3.21 or 4.10 ??? - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > JK Wrangler Technical Forum > 3.21 or 4.10 ???

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineRockridge 4WD IS Taking Zone Offroad Suspension Lift Kits Rough Country Jeep Suspension Deals at Rockridge 4WD!

Reply
Unread 12-17-2006, 10:00 PM   #1
hpjaz
Registered User
 
Join Date: Dec 2006
Location: Dallas, Texas
Posts: 7
3.21 or 4.10 ???

Thought we needed a thread specifically focused on rear axle gear ratio. (This is also my 1st post... so be nice.) Most of the outside reviews reference at least some mild disappointment in the new engine's lack of power. Higher gear ratios can fix that but usually at a cost: MPG. Most, if not all, of us (whether we admit it or not) spend the vast majority of the time in "city" or "highway" driving conditions. As such, we do sometimes need to get out of our own way.

The 4 speed auto and the Rubi have no choice in gear ratios as the 4.10 is the standard these models. Only the 6 speed manual comes standard with the 3.21. The 4.10 is a $50.00 upgrade. It would be nice to keep the 3.21 and possibly get better MPG.


For daily use, is the 4.10 a "must" upgrade for the 6 speed manual?
Or, does the 3.21 get the job done around town?
Any real world MPG comparison between the two?

hpjaz is offline   Reply With Quote
Unread 12-18-2006, 02:58 AM   #2
Poor Boy
All Around Nice Guy
 
Poor Boy's Avatar
2007 JK Wrangler 
 
Join Date: Apr 2006
Location: Annapolis
Posts: 1,688
get the 4.10 ratio. if you get the 3.21, and throw tires on there any bigger than a pizza cutter, you'll be sorry. you'll be in the shop, paying some dude 500 bucks an axle for install. nevermind the cost of the parts.
__________________
Quote:
Originally Posted by Hank Venture
It's like someone with a fever is yelling at my pants!
Feed my girlfriend.

Follow my girlfriend

Brew what you drink, drink what you brew

USN Hull number 54
Poor Boy is offline   Reply With Quote
Unread 12-18-2006, 05:50 AM   #3
UTAH
Registered User
 
Join Date: Jul 2003
Location: Salt Lake City
Posts: 1,113
Quote:
Originally Posted by hpjaz
For daily use, is the 4.10 a "must" upgrade for the 6 speed manual?
Or, does the 3.21 get the job done around town?
I've got the 6 speed and the 3.21 axle and was worried about how the vehicle would respond with 33's on it. I figured I'd want to upgrade to the 4.10s. After driving the vehicle for two months around town, on the freeway, and in snow, ice, and dirt - I'm sticking with the 3.21s.

For starters, the 6 speed has a pretty low first gear. It's low enough that, unless I'm on a hill, I don't give it throttle when letting out the clutch from a stop. And, the gears are grouped relatively closely – allowing you to keep RPMs just where you want ‘em.

With the stock tires I was turning 2300 RPMs at 70 MPH in 6th. With the 33's I'm at 2400 RPMs at 70 in 5th - which is the gear of choice now for freeway cruising. (note: all figures corrected for tire change) It'll still pull 6th with the 33s, but at speeds of around 80 MPH+ to keep up the RPMs - I think it's a bit much for safety and for legal reasons.

As I've opined in other threads, I think the JK has an easier time at speed due to improved aerodynamics. My 4.0 TJ, which has the 4.10s and 33's, strains to keep up with traffic above 70 MPH and pretty much hits a wall about 80 MPH. The 3.8 JK with 3.21s and 33's I thought would do worse on the freeway - but it actually does better. I don't know what the top speed of my JK is, but I can tell you it's not 85 MPH - because when I was at that speed on the freeway last week I still had power left to accelerate.

Now, admittedly, my JK has an advantage over my TJ that's pretty obvious - the TJ is an auto and the JK is a stick. The ability to match the best gear to engine speed and conditions always goes to the 6-speed and not the auto. However, given that, I would think the TJ's higher axle ratio of 4.10 would more than compensate in performance. It doesn't. Both vehicles have 33's and the JK is quicker, faster, quieter, and more fuel efficient (TJ = 15 MPG, JK = 18 MPG).

