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Topic Review (Newest First)
06-24-2012 01:49 AM
MarineHawk
Quote:
Originally Posted by MTH View Post
Have you ever driven a 3.6 auto on 35s with 4.56s?
FWIW, I think my comments above account for that question. But I have not driven a 3.6L with 4.56 gears. I have, however, driven a 3.6L with 3.73 gears in 4th-gear, which is equivalent to driving my Jeep with “4.49” gears (pretty close to 4.56 gears) in 5th gear. And guess what? I don’t like it 95% of the time. And neither does my transmission, which stays in 5th at 2,100 rpm at 70 mph on non-steep terrain. I would not want to regear so that my top gear works like my 4th gear now, which is what I would have if I regeared to 4.56s. I know that from pulling my shifter to the 4.56 (4th-gear) option and over-reving on normal highway conditions. My transmission agrees and doesn’t do that unless I sadly make it do so.

And one of the important factors that makes the oft-cited silly gear charts impractical is that they lump Rubis in with Saharas and Sports when purportedly telling Jeep owners what gearing is appropriate for “rock crawling and higher elevations.” If these charts really could have any relevance, there would have to be different ones for 4.0:1 t-cases (Rubis) and 2.72:1 t-cases (Saharas and Sports). That’s a full 47% difference in gearing when doing “rock crawling a[t] higher elevations.” And the chart doesn’t even try to account for that.

In low-range, my Rubi with 3.73 gears is geared the same as a Sport or Sahara with “5.49” gears. So, my Jeep is geared in low-range lower than a Sport or Sahara with the same tires is geared with 5.38 gears. Thus the all-mighty charts sloppily lump vehicles with vastly-different t-cases together in determining which ones are geared properly to perform “rock crawling a[t] higher elevations.” "Rock crawling" is done in low-range. Period. Bunk.

Quote:
Originally Posted by MTH View Post
Have you ever driven a 3.6 auto on 35s with 4.56s?
Have you driven any 3.6L? A 2012 Rubi rock crawling with 3.73 or 4.10 gears? Why the advice that this is not ideal? Incomplete and misleading paper charts? Drive before you advise?
06-23-2012 11:01 PM
MarineHawk
Quote:
Originally Posted by MTH View Post
... What percentage of peak power are you using at 2100 RPMs with 3.73s turning 35s? ...
You don't want peak power when you're just cruising comfortably and efficiently down the highway, in which case you're not doing a NASCAR race. You get peak power when you want to pass or climb Floyd Hill at speed by punching the gas and the trans downshifts "automatically" to the gear that gives you peak power and more rpm. You're just burning extra gas and wearing the engine out by operating at "peak" power when you don't need it. Peak power is called "peak" power for a reason. It's not for when you're trying to be efficient and just cruising down a level highway. The vehicle knows when the gearing is too low and downshifts. That's what overdrive is, and has been for decades, all about: avoiding peak power when it's unneccessary and unhelpful.

And in that context, my transmission seems to know what it's doing. It seems to like 2,100 rpm and sticks pretty close to it under most speeds and most gears unless I punch it. So my auto trans keeps me around 2,100 rpm in other conditions. It couldn't do it if I regeared to too low of gearing in which case it would over-rev at the top end. No reason for that.

At 35 mph, my trans keeps me also at 2,100 rpm. It's doing the right thing. It knows that reving up to 2,700 rpm is dumb when you don't need it.
06-23-2012 06:24 PM
MTH
Quote:
Originally Posted by MarineHawk
You really oughta drive one.

Mine with my exact tires appears (according to my odometer) to put out about 2,100 rpm at 70 mph, which is pretty close to what the chart says. It's pretty great on level highways or those with moderate hills. That's what transmissions are for. When I go up a steeper hill or want to accellerate, it goes into 4th gear, which is doing about 2,530 rpm at 70 mph. I don't want to lower my top gear, which works perfectly for at least 95% of my highway driving, when I can downshift for the other 5%.

2,530 is more than enough rpm with the 3.6L (you really should consider stopping looking at paper and actually drive one). For example, even a pre-'12 with 5.38s and 35s is only doing 2,495 rmps at 70 mph (see 3.8L chart). To get to 2,700 rmp in 4th-gear with a 3.8L auto at 70 mph, you have to put 5.86s in it. Who does that? Too low.

