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Old 12-09-2011, 08:36 PM   #31
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Originally Posted by i82much View Post
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.
Exactly

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Old 12-09-2011, 08:39 PM   #32
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Quote:
Originally Posted by blackforestgreen

kj what year is your jeep? At the dealer i bout my sport from, all the rubicons were 3.73.
07

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Old 12-09-2011, 08:42 PM   #33
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I gotta agree with that !


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Exactly
Even though my '08 behaves, like less that 1% of the other 07/11 Rubis !!

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Old 12-09-2011, 08:52 PM   #34
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07
hey kj, big diff between these 07 to 11, with this new trans and engine. numbers don't tell the whole story. try test driving and you will understand the difference. not saying i would run out and trade my 08 jku for this, and i don't know all the engineering math between the two, but you will find a 3.73 ratio on these new jeeps more than sufficient.
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Old 12-09-2011, 08:57 PM   #35
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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.
You too can get 20 mpg in your 2012 Rubi..well on the highway at least... all you have to do is drive 55 mph. At 60 you should be getting 18 mpg/highway
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Old 12-09-2011, 09:11 PM   #36
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Originally Posted by blackforestgreen

hey kj, big diff between these 07 to 11, with this new trans and engine. numbers don't tell the whole story. try test driving and you will understand the difference. not saying i would run out and trade my 08 jku for this, and i don't know all the engineering math between the two, but you will find a 3.73 ratio on these new jeeps more than sufficient.
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Old 12-09-2011, 09:44 PM   #37
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In my opinion it has as much to do with the driver as the tires and gearing. On our 2011 GC Hemi my wife has never seen 17.5 mpg on a tank of gas I get 19.5 consistantly. Same vehicle same 80% highway/20% city only diference is who's behind the wheel and most of it is directly linked to how we leave a stoplight or stop sign.
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Old 12-09-2011, 09:48 PM   #38
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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.
I've looked thru all the posts thru #36, and this one says it best. I test drove a 2012 Rubi 4.10 Auto a couple days ago. I can only describe it as a 'hot rod'. I am absoutely sure that we didn't come close to even 10mpg during our 'quick' test drive tho. The test drive was just to see what the 4.10 Auto-equipped Pentastic felt like.

We traded our 2011 Rubi 4.10 auto (CAI, Performance catback exhaust) for a 2012 Arctic Edition (basically a Sahara with a few suspension upgrades), 3.21 Auto. We've only had it a couple days, but seat of the pants impression is the reason we got it. We can pull out and pass vehicles that we would have just stayed behind. And we have!

I realize the original question was 3.73 vs 4.10, but I'm saying a 3.21 with the new engine will make you quite happy, and will PROBABLY provide the best MPG of the bunch. I've learned previously that you CAN overgear, causing the engine to lug and mileage to suffer; but a 2012 JK is NOT overgeared for road use with 3.21.

We are planning on moderate off-roading, so the 3.21 in low range will still be quite adequate.

This is all 2-door oriented, but if you have 4-door then I would stay with 3.73 or lower (numerically higher). Our 2-doors also have the stock tire height of about 32".
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Old 12-09-2011, 10:07 PM   #39
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Originally Posted by blackforestgreen View Post
KJ what year is your jeep? at the dealer i bout my sport from, all the rubicons were 3.73.
This may indicate a trend, at least in your local area, toward higher gears. Were they 2dr or 4dr, or a mix? And they were all 2012s? Another thing to be aware of is that standard features are listed on the left of the window sticker. I don't have a window sticker in front of me, but the standard may be 3.73 for all. Look on the right side of the sticker for the Rubi option and see if an optional ratio is listed there. You may find that they are all 4.10. Or not.

A used (2011 or prior) Rubi sitting on a lot right now better have 4.10 gears, or it may be sitting there quite awhile. If a lot of Pentastar Rubis are ordered with 3.73 and offroaders come to love that ratio, then future used Rubis may do quite well with the 3.73, and 4.10 will be sought out only by serious offroaders.
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Old 12-09-2011, 10:11 PM   #40
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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.
Totally. I've got a 4.10 auto rubi and avg. about 19.5 into town, around town, fire roads, up the mountain to the ski area, etc. See posts about smooth shifting transitions in the 4.10 auto, etc.
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Old 12-09-2011, 10:46 PM   #41
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I realize the original question was 3.73 vs 4.10, but I'm saying a 3.21 with the new engine will make you quite happy, and will PROBABLY provide the best MPG of the bunch. I've learned previously that you CAN overgear, causing the engine to lug and mileage to suffer; but a 2012 JK is NOT overgeared for road use with 3.21.
Hmm. By overgear do you mean gears that are numerically too low? If so, I have always heard that referred to as "undergeared." So a jeep with 3.21's and 37's "needs more gear" or is "undergeared." I am not sure if I am being nitpicky or if I am just missing something??
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Old 12-09-2011, 11:00 PM   #42
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I had a similar question when I got my Rubi, called my friend who worked as a drivetrain engineer at jeep. He said, if you are not going to get the 4.10 then why are you getting the Rubi? Get Sahara
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Old 12-09-2011, 11:06 PM   #43
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5 speed auto RPM's at 70 mph for various configurations.
3.21 3.73 4.10
32" 1958 2275 2500
35' 1790 2079 2286