As I continue to say - I wonder if people who are commenting that the 3.8 V6 is a dog (compared to the 4.0 I6) have actually spent much time driving both. If the 3.8 is lacking something in comparison - I've yet to see it. Quite the contrary, I've found the 3.8 to be more efficient and effective in every day use.

Bill
__________________
2013 JK Sahara 2-dr, 6 speed
2014 KL Cherokee Trailhawk
UTAH is offline   Reply With Quote
Unread 12-18-2006, 10:33 AM   #4
hpjaz
Registered User
 
Join Date: Dec 2006
Location: Dallas, Texas
Posts: 7
Hey UTAH, thanks for the info.
Great detail. Sounds like you really love your new 07.
hpjaz is offline   Reply With Quote
Unread 12-18-2006, 11:04 AM   #5
fraynes1
Registered User
 
Join Date: Nov 2006
Location: Ontario
Posts: 69
I've got the 6sp with 3.21, what about towing. I never researched it before purchasing enough (totally my fault).

I don't mean a camper trailer or another vehicle, just a small utility trailer for the odd dump run, picking stuff up from stores. The heaviest thing I will be pulling is firewood. About a face cord at the max. and about 10 trips of these per year within 15 km's from home. Is this too much for the 3.21's?

Thanks
__________________
[FONT="Arial"]2007 Jeep Unlimited X 6 speed, freedom top. 1st Jeep ever, bought on 24 November 2006. Red in color.[/FONT]
fraynes1 is offline   Reply With Quote
Unread 12-18-2006, 01:08 PM   #6
hpjaz
Registered User
 
Join Date: Dec 2006
Location: Dallas, Texas
Posts: 7
If your towing and tongue weights aren't excessive, occasional light towing should not be a problem. However, I would re-visit the service manual specs for both the towing and tongue weight limits.
How is the performance with the 6 speed and 3.21?
Any idea about MPG for city and highway?
hpjaz is offline   Reply With Quote
Unread 12-18-2006, 01:23 PM   #7
UTAH
Registered User
 
Join Date: Jul 2003
Location: Salt Lake City
Posts: 1,113
Dang - I almost forgot...

Welcome to the forum, hpjaz.

Bill
__________________
2013 JK Sahara 2-dr, 6 speed
2014 KL Cherokee Trailhawk
UTAH is offline   Reply With Quote
Unread 12-18-2006, 06:23 PM   #8
SecondTJ
Registered User
2000 TJ Wrangler 
 
Join Date: Sep 2006
Location: Illinois
Posts: 5,321
Quote:
Originally Posted by fraynes1
I've got the 6sp with 3.21, what about towing. I never researched it before purchasing enough (totally my fault).

I don't mean a camper trailer or another vehicle, just a small utility trailer for the odd dump run, picking stuff up from stores. The heaviest thing I will be pulling is firewood. About a face cord at the max. and about 10 trips of these per year within 15 km's from home. Is this too much for the 3.21's?

Thanks
Max. towing on 3.21 gears is only 1000 lbs.
__________________
'00 Sport. 5-speed, Detroit TrueTrac Dana 44 rear, Detroit TrueTrac front, 4.10's, 2" RE BB, OME shocks, 31" BFG MT, JKS Quicker Disco's, Borla

'99 Z28 M6, some goodies
'94 'Vette, A4 all stock
SecondTJ is offline   Reply With Quote
Unread 12-18-2006, 06:41 PM   #9
2K1TJ
Registered User
 
Join Date: Mar 2004
Posts: 57
I have the 6 speed w/3.21's and 305/70/17's (34's). Wish I'd waited for one w/ the 4.10's . The 3.21's are OK as long as you don't plan on putting on bigger tires.