You definitely don't need to (and I would never want to) idle down the highway at 2,700 rpm at 70 mph with the 3.6L. At 77 mph, you would be reving at 3,000 rpm. Too high, but if you want to do that, just downshift.
Have you ever driven a 3.6 auto on 35s with 4.56s?

What percentage of peak power are you using at 2100 RPMs with 3.73s turning 35s? I'm sure it's enough, but it's not going to be ideal IMO. That you're able to move comfortably along doesn't mean you're actually using the engine optimally.

These small V6s aren't V8s or diesels--they do well with RPMs.
06-23-2012 05:58 PM
MarineHawk You really oughta drive one.

Quote:
Originally Posted by MTH View Post
... don't 3.73s put a 2012 auto around 1900 RPMs on 35s at 70 mph? ... I'd want to be at about 2700 RPMs on the highway. ...
Mine with my exact tires appears (according to my odometer) to put out about 2,100 rpm at 70 mph, which is pretty close to what the chart says. It's pretty great on level highways or those with moderate hills. That's what transmissions are for. When I go up a steeper hill or want to accellerate, it goes into 4th gear, which is doing about 2,530 rpm at 70 mph. I don't want to lower my top gear, which works perfectly for at least 95% of my highway driving, when I can downshift for the other 5%.

2,530 is more than enough rpm with the 3.6L (you really should consider stopping looking at paper and actually drive one). For example, even a pre-'12 with 5.38s and 35s is only doing 2,495 rmps at 70 mph (see 3.8L chart). To get to 2,700 rmp in 4th-gear with a 3.8L auto at 70 mph, you have to put 5.86s in it. Who does that? Too low.

You definitely don't need to (and I would never want to) idle down the highway at 2,700 rpm at 70 mph with the 3.6L. At 77 mph, you would be reving at 3,000 rpm. Too high, but if you want to do that, just downshift.
06-23-2012 05:23 PM
MTH
Quote:
Originally Posted by MarineHawk

Thus, with a 2012 auto with 4.10s, you're driving something geared a little lower than a 2011 with 4.88s, even if you don't believe the new engine makes any difference.
And I don't think that's low enough. If I ended up with a pre-2012 auto, I'd want 5.13s with stock tires. 5.38s as soon as I crested into 33s+.

The 3.6 has a higher redline than the 3.8. And IIRC (I don't have my charts and I'm not going to bother with the math . . .) don't 3.73s put a 2012 auto around 1900 RPMs on 35s at 70 mph? Have you looked at the dyno print out? That's leaving a ton of power on the table.

I'm sure it works fine. But that's different than "ideal."

I'd want to be at about 2700 RPMs on the highway. That looks to be about right for both engines IMO. Whatever gearing puts you there, is the right one. JMHO.
06-23-2012 03:41 PM
MarineHawk It seems like most, if not all, people saying that 3.73s or 4.10 are anything but ideal for 35s are ... the people who don't drive that combination. I have 3.73s and 35s, and I can say with absolute certainty that I definitely would never want anything more than 10% lower gearing (4.10s) than what I have now. 4.56s much less 4.88s would be way too low for me with my setup. People I think keep forgetting that the gearing of the 2012 auto also is different than the pre-'12 autos, and the 3.6L does make a difference even at moderate revs. Actual experience here of about 1,000 miles per month.

The 1st-gear auto ratio for a 2011 Wrangler is 2.84:1.

The 1st-gear auto ratio for a 2012 Wrangler is 3.39:1.

That's 19.4% lower gears in 1st gear for the 2012s.

That means a 2012 auto with 3.73s in first gear (even aside from the different engine) is like a 2011 auto with 4.45:1 gears (almost like 4.56s) in first gear.

And a 2012 auto with 4.10s in first gear (even aside from the different engine) is like a 2011 auto with 4.89:1 gears (basically 4.88s).

If any chart suggests otherwise, it is not credible. I may have missed it somewhere, but I have yet to hear of anyone with 4.10s, 35s, and a 2012 auto who thinks their gearing is too high. Only people who probably have never driven that combination say that.

