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Discussion Starter · #1 ·
The local jeep dealer is just awful when it comes to selection. I am still on the fence between auto & manual. With that in mind, could i tell the difference between a 3.73 & 4.10 auto? 3.73 & 4.10 manual?

Earlier this year i was posting a ton and got super close to buying JKUR white, manual but it just felt wrong. What a great decision as my wedding was more expensive than i planned along with some other out of the blue expenses. Now i have my sites set on a 2013 JKUR billet.

I have driven a 2012 - 3.21 JK manual and a 2012 - 3.73 JKU auto. Thats it so it is hard to compare. Ive read all the comparisons of gas mileage and which to get based on your upgrade path. But i want to know if i could feel the difference driving stock.
 

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On stock tires, you probably won't notice much except when on the highway doing 70mph. But if your planning for bigger tires in the future then 4.10's will work a lot better for 35's. I was one of those who thought I would never want 35's but over time I realized that I really want them. So 4.10's make for easier mods later especially for the JKU.
 

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Just around town (below 45 mph) and in stock format...I doubt it will be a huge difference.

On the highway (in the auto), you may wish you were spinning less than 2500 RPM's at 70mph in stock format.
 

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Discussion Starter · #4 ·
i just felt that when driving the 3.21 jk the gears were "short" ... as in i had to shift a bunch of times to get up to decent speed (i currently drive WRX, which may be my problem, what i am used to).
 

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i just felt that when driving the 3.21 jk the gears were "short" ... as in i had to shift a bunch of times to get up to decent speed (i currently drive WRX, which may be my problem, what i am used to).
Well, that's the opposite of what you should feel with 3.21s. With 3.73s or 4.10s, your RPMs would climb MORE quickly relative to speed than with 3.21s.

For example, I've seen some owners of manual trans Rubis with 4.10s complain about feeling the need to shift into 2nd gear before they're even across the intersection. Some just start in 2nd gear.

Personally, I would always go with the deepest stock gearing available. That'll be 3.73s on non-Rubis or 4.10s with a Rubi.

For you though, you've got to test drive them. There is no amount of forum posts you can make that will actually impart the difference (if any) you'll feel from one to the other. Convince your dealer to bring in some more options, or go elsewhere.
 

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Discussion Starter · #6 ·
yeah thats why i said its probably the feeling of the WRX that makes it odd for me (i wasn't driving it the first time i drove the new jeeps and loved the manual).

i will have to get out and test drive more. hopefully other dealers near here have more options. i just hate the pushy salesman part that happens when you test drive vehicles (at least that has been my local experience).
 

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i just felt that when driving the 3.21 jk the gears were "short" ... as in i had to shift a bunch of times to get up to decent speed (i currently drive WRX, which may be my problem, what i am used to).
I think that has more to do with the transmission than the axle ratio.


The NSG370 in the Jeeps is the "close ratio" version. There is less difference between the gear ratios than with a wide ratio, giving you a lot more overlap within the power band of the engine. So if you wrap out first gear, you're already through a good portion of where you would want to be in 2nd. And when you wrap out 2nd, you're already through a bit of 3rd, etc.

If you swap in a wide ratio NSG370 you'd get a deeper first gear (5.01 vs 4.46), second gear would get closer (2.83 vs 2.61), third gear would be almost the same (1.79 vs 1.72) and the rest are so close you couldn't tell the difference.

But here's the thing. The wide ratio transmission would have you shifting earlier than the close ratio. You'd end up getting through the power band of the engine sooner in the lower gears, causing you to have to shift even earlier.

My last manual transmission vehicle before the JK was an 04 GTO. The V8 had a ton of torque and a first gear that was closer to the second gear in the Jeep. Your WRX is set up the same way because it too has more power (and probably less weight) than the Jeep. Both of those vehicles have a first gear that isn't nearly as deep as the Jeep. That's why they could get to a much higher speed before you needed to shift into second. The deeper the transmission gear, the faster you get to the point where you have to shift.

One other thing to notice is that in the GTO and the WRX, the 6 speed has 2 overdrives. 4th gear is 1:1 in both of those cars. In the Jeep, 5th gear is the 1:1 and 6th is the one overdrive. More steps to the 1:1 means more shifting as you get up to it.