Some observations:
1. Torque curve relatively flat above 1800
2. Engine noticeably louder at 2500 vs 1950 RPM
3. Don't have hard data on MPG
4. Shifter can be used to limit transmission to 4th gear if necessary
5. Gearing doesn't matter as much between 10 mph and 55 mph since automatic will select the gear to manage the RPM's.

I have a 3.21 auto with 32" tires. I am very happy with the performance, but if I had to do it over again I would get the 3.73 to provide the flexibility to go to 35" tires. Based upon the above numbers and my experience, I believe 3.73 gears provide the best overall experience for a DD on the highway and medium duty off-roading.
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Old 12-09-2011, 11:18 PM   #44
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Rubi's are off road and off road is 4.1 it is that simple. In technically difficult situations you will want to be crawling in 4 low. If it is not being used off road then why pay the extra for the Rubi when a Sahara will do? If you go Rubi why would you kill your resale value by putting 3.73 on it? It makes no sense to me. Anybody purchasing a Rubi will be expecting 4.1 in it. It is one of the main features that is looked for in a Rubicon.
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Old 12-09-2011, 11:29 PM   #45
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Rubi's are off road and off road is 4.1 it is that simple. In technically difficult situations you will want to be crawling in 4 low. If it is not being used off road then why pay the extra for the Rubi when a Sahara will do? If you go Rubi why would you kill your resale value by putting 3.73 on it? It makes no sense to me. Anybody purchasing a Rubi will be expecting 4.1 in it. It is one of the main features that is looked for in a Rubicon.
Ok, so assume the highest gear ratio in the trans was 3:1 instead of .83 or whatever. You'd still want 4.10's??? You'd have a final drive ratio of over 12:1. The point is to have sufficient overall gear reduction for the particular situation you are in. You can juggle transmission ratios, axle ratios, transfer case ratios, and tire sizes to achieve the appropriate gear reduction for your application.
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Old 12-09-2011, 11:44 PM   #46
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You guys make me smile . Try getting into a 3 speed auto with 3.07's and 32" tires getting at best 12mpg. Running 2200rpm at 55mph. Come complain when you got something to complain. Just be happy
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Old 12-09-2011, 11:53 PM   #47
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Ok, so assume the highest gear ratio in the trans was 3:1 instead of .83 or whatever. You'd still want 4.10's??? You'd have a final drive ratio of over 12:1. The point is to have sufficient overall gear reduction for the particular situation you are in. You can juggle transmission ratios, axle ratios, transfer case ratios, and tire sizes to achieve the appropriate gear reduction for your application.
The Rubicon is the most off road capable jeep in the lineup. The 4.1 gears are especially important in 1st gear for crawling in low and for me, towing in high in addition to the crawling. When you purchase a Rubicon, either new or used most jeepers are expecting the low gearing. It is one of the signature parts of it. So what I'm saying is that if you are buying it for road use and economics, get the Sahara with 3.73. This is primarily aimed at the OP who is trying to decide 3.73 vs 4.1.
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Old 12-09-2011, 11:56 PM   #48
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Originally Posted by theotis View Post
5 speed auto RPM's at 70 mph for various configurations.
3.21 3.73 4.10
32" 1958 2275 2500
35' 1790 2079 2286

Some observations:
1. Torque curve relatively flat above 1800
2. Engine noticeably louder at 2500 vs 1950 RPM
3. Don't have hard data on MPG
4. Shifter can be used to limit transmission to 4th gear if necessary
5. Gearing doesn't matter as much between 10 mph and 55 mph since automatic will select the gear to manage the RPM's.

I have a 3.21 auto with 32" tires. I am very happy with the performance, but if I had to do it over again I would get the 3.73 to provide the flexibility to go to 35" tires. Based upon the above numbers and my experience, I believe 3.73 gears provide the best overall experience for a DD on the highway and medium duty off-roading.
This was one of the hardest choices for me. It is only $50 (and might be free now)...but choosing between 3.21's and 3.73's is a big decision because it is very expensive to do over at a later date.

