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Topic Review (Newest First)
04-29-2011 10:50 PM
rics1997 I am thinking about 305/70/17 which are 33.8 when I need new ones
04-29-2011 10:14 PM
MTH
Quote:
Originally Posted by JPWheelin
Just my $.02, but after reading through everything I would go with the 4.56s and 34 inch tire. From one OCD patient to another...I think that's the best decision given the options. .
I agree, but I originally only wanted a 33" tire. I'll probably end up at 34s only because it's so much trouble to get 4.10s. The tail is wagging the dog.
04-29-2011 09:37 PM
JPWheelin Just my $.02, but after reading through everything I would go with the 4.56s and 34 inch tire. From one OCD patient to another...I think that's the best decision given the options. .
04-29-2011 05:16 PM
MTH ^^See, I'm with you. That makes sense, even more so with the comments about your Yukons.

The tough part is how to test our theory.

Not finding much here, I posted similar threads over at JK-F, and found the group similarly stumped.

Quite simply, very few folks ever consider regearing to 4.10. I found one on JK-F who regeared his 2007 Sahara with 2007 gears--but that doesn't resolve the issue one way or the other for me.

Absent any assurances from somebody who's already done it, my only choice would be to buy the parts and pay a shop to do an install they already told me won't work. If they're right, I'm out money for parts and a failed install.

I think my solution is going to be to go with 4.56s and switch over to AT (rather than MT) tires. I can get a set of DuraTracs in a nifty 34" size (315/70/17) that are only 12 lbs heavier than my 32" BFGs. It's more tire than I wanted, but the RPMs at 70 will be a manageable 2650.

That's the plan for now anyway. It turns out that Superior--one of the very few gear companies that make 4.56s--is backordered until June. So the whole thing is on hold for the moment.
04-29-2011 04:57 PM
rics1997 on the 2007 4.10's, I got to thinking about this. They may still work and heres why I think they will

The rear Dana 44. When buying my new gears the 4.88 Yukon said they would replace all gears from 2007-2011 up and down. Since it will replace all stock gears that means the carrier must be the same in all the D44 axles which should mean the 4.10 will fit. This is non-rubi dana 44 axles.

Now the D30 is a whole different animal. For the most part the 4.10 would not fit unless you replaced the carrier. But since you plan of replacing the open diff in your front axle with a limit slip, you are in fact changing the carrier anyways. All you would need is one that fit the 4.10 gears and not the 3.21.

At least the logic says it will work
04-27-2011 02:08 PM
MTH Let me follow up here a bit with another idea: Has anybody actually installed OEM 2007 non-Rubi 4.10s in a non-2007 non-Rubi?

As I mentioned previously, I think 4.10s would be best for me to run 33s with a 6 speed. However, the shop I'm speaking with believes non-Rubicon 2007 OEM 4.10s would not fit my 2010. Something about how the OEM "install manual" recommends a different install kit for replacing 2007 R&Ps versus 2010 R&Ps. To them, this indicates some incremental year-to-year change(s) that would likely preclude success.

Of course, the shop could be wrong.

Does anybody have a different experience or know of somebody who has? Or, alternatively, have you been told the same thing?
04-26-2011 07:55 PM
rics1997 He shouldn't have to change his carrier in the d40 axle in the rear but would in the front, but since he is also getting LSD put in the d30 axle that will cover the carrier. When I was getting mine, the 4.88 gears for the d40 said it worked for all gear replacement up and down.
04-26-2011 07:32 PM
WranglerLou 4.56 or the 4.88 would be fine.. Also if im not mistaken you will need to change your carrier as well.
04-26-2011 05:37 PM
deathphoenix99
Quote:
Originally Posted by MTH View Post
I want to say 2.72:1. Rubicon JKs have the 4:1.

Thanks for all of your input.
Alright, I was just wondering how much your final drive would be with the low range.
04-26-2011 04:21 PM
JIMBOX Heh Heh, I kinda figured you'd notice that post-


Quote:
Originally Posted by MTH View Post
Which just so happens to be Jimbox's plan for his NON-DAILY DRIVER!
I'm afraid my jeep will be a DD, for at least a week while I rack up 500 miles in 20/m segments-

JIMBO
04-26-2011 04:17 PM
MTH
Quote:
Originally Posted by MTH View Post
You got that right.

To put you in a similar spot on the RPM band for your 33s as my guys are recommending for me on 33s, you'd need somewhere around 5.38s.
Quote:
Originally Posted by JIMBOX View Post
-----BINGO---

JIMBO
Which just so happens to be Jimbox's plan for his NON-DAILY DRIVER!
04-26-2011 04:11 PM
JIMBOX -----BINGO---


Quote:
Originally Posted by MTH View Post
You got that right.