Also, interestingly, even the 5th-gear in the 2012 auto (0.83:1) is lower than the 4th (top) gear in the 2011 (0.69:1). That’s 20.3% lower top gearing in the 2012. Thus, even in the top gear in the 2012, you have even lower gearing relative the to pre-‘12s than in 1st gear.

Thus, with a 2012 auto with 4.10s, you're driving something geared a little lower than a 2011 with 4.88s, even if you don't believe the new engine makes any difference. And you have 25% more gears. And you have a different engine.
06-23-2012 02:11 PM
Creepin__Jeeper Hey guys thanks for the input I really appreciate it, unfortunately that particular Jeep didn't work out but I've made some changes to my option list and it seems like there is one lined up. I should be able to take deliver on Monday as long as the dealer transfer goes through.

This new one has some extras that weren't on my need list but it still fit in my price

Wanted an auto but there were none available outfitted the way I wanted or if they were they couldn't exchange them... so I decided to go with a manual so this is the details on it below:

Black JKU
24S w/ power group - needed
connectivity group - needed
3.73's - needed (this one has the max tow so it was a bonus)
Hardtop - needed (this one has the dual top so it was a bonus)
Trak-lok - Bonus
Upgraded audio package - Bonus

If I can buy this one the numbers seem really good,
I'm buying it with employee pricing event so that's a good chunk of money right off the top I'm also applying $2K from my trade and I did some hard negotiations and came out somewhere around $28,500 on the road

Maybe some of you can give some input with that info and let me know. Hopefully I can finalize everything on Monday and join this forum with some real Jeep talk.

-Robert
06-22-2012 06:38 PM
rics1997 lol
06-22-2012 06:33 PM
Up Hill Bill
Quote:
Originally Posted by rics1997 View Post
.... Under this logic then we shouldn't question the President of the US either. He obviously knows more about whats going on so his opinion should be more important then us mere mortals, right?
Yeah, point taken..... but Dave is not a know nothing, never produced anything, arrogant moron, so it's not a perfect example ...
06-22-2012 06:15 PM
rics1997 I like the trak-lok option but wouldn't call it a deal breaker. There are better upgrades in the future if you want or feel you need it. Detroit truetrac can be added at any time and many claim it is better then stock anyways because it is gear operated instead of clutch which can wear out over time.
06-22-2012 05:54 PM
rics1997 What makes Dave's opinion more then anyone else's? Just because he owns a company that mods Jeeps doesn't make him any more or less qualified on how something feels as idea. Just means he has an opinion just like everyone else and he is just as mortal as the rest of us. CEO's know business and how to run a company, it doesn't make them experts in what the company even does. Under this logic then we shouldn't question the President of the US either. He obviously knows more about whats going on so his opinion should be more important then us mere mortals, right?
06-22-2012 05:39 PM
MTH
Quote:
Originally Posted by Up Hill Bill

Yeah, MTH, but I submit to you that, when Dave Harriton, founder and CEO of AEV, writes that he has personally driven a 2012 auto with 4.10s and 35" tires, and that the gearing is "ideal" for 35"s, it should probably be given more weight than the opinion of we mere mortals.... Just sayin', as they say.....
I know. But I disagree, and don't believe that subsequently produced dyno charts don't support his opinion. Just my two cents.
06-22-2012 05:25 PM
Up Hill Bill
Quote:
Originally Posted by MTH View Post
Yeah . . . I ain't buying that.
Yeah, MTH, but I submit to you that, when Dave Harriton, founder and CEO of AEV, writes that he has personally driven a 2012 auto with 4.10s and 35" tires, and that the gearing is "ideal" for 35"s, it should probably be given more weight than the opinion of we mere mortals.... Just sayin', as they say.....
06-22-2012 04:51 PM
MTH
Quote:
Originally Posted by NFRs2000NYC View Post
According to AEV, 4.10s are ideal for 35s on a 2012.
Yeah . . . I ain't buying that.

I think there's a difference between "works just fine" and "ideal," and with all due respect to AEV I think they blurred the line there.