The ability to shift down at anytime....and the fact that in all honesty I'll do very little off-roading is why I'm leaning towards 3.21's. I would really like 3.55's. My Libby has the 42RLE with 3.73's (but 29 inch wheels) and I've never had the desire to go with bigger wheels or do serious off-roading.
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Old 12-10-2011, 12:01 AM   #49
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Because there are two different auto tranny's with gear ratio's that are nothing alike...talking strictly axle ratio is pretty inaccurate. Final drive ratio would be much more precise.

4.10's in the 42RLE are a lot different than 4.10's in the W5A580.
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Old 12-10-2011, 12:07 AM   #50
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4.1 is looked at mostly on the low end for crawling and towing. That is one of the main concerns when off road....the purpose of a Rubicon.
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Old 12-10-2011, 12:10 AM   #51
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The Rubicon is the most off road capable jeep in the lineup. The 4.1 gears are especially important in 1st gear for crawling in low and for me, towing in high in addition to the crawling. When you purchase a Rubicon, either new or used most jeepers are expecting the low gearing. It is one of the signature parts of it. So what I'm saying is that if you are buying it for road use and economics, get the Sahara with 3.73. This is primarily aimed at the OP who is trying to decide 3.73 vs 4.1.
Well, sure but ... people are expecting the 4.10 because they've been building Rubi's that way with the 4 speed trans for so long ...

and as I mentioned earlier, if it is economics you are after, the rolling resistance and extra weight on those KM's is probably going to cost you more mpg than the 4.10's.
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Old 12-10-2011, 12:19 AM   #52
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Well, sure but ... people are expecting the 4.10 because they've been building Rubi's that way with the 4 speed trans for so long ...

and as I mentioned earlier, if it is economics you are after, the rolling resistance and extra weight on those KM's is probably going to cost you more mpg than the 4.10's.
In the MT there is not much difference. In the AT certainly in the 2012 it is different. Crawling is crawling though and that is what the lower gearing is primarily selected for. Over technical terrain you want to crawl and low gearing is what does that. A secondary benefit to the lower gearing is better torque delivered to the wheels in 1st gear...very important when towing. In the six speed manual, I never am in 6th gear while towing near the limit of 3500 lbs. That would be the same with 3.73 gears. I've towed my trailer with both. I would want the 4.1 in that situation hands down.

Economy is a whole different beast. For that, we are usually talking for on road use and I would recommend 3.21 for that. Not as responsive but yes, it is more economical. Those are the two extremes for stock jeep.
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Old 12-10-2011, 12:24 AM   #53
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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?
I have the 4.10. It does just fine at all speeds. You might lose 1mpg (max) over the 3.73, but it makes the Jeep feel like a sports car -- hit the gas, and it goes HOOOOOowwwwwl and takes off like a rocket! Given that Jeeps aren't exactly fuel-efficient in the first place, and given how *fun* it makes the Rubicon, I'd tell the dealer, "gosh, y'know, I really didn't want the 4.10, but if it's a big deal to change it out and it's free I guess I'll take it..."
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Old 12-10-2011, 12:28 AM   #54
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I have the 4.10. It does just fine at all speeds. You might lose 1mpg (max) over the 3.73, but it makes the Jeep feel like a sports car -- hit the gas, and it goes HOOOOOowwwwwl and takes off like a rocket! Given that Jeeps aren't exactly fuel-efficient in the first place, and given how *fun* it makes the Rubicon, I'd tell the dealer, "gosh, y'know, I really didn't want the 4.10, but if it's a big deal to change it out and it's free I guess I'll take it..."
And this is what I mean when I say extra torque at the wheels. I didn't need the new jesus engine to determine that because we have had the jesus transmission since the JK started and that includes my 08. My engine is not that much different than the jesus model but it sure is zippy with 4.1 and the 6 gear jesus transmission.
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Old 12-10-2011, 12:32 AM   #55
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In the MT there is not much difference. In the AT certainly in the 2012 it is different. Crawling is crawling though and that is what the lower gearing is primarily selected for. Over technical terrain you want to crawl and low gearing is what does that. A secondary benefit to the lower gearing is better torque delivered to the wheels in 1st gear...very important when towing. In the six speed manual, I never am in 6th gear while towing near the limit of 3500 lbs. That would be the same with 3.73 gears. I've towed my trailer with both. I would want the 4.1 in that situation hands down.

Economy is a whole different beast. For that, we are usually talking for on road use and I would recommend 3.21 for that. Not as responsive but yes, it is more economical. Those are the two extremes for stock jeep.
I don't think we're really disagreeing about anything from a technical perspective. I don't see why the OP would want the 4.10's though, he did order an auto and indicated it would see mostly highway usage. For my part, if I were looking for a '12 Rubi auto I would probably be indifferent to the 4.10 vs. 3.73. One is a little more snappy, the other may get a bit better mpg and less engine wear. In either case the gearing should be fine with 33's on the highway and offroad, especially with the rubi tx case.

