for my particular use (strictly because of highway travel)....but they are very good option for most Wrangler's out there.

MrMagoo 09-26-2011 01:39 AM

Very misleading window sticker. I think it would it be a reasonable conclusion to think you were getting the 4.10 if that were the only ratio listed. I wonder how many potential owners will be mislead to thinking they're getting the 4.10s with the automatic.

JohnT11 09-26-2011 12:14 PM

I got the 3.21s (against my will), and I'm not disappointed in the least. Does it have the pickup of my old 400 V8 GTO? No. But when you stomp on the gas, it takes off, so I'm good.

Another way to look at a numerically lower ratio is that it's less wear and tear on your engine since you'll be at lower RPMs. It probably won't be noticeable, but you never know.

panthermark 09-26-2011 12:53 PM

Quote:

Originally Posted by MrMagoo (Post 1603691)
Very misleading window sticker. I think it would it be a reasonable conclusion to think you were getting the 4.10 if that were the only ratio listed. I wonder how many potential owners will be mislead to thinking they're getting the 4.10s with the automatic.

I agree...
That is very poor communication on Jeeps part. If I walk up and look at the window sticker...and is says 4.10's standard.....with the automatic tranny marked as optional....I would assume it has 4.10's. I know buyers need to do their homework....but a buyer should not have to go through the history of the JK to figure out which models years and options were offered as what....just to find out if the a Rubi has 4.10's or 3.73's.

subunix 04-10-2012 09:11 PM

Quote:

Originally Posted by MrMagoo (Post 1603691)
Very misleading window sticker. I think it would it be a reasonable conclusion to think you were getting the 4.10 if that were the only ratio listed. I wonder how many potential owners will be mislead to thinking they're getting the 4.10s with the automatic.

AGREED! Im currently dealing with this on my '12 Rubicon, I was told by the dealer that I had 4.10's, didn't find out until i got my build sheet that i actually have 3.73's (didn't know to check that first, first jeep) called them today (dealership) and they still swear I'm supposed to have 4.10's , something to do with me having the max tow package... ill post an update when i hear back... incredibly frustrating... anyone know if there are seperate part numbers on the rear axle for 3.73 vs 4.10? i snapped a pic of my rear axle part number if anyone has any info

jeepkingtn 04-10-2012 09:29 PM

I have 4.10's on my 2012 JKUR Automatic. Didn't cost extra, are great off-road too!

Comac90 04-10-2012 11:28 PM

Quote:

Originally Posted by jeepkingtn (Post 2243346)
I have 4.10's on my 2012 JKUR Automatic. Didn't cost extra, are great off-road too!

You may want to double check your window sticker. Assuming there has not been some mid-year pricing change that I'm unaware of, if 4.10s are not specifically listed under optional equipment as "4.10 Rear Axle Ratio" for a $50 charge, then I would question whether you actually have 4.10s.

The only exception that I know to this is on the Rubicons (autos AND manuals) that hit D1 status prior to or around 7/6/2011 ... all Rubicons that hit D1 prior to ~7/6/2011 had 4.10s. On those first few, I have no idea what the window sticker said .... anyone??? UpHillBill may chime in and be able to shed some more light - he had to go through quite a bit of work, as I recall, to get his changed from the then standard 4.10s to 3.73s.

Bottom line as has been said: for Rubicons, 4.10s are standard on the manual, 3.73s are standard on the auto and 4.10s are optional on the Rubicon auto for a $50 charge (again, assuming there hasn't been some mid-year pricing change I'm unaware of).

T

Thracks 04-11-2012 12:43 AM

Quote:

Originally Posted by JohnT11 (Post 1604388)
Another way to look at a numerically lower ratio is that it's less wear and tear on your engine since you'll be at lower RPMs.

This is false. Taller gears puts a higher load on your engine because it has a less usable range with the gears being further apart. Low gears allow your engine to work less while producing more wheel torque since the power is multiplied that much more.

alang_z33 04-11-2012 02:28 PM

Be sure your not seeing the "4:1 Rock-Trac Part-Time 4WD System" listed in the standard equipment section and confusing that with 4.10 gears. This is referring to the transfer case ratio.

Your window sticker should explicitly say "4.10 Rear Axle Ratio" under optional equipment. I had to look around for a while to find an auto with this.

Comac90 04-11-2012 03:44 PM

Quote:

Originally Posted by Thracks (Post 2244368)
This is false. Taller gears puts a higher load on your engine because it has a less usable range with the gears being further apart. Low gears allow your engine to work less while producing more wheel torque since the power is multiplied that much more.

I don't totally follow you on the 'less usable range with the gears being further apart comment.' ... what do you mean? What gears? Diff gears between 2 different rigs? Drive ratios between each gear in the tranny?

It sounds like you're saying that at a given RPM, 3.73s put higher stresses on the engine than 4.10s because the engine is operating outside of it's optimal RPM range. By that logic, 5.88s would put a lot less wear and tear on an engine than 3.21s ... which doesn't make sense to me.

Do you have some references or something to back that up? :thumb:

bkap305 04-11-2012 03:56 PM

My 6 speed standard Rubi came with 4:10 and I wouldn't have it any other way. It is quick off the line, shifts at a comfortable rpm, and gets between 18 and 21 mpg. It is a 2012.

-JC- 04-11-2012 04:00 PM

I'm not sure if this relates to what is being said, but I have a '12 Rubi JK with 4.10, manual tranny. 1st gear is almost unuseable on flat ground. IT essentially just gets the jeep moving, at 10mph I'm at 3000rpm. On flat ground, I usually start in 2nd. More than enough power.

12JKUR 04-11-2012 04:01 PM

My 12 rubi came w/4.10s at no charge. Not sure ive seem a rubi w/out. My sticker shows 4.10s.

If you don't mind 15mpg, they are the way to go, if not, order one w/3.73's

Matador 04-11-2012 04:02 PM

Quote:

Originally Posted by alang_z33 (Post 2245994)
Be sure your not seeing the "4:1 Rock-Trac Part-Time 4WD System" listed in the standard equipment section and confusing that with 4.10 gears. This is referring to the transfer case ratio.

Your window sticker should explicitly say "4.10 Rear Axle Ratio" under optional equipment. I had to look around for a while to find an auto with this.


Exactly.
Here is a copy of my window sticker

http://images5a.snapfish.com/2323232...98%3B349nu0mrj

jeepkingtn 04-11-2012 09:35 PM

My window sticker says the same thing.

Comac90 04-12-2012 06:41 AM

Quote:

Originally Posted by jeepkingtn (Post 2247657)
My window sticker says the same thing.

Out of curiosity, whats the build date? I'm thinking you have one of the first ones built since the very first 2012 rubicons with autos built DID have 4.10s at no charge. Whats gonna be odd is if its not July/2011.

T


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