To put you in a similar spot on the RPM band for your 33s as my guys are recommending for me on 33s, you'd need somewhere around 5.38s.
JIMBO
04-26-2011 04:02 PM
MTH
Quote:
Originally Posted by rics1997 View Post
Funny how off road shops can be so far off. I know yours is a manual but my off road shop was trying to talk me out of 4.88 for 33's. Said I would be more in line for 4.56 in that case a manual should be closer to 4.10.
You got that right.

To put you in a similar spot on the RPM band for your 33s as my guys are recommending for me on 33s, you'd need somewhere around 5.38s.
04-26-2011 03:59 PM
MTH
Quote:
Originally Posted by deathphoenix99 View Post
Good luck to you, and I see what you're saying. 2800 on the highway would be too high for a 6-banger, 2500 sounds more reasonable for the 3.8.

What's your 4wd low transfer case gearing? It's either 4:1 or the higher 2.? :1
I want to say 2.72:1. Rubicon JKs have the 4:1.

Thanks for all of your input.
04-26-2011 03:57 PM
rics1997 Funny how off road shops can be so far off. I know yours is a manual but my off road shop was trying to talk me out of 4.88 for 33's. Said I would be more in line for 4.56 in that case a manual should be closer to 4.10. Mainly went with 4.88 because I wanted Yukon gears and they didn't make 4.56 for D30's.

The non Rubicon transfer case is 2.72:1. MTH has the 2.72:1 like I do.
04-26-2011 03:45 PM
deathphoenix99 Good luck to you, and I see what you're saying. 2800 on the highway would be too high for a 6-banger, 2500 sounds more reasonable for the 3.8.

What's your 4wd low transfer case gearing? It's either 4:1 or the higher 2.? :1
04-26-2011 02:05 PM
MTH
Quote:
Originally Posted by deathphoenix99 View Post
First off, you have a modern transmission, which has over-drive. Over-drive is any gear ratio that has the output shaft spinning faster than the input shaft. Your 6th gear is overdrive while your 5th is a 1:1 ratio.
Fair enough. I'm used to using the term more colloquially to refer to a designated "overdrive," but yes, if I recall 6th gear in the JK is something like .84 or .85.

Quote:
Originally Posted by deathphoenix99 View Post
The 3.8 doesn't have low end power, so it should be ran at higher RPM's on the highway to be at maximum efficiency. Whenever you get larger tires, you want the RPM's to usually match what the stock RPM is at a given speed in a given gear, however, this is just a rough guideline depending what you plan to use your jeep for.
See there's the problem.

On the one hand, the 3.8's power continues to increase at about an even rate straight up until about 5k RPMs. So to optimize my power on 33s with a manual, I should regear right up to about 7.17s. Then I'd be turning right about 4400 RPM at ~70 mph and have loads of highway power. That's crazy of course and I wouldn't expect my engine to last long.

On the other hand, my stock performance at 70 mph on 32s is about 2000 RPM. I can't really duplicate that on 33s, but I could get closest by regearing to 3.73s. Of course, that wouldn't be worth the effort/money and in any event I do think the RPMs ought to be higher than they are in the stock form. Even in overdrive.

4.10s on 33s would have me at about 2500 RPMs at 70 mph in overdrive. That sounds about right. By contrast 4.56s would have me at about 2800 RPMs in overdrive. That sounds high, particularly since that's right about where I shift in my "around town" driving. I'm concerned I'd perpetually be reaching for 7th on 4.56s.

Quote:
Originally Posted by deathphoenix99 View Post
If you want to have a mix of both on-road and off-road, than a 3.73-4.10 would probably be fine for you.
Bingo. I love offroading and do it when I can, but I also commute 70 miles on the highway each day. I may very well be stuck here with no good option--overpay for 4.10s, stick with 32s, or go with 33s but be way undergeared. Grrr . . . .
04-26-2011 01:43 PM
deathphoenix99
Quote:
Originally Posted by MTH View Post
Yessir, but don't forget I have a manual--so I don't have overdrive. Though I suppose 6th gear is close. Are the folks you know with 4.56s on 33s TJ drivers or JK drivers? The engine/transmissions are different, so I'd expect the parameters for what's "ideal," "minimum," etc. would be different.
First off, you have a modern transmission, which has over-drive. Over-drive is any gear ratio that has the output shaft spinning faster than the input shaft. Your 6th gear is overdrive while your 5th is a 1:1 ratio.

And while the folks I know don't have JK's, I can assure you, the concept is the same, and actually they'd be better off with the numerically lower gears than you. The 3.8 doesn't have low end power, so it should be ran at higher RPM's on the highway to be at maximum efficiency. Whenever you get larger tires, you want the RPM's to usually match what the stock RPM is at a given speed in a given gear, however, this is just a rough guideline depending what you plan to use your jeep for. If you like to off-road a lot or tow, then a lower gear (>4.56 would be optimal). Don't forget that the tires weigh more, so this will bog down the engine more as well. IF your jeep is mainly an on-road vehicle with little to no offroad, 3.73 or even your 3.21 would be manageable, but again highway would suffer with 3.21. If you want to have a mix of both on-road and off-road, than a 3.73-4.10 would probably be fine for you.