To the OP - I guess you've figured out that we're really splitting hairs here. You really can't go wrong either way
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Old 12-10-2011, 12:35 AM   #56
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4.1 is looked at mostly on the low end for crawling and towing. That is one of the main concerns when off road....the purpose of a Rubicon.
I agree 100%....
But I think that splits off into all most two separate topics.
1. If people are not crawling...why are they buy Rubi's with 4.10's...especially in the 2012's? IMO, a big part of the reason for buying a Rubi is for the gearing AND the Dana 44 up front...so that you can add 35's and wheel without gussetts and sleeves. And no matter what, all Wranglers have limited towing abilty.

2. Are people more focused on the "4.10" aspect of a Rubi than on the actual production?
In 1st gear in 4L, the drive ratio for the 42RLE with 4.10's is 46.58 (on stock wheels).
In 1st gear in 4L, the drive ratio for the W5A580 is 58.88 (on stock wheels).

Just for comparison, 3.73's on a Rubi on the W5A580 would be 53.56. 4.88's on a Rubi with the 42RLE would be 55.44.
4.56's on a Rubi with the 42RLE would be 51.80.

As far as the OP is concerned...based on his usage...a 2012 auto Rubi with 4.10's is the last thing he needs.
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Old 12-10-2011, 12:36 AM   #57
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I don't think we're really disagreeing about anything from a technical perspective. I don't see why the OP would want the 4.10's though, he did order an auto and indicated it would see mostly highway usage. For my part, if I were looking for a '12 Rubi auto I would probably be indifferent to the 4.10 vs. 3.73. One is a little more snappy, the other may get a bit better mpg and less engine wear. In either case the gearing should be fine with 33's on the highway and offroad, especially with the rubi tx case.

To the OP - I guess you've figured out that we're really splitting hairs here. You really can't go wrong either way
I think that is a fair statement. The previous two posts about torque is important to some of us. Just because we buy a jeep doesn't mean we don't appreciate an extra little bit of snappy when you put the pedal to the metal.
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Old 12-10-2011, 12:42 AM   #58
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I agree 100%....
But I think that splits off into all most two separate topics.
1. If people are not crawling...why are they buy Rubi's with 4.10's...especially in the 2012's? IMO, a big part of the reason for buying a Rubi is for the gearing AND the Dana 44 up front...so that you can add 35's and wheel without gussetts and sleeves. And no matter what, all Wranglers have limited towing abilty.

2. Are people more focused on the "4.10" aspect of a Rubi than on the actual production?
In 1st gear in 4L, the drive ratio for the 42RLE with 4.10's is 46.58 (on stock wheels).
In 1st gear in 4L, the drive ratio for the W5A580 is 58.88 (on stock wheels).

Just for comparison, 3.73's on a Rubi on the W5A580 would be 53.56. 4.88's on a Rubi with the 42RLE would be 55.44.
4.56's on a Rubi with the 42RLE would be 51.80.

As far as the OP is concerned...based on his usage...a 2012 auto Rubi with 4.10's is the last thing he needs.
If you are saying that he should back out of the deal and change to Sahara with 3.73 I would agree. But as to the question of letting the sale go through with 4.1 as apposed to 3.73 I would say that the difference isn't significant enough to back out. The benefit is a more snappy jeep while passing. It will be noticeable in either the standard or automatic.
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Old 12-10-2011, 12:43 AM   #59
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I know! If you get the 4.10's and you need to keep your RPM's down for freeway use, well, duh ... just put bigger tires on it!!!
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Old 12-10-2011, 12:43 AM   #60
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Quote:
Originally Posted by panthermark View Post
I agree 100%....
1. If people are not crawling...why are they buy Rubi's with 4.10's...especially in the 2012's?
Even in a street Rubi, it makes it *fun* because it makes it scoot like a scalded rabbit. And isn't fun the whole point of a Jeep Wrangler?

Yes, it''ll cost you 1mpg on your highway gas mileage, so you'll get 20mpg rather than 21mpg (or 19mpg rather than 20mpg if running at 70 rather than 60), big deal, if you want mpg buy a Hyundai. Yes, the engine will run at a higher RPM on the highway. No, it's not a big deal. The Pentastar is smooooooooooth. You can run it at 2800 rpm and 75 mph all day long and the only expression it'll put on your face is a grin, not a grimace. Not like the rough old minivan engine at all, which always thrashed once you started getting up in the RPM's...

In other words, I have the 4.10 in my auto Rubi and find no downsides at all given that I was looking for *fun* -- and it gives me that in spades, whether on-road or off .

(Note: I have owned my Rubi for 2 months now and have 3800 miles on it. Around 2000 of those are high speed highway miles getting to and from wheeling sites in the northern Mojave Desert. No problem!)

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