A look at the dyno curve of the 3.6 would suggest that you'd do better off with 35s and deeper gears. And indeed, the folks on this forum that have regeared their 2012s to 4.56 or 4.88 for 35s seem very pleased.

I think folks claiming that 4.10s are "ideal" for 35s with the 3.6 are just so used to the 3.8 needing crazy deep gears just to run reasonably well with 35s are just so pleased to not need to do that that they're calling it "ideal."

JMHO.
06-22-2012 04:10 PM
NFRs2000NYC
Quote:
Originally Posted by Daniel_M View Post
ESP, the OP is looking at a 2012. The 3.6L will turn bigger tires much easier. 5.13's would be over geared IMO for a 2012. To run 35's on a 2012 auto I think the preferred gearing is 4.56 or 4.88

-Dan
According to AEV, 4.10s are ideal for 35s on a 2012.
06-22-2012 02:47 PM
Daniel_M
Quote:
Originally Posted by ESP View Post
Your going to feel those 33s with the auto even with 3.73. If you had 4.10s and the same tranny you'd be in better shape. If you're going bigger and get a set of 35s then your power is going to noticeably drop with out 4.88s or better i.e. 5.13s. With the auto and your current gears I would stay with 33s if you want to keep as much eco and usable power right now.

A manual tranny with your gears and either 33s or 35s would be better as you could control the shift poitns.
ESP, the OP is looking at a 2012. The 3.6L will turn bigger tires much easier. 5.13's would be over geared IMO for a 2012. To run 35's on a 2012 auto I think the preferred gearing is 4.56 or 4.88

-Dan
06-22-2012 01:33 PM
NFRs2000NYC You wont feel any difference with 33s as stocks are 32s. I have 3.21s and didn't feel any difference nor MPG drop. You will be even better off with 3.73s. 35s you might feel a SLIGHLT difference with 3.73s but nothing major. Trak lock I was talked out of due to the clutches inside that is just another part to maintain/break. You would be better served getting lockers down the road.
06-22-2012 01:32 PM
MTH It's fine man, go ahead.

The most important part of jeep ownership is actually getting the jeep. Everything else in terms of features and the like you can change aftermarket if you're so inclined.
06-22-2012 01:29 PM
firehawk
3.73

hi, should be ok with the 3.73 however your mpg's will be going-
going down as your tire size go's up-up.
06-22-2012 01:28 PM
hbgirl
Quote:
Originally Posted by ESP View Post
Your going to feel those 33s with the auto even with 3.73. If you had 4.10s and the same tranny you'd be in better shape. If you're going bigger and get a set of 35s then your power is going to noticeably drop with out 4.88s or better i.e. 5.13s. With the auto and your current gears I would stay with 33s if you want to keep as much eco and usable power right now.

A manual tranny with your gears and either 33s or 35s would be better as you could control the shift poitns.
Weird; I haven't felt a difference at all. But I was told wrong then about going up to 35's Guess I'll be sticking with my lil 33's and LK ...
06-22-2012 01:17 PM
ESP Your going to feel those 33s with the auto even with 3.73. If you had 4.10s and the same tranny you'd be in better shape. If you're going bigger and get a set of 35s then your power is going to noticeably drop with out 4.88s or better i.e. 5.13s. With the auto and your current gears I would stay with 33s if you want to keep as much eco and usable power right now.

A manual tranny with your gears and either 33s or 35s would be better as you could control the shift poitns.
06-22-2012 01:13 PM
hbgirl Personal choice, really.

That's the model I went with (except no hardtop) and I've put 33's and a leveling kit on it, but I know I can go up to 35's and a real lift if (when, says the hubby) I want to with no issues, gear-wise.
06-22-2012 12:52 PM
Creepin__Jeeper
opinion on this new jeep im buying

Hey im new here and I wanted to post a thread with some questions about how this new JKU is equipped

Its a 2012 sport s with the pentastar and auto, hardtop, most important is I need input on the gears. The one I've found has the max tow which gives the 3.73's the only issue is is does not have the trak-lok option I plan on going with a lift and atleast 33's or maybe up to 35's does this seem like a good model to go with.

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