Basically get the jeep to run within its powerband. Otherwise your mileage and power will suffer.
04-26-2011 01:31 PM
MTH
Quote:
Originally Posted by daggo66 View Post
That's odd since most 07's, especially automatics, came stock with 4.10.
Exactly. You can buy the OEM 4.10 R&P sets for a 2007 D35 and D44 from these guys. Not particularly expensive. You could also pay much more at Quadratec for OEM "Replacement Parts," where the chat guy believed they would fit into my 2010. Same axles, so why not?

However, speaking with the local 4WheelParts place (one of the few that do gears locally, and they do a lot), he was confident they wouldn't fit. He admitted he'd never tried it, but said his OEM "installation manual" recommended a different install kit for replacing the R&Ps in a 2007 than for replacing R&Ps in a 2010. To him, this meant it was unlikely 2007 R&Ps would fit properly in a 2010, regardless of whether both were using a D35 front and a D44 rear.

The only way to know for sure would be to buy 2007 4.10s, give it a go, and hope you can return the parts if they don't fit or bust up after 100 miles. Then pay the shop for labor for pursuing your little experiment that they told you would fail, and also buy new parts/labor to get it fixed. Not very appealing.
04-26-2011 01:17 PM
daggo66
Quote:
Originally Posted by MTH View Post

I think I'd be fine with 4.10s too, but they're apparently impossible to do with OEM parts and otherwise very expensive. I guess my debate at this point is whether to see what happens with 33s on 3.21s, to go straight to 4.56s with 33s, or to not even try and just stick with what I've got permanently. I don't ever see myself going to 35s.
That's odd since most 07's, especially automatics, came stock with 4.10.
04-26-2011 01:05 PM
MTH
Quote:
Originally Posted by deathphoenix99 View Post
4.10 is the minimum gearing you'd want for 33's, but with 4.56, you'd have a little more off the line power, especially when off-roading. I know plenty of people running 33's with 4.56 gearing as DD's and it's fine, you might actually gain some power as 3.21's and 32's seems like it'd be undergeared, especially in over drive.
Yessir, but don't forget I have a manual--so I don't have overdrive. Though I suppose 6th gear is close. Are the folks you know with 4.56s on 33s TJ drivers or JK drivers? The engine/transmissions are different, so I'd expect the parameters for what's "ideal," "minimum," etc. would be different.

Quote:
Originally Posted by daggo66 View Post
I have the same tires with a manual trans and 3.73. I think you'll be fine with 4.10 and 33's. However if you are ever considering 35's in the future, you should get the lower gears now.
I think I'd be fine with 4.10s too, but they're apparently impossible to do with OEM parts and otherwise very expensive. I guess my debate at this point is whether to see what happens with 33s on 3.21s, to go straight to 4.56s with 33s, or to not even try and just stick with what I've got permanently. I don't ever see myself going to 35s.
04-26-2011 12:47 PM
daggo66 I have the same tires with a manual trans and 3.73. I think you'll be fine with 4.10 and 33's. However if you are ever considering 35's in the future, you should get the lower gears now.
04-26-2011 12:35 PM
deathphoenix99 4.10 is the minimum gearing you'd want for 33's, but with 4.56, you'd have a little more off the line power, especially when off-roading. I know plenty of people running 33's with 4.56 gearing as DD's and it's fine, you might actually gain some power as 3.21's and 32's seems like it'd be undergeared, especially in over drive.
04-26-2011 12:30 PM
MTH
4.56s with 33s on a Manual Transmission?

Anyone out there with a manual transmission regeared to 4.56s with 33" tires on a daily driver?

I currently have a 4 door manual transmission with the stock 32" Rubi BFGs and the lowly 3.21 gears. I'm looking to go to 33s and would prefer to do so along with a regear to 4.10s, which looks about right according to this chart.

However, the shop I'm speaking with is virtually certain this is impossible with OEM parts (such as 4.10s for a 2007 JK X). Non-OEM 4.10 options are of course rare and twice as expensive as other gear ratios.

Interestingly, even if it was possible/affordable, the shop says it would still urge going to 4.56. According to them, manuals with 33s should go to 4.56, 35s to 4.88, and 37s to 5.13. Thus, even if I had already had 4.10s, they would still recommend 4.56s for 33" tires.

But to me it looks like my choices for 33s are wildly ungeared (stick with the 3.21s) or wildly overgeared (go to 4.56s). The shop says that's not true--4.56s would be a perfect daily driver.

Thoughts?

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