The Jeep has a truck transmission with a deep first gear that requires you to shift sooner than a car transmission. That's just the way it works out.


Oh, and FWIW 3.21 gears are "tall" (i.e. they will let you run at a higher speed before hitting redline) where the 3.73 gears are "short" (i.e. they will cause you to hit redline at a lower speed).
 

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rics1997 is correct...on the interstate is the only place you'll "feel" the difference. With 4.10s the tach will be screaming above 70MPH. I have the 3.73s, 6-speed, and 33x12.50 tires and I feel like it's honestly perfect. I would not want the 4.10s even if you'd give them to me for free. 3.55s would actually be perfect, but since that's not offered anymore 3.73s it is.
 

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Discussion Starter · #9 ·
wow thanks for the explanation derf. i kinda knew that, but not as clearly as you described it.

i guess i just need to figure out what is more important and decide.
 

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wow thanks for the explanation derf. i kinda knew that, but not as clearly as you described it.

i guess i just need to figure out what is more important and decide.
It took me about 2 hours of driving to get used to the shifting in the Jeep after 6 years of driving the GTO.

Sure, the shifter throw is measured in miles by comparison. Sure, you have to shift sooner coming out of first and second gear. Sure it doesn't have the same punch when you hit the accelerator. But I don't regret it in the slightest.
 

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OT

derf....are you grimmjeeper? (Is that your site?) I use that site ALL THE TIME!
 

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Yep. That's me.
Fantastic site!
:thumb:
I think UHB (Up Hill Bill) linked to it about a year ago...and I've used it ever since.
 

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It's been evolving since I started the planning for my CJ project in 2004. It seems I've done more with that website than I have with my CJ which still isn't done. :(

I'm looking at finishing up some significant upgrades this winter when I'm snowed in.
 

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Discussion Starter · #15 ·
so derf, here is a question then, and i know its been beaten to death.

if you could go back, would you get auto tranny? i was so set on manual tranny (most of my driving life has been on a manual) i wouldn't hear about anything else. lately i have been entertaining the auto, because, lets be honest its a lot easier to offroad in it and majority of my time driving is spent driving around town. also, it allows my wife to drive it incase i drink too much out :) (she can get by in a stick but its painful to be in the car with her). i think i change my mind every day about which one.
 

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That's really a tough one to give advice on because each person is different and has different needs and wants. Both sides of the argument have pros and cons that have been beaten to death for generations. But really it comes down to personal preference and which pros and cons end up being more important to you. Personally, I wouldn't get an automatic. But that's because the manual is more in line with what I need and want for myself.

I don't have to share the Jeep with anyone. While that's a consideration for you, it's not for me. I'd encourage a wife to learn how to drive a stick (better) but again, that's me. It may be completely different for you. It may be worth getting the auto. I hear good things about the new auto they use in the 12/13.

My JK is not my technical rock crawling rig. If I ever get the CJ done it'll serve that duty. It has an automatic and will have a 4 speed Atlas t-case to give me all sorts of combinations of options when crawling. I was originally going to go with a different drivetrain with an SM465 manual but that ended up not working out. I went to the automatic because a) I had it in the garage, and b) it does have some benefits when rock crawling.

This JK is primarily my daily driver. I prefer to drive my car rather than just ride in it which is why I wanted a manual. Again, that's personal preference.

Given where I live right now, I don't have a lot of really challenging off road trails anywhere near me. For the trails around me, a manual should be no problem. If I do move back to Texas or Oklahoma, or if I manage to find my next job in Colorado where I really want to end up I'll have access to a lot of trails but that's a couple of years down the road.

I just bought this JK less than a month ago and I'll be popping its cherry on the trails this weekend so I'll know better how I like the manual. The picture in my avatar is a rental I had in Colorado last July. I only hit easy trails but it did great the whole trip. I'm going to try some harder trails if I can and get a better sense of how I like it.

I don't know if that helps or not but I try not to choose sides when giving advice to someone about which to choose. I gave you the list of why I chose what I chose. I'd recommend sitting down with the wife and weighing the pros and cons and how they apply to you and your situation and coming to a conclusion that will make you and the wife happy.
 

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I know in mine when shifting I typically go 1-3-5 and then 6 if necessary going to about 3K rpm before shifting. I'm sure towing the overlap will be nice.
 
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