Like was mentioned earlier, the low gear of the 6 sp makes it tolerable, but 6th gear is pretty much useless unless you're on the freeway at high speeds.
2K1TJ is offline   Reply With Quote
Unread 12-19-2006, 06:18 PM   #10
2k2wranglerx
Registered User
2003 TJ Wrangler 
 
Join Date: Nov 2002
Location: pittsburgh, Pennsylvania
Posts: 1,234
Quote:
Originally Posted by 2K1TJ
I have the 6 speed w/3.21's and 305/70/17's (34's). Wish I'd waited for one w/ the 4.10's . The 3.21's are OK as long as you don't plan on putting on bigger tires.

Like was mentioned earlier, the low gear of the 6 sp makes it tolerable, but 6th gear is pretty much useless unless you're on the freeway at high speeds.
ya i wish i had gotten 4.10's . . . . but i'm going 4.56's when i ditch the 305's and go to 315's (35's).

that being said, the 3.21's are tolerable. i have no issues with power and i get 6th on the highway.
__________________
03 tj. 4" FT LA, Solid 60, arb's, kilby, mastercrafts, caged, moab fab fenders, LED everything, etc.
2k2wranglerx is offline   Reply With Quote
Unread 12-19-2006, 10:23 PM   #11
fraynes1
Registered User
 
Join Date: Nov 2006
Location: Ontario
Posts: 69
When you guys are talking about getting 4.56's are you taking the 4.10's out? Sorry just don't know this stuff.

If that's the case if I drive with the 3.21's and they go tits up on my can I just replace them with 4.10's or bigger?

If so any idea how much this costs?

Thanks
__________________
[FONT="Arial"]2007 Jeep Unlimited X 6 speed, freedom top. 1st Jeep ever, bought on 24 November 2006. Red in color.[/FONT]
fraynes1 is offline   Reply With Quote
Unread 12-19-2006, 11:45 PM   #12
SecondTJ
Registered User
2000 TJ Wrangler 
 
Join Date: Sep 2006
Location: Illinois
Posts: 5,321
Quote:
Originally Posted by fraynes1
When you guys are talking about getting 4.56's are you taking the 4.10's out? Sorry just don't know this stuff.

If that's the case if I drive with the 3.21's and they go tits up on my can I just replace them with 4.10's or bigger?

If so any idea how much this costs?

Thanks
yes it means taking the 4.10s out and swapping in 4.56s

re-gearing generally costs ~$1000, with parts & labor. Its MUCH cheaper to just pony up the $50 for the factory 4.10s if thats all your going to need
__________________
'00 Sport. 5-speed, Detroit TrueTrac Dana 44 rear, Detroit TrueTrac front, 4.10's, 2" RE BB, OME shocks, 31" BFG MT, JKS Quicker Disco's, Borla

'99 Z28 M6, some goodies
'94 'Vette, A4 all stock
SecondTJ is offline   Reply With Quote
Unread 12-20-2006, 01:46 AM   #13
Poor Boy
All Around Nice Guy
 
Poor Boy's Avatar
2007 JK Wrangler 
 
Join Date: Apr 2006
Location: Annapolis
Posts: 1,688
Quote:
Originally Posted by fraynes1
When you guys are talking about getting 4.56's are you taking the 4.10's out? Sorry just don't know this stuff.

If that's the case if I drive with the 3.21's and they go tits up on my can I just replace them with 4.10's or bigger?

If so any idea how much this costs?

Thanks
also, with the TJ's, and i imagine with the JK's as well, you have to replace the carrier for that big a leap. tj's were 3.55 and lower, and 3.73 and higher carriers in our stock axles. just something to figure in the cost. regearing is expensive...
__________________
Quote:
Originally Posted by Hank Venture
It's like someone with a fever is yelling at my pants!
Feed my girlfriend.

Follow my girlfriend

Brew what you drink, drink what you brew

USN Hull number 54
Poor Boy is offline   Reply With Quote
Unread 12-20-2006, 05:41 PM   #14
hpjaz
Registered User
 
Join Date: Dec 2006
Location: Dallas, Texas
Posts: 7
fraynes1:
Any idea what your average MGP has been? Some are reporting well over 20 (though I', certain there has to be quite a bit of highway miles in those figures.
hpjaz is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.