3.73 vs 4.10 - JeepForum.com

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post #1 of 20 Old 04-20-2013, 05:56 PM Thread Starter
firzout
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3.73 vs 4.10

I'm looking at replacing my pretty useless 2.72 gears in my Dana 30. I'm not sure if I'm better with 3.73 or 4.10s. I have a I6, T5 and 33" tires. I will be on pavement 99.9% of the time and I live in Fl where it's pretty flat. I want to drive on hwy (70 mph) and have the best MPG I can get.

What do you think and why?

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post #2 of 20 Old 04-20-2013, 05:58 PM Thread Starter
firzout
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Why have a locker on the front axle

I'm redoing my cj8. What advantage will I have by putting a locker on my Dana 30? I will not be going off road
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post #3 of 20 Old 04-20-2013, 06:04 PM
CJ51973
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Locker no, 4:10s if you have a 5 speed

Anything is possible if you don't know what you are talking about.
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post #4 of 20 Old 04-20-2013, 06:07 PM
CJ7KAHUNA
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Quote:
Originally Posted by firzout View Post
I'm looking at replacing my pretty useless 2.72 gears in my Dana 30. I'm not sure if I'm better with 3.73 or 4.10s. I have a I6, T5 and 33" tires. I will be on pavement 99.9% of the time and I live in Fl where it's pretty flat. I want to drive on hwy (70 mph) and have the best MPG I can get.

What do you think and why?
4.10
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post #5 of 20 Old 04-20-2013, 06:16 PM
Jeeprage
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Thanks guys. I'm in the same boat, although still wrapping up getting it together. Re-gearing will probably wait for next year. 4.11s it is for me.

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post #6 of 20 Old 04-20-2013, 06:57 PM
Frenimy
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I have 4.10's and a 4 speed and can still run 65mph so I would definitely get 4.10s and if you don't off-road then a locker won't help anything.

1981 CJ7 I6 258, NP435, Dana 300 Twin Sticks, AMC 20 & Dana 30 with Lockers, On board air, 33" X 12.50" tires
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post #7 of 20 Old 04-20-2013, 07:08 PM Thread Starter
firzout
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Thanks for the replies this far... I don't understand why my local buddies are telling me 3.73. Can you guys give me some more data?

If I run 4.10 what will my RPMs be at 70MPH in 5th gear??
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post #8 of 20 Old 04-20-2013, 08:56 PM
requiembell
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This should answer your questions about the gearing and speed ratios.

http://www.grimmjeeper.com/gears.html
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post #9 of 20 Old 04-20-2013, 08:56 PM
EgulAye
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There are some tools you can use to calculate what speed you would travel for a specified rpm, based on your transmission, axle ratio, tire size, etc... I have not used them, but they are here: http://www.offroaders.com/info/tech-...alculators.htm. I am sure there are other online tools like this, if you do a web search you are bound to find several.

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post #10 of 20 Old 04-21-2013, 07:03 AM Thread Starter
firzout
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Ok now I'm more confused... According to the calculator, if I run 32's my RPMs run higher then if I run 33" tires. How is that possible??

I'm also running lower RPMs with 3.73 then I would with 4.10 but everyone here is telling me to go with 4.10??

My jeep will be a DD with a lot of flat highway driving.
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post #11 of 20 Old 04-21-2013, 08:42 AM
titomars
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Quote:
Originally Posted by firzout View Post
Thanks for the replies this far... I don't understand why my local buddies are telling me 3.73. Can you guys give me some more data?

If I run 4.10 what will my RPMs be at 70MPH in 5th gear??
i have 4:10's with 33's and a T-5. RPM's @ 70 MPH will be 2,350 to 2,400

1981 Jeep CJ7 4.0 HO, AX-15, D300, D30, D44, SOA
1977 Chevrolet C/10 step side 454 TH400 3.73 posi
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post #12 of 20 Old 04-21-2013, 08:47 AM
Ripper3494
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your rpms are higher with smaller tires because they have to rotate more to do the same distance, same with the deeper gears 4.10s will give you higher rpms because your driveshaft will have to spin 4.1 times each time your tires spin once, vs 3.73 times each time your wheel spins once. the reason everyone is saying 4.10 is because it will give you a good balance of power and mpg on 33" tires. its all about finding a good balance of what you want. 3.73s will most likely give you better mpgs on the highway, but 4.10s will give you more power to get to highway speed

build thread:
http://www.jeepforum.com/forum/f22/9...-spud-1218315/
1994 yj stretched, locked and loaded - 6.0l vortec lq4, 4l60e, np231, Dana 44s 37" interco trxus m/t, 3.5" bds front leafs, double triangulated 4 link rear on xj front coils.
1997 ZJ limited - BONE stock
2003 tj - 4in skyjacker, 33" mickey thompsons
my on board alternator/welder write up
http://www.jeepforum.com/forum/f12/a...te-up-1301614/
my tj 1/2 doors on a yj write up
http://www.jeepforum.com/forum/f12/t...ation-1417686/
RC vs BDS
http://www.jeepforum.com/forum/f12/r...s-bds-1461555/
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post #13 of 20 Old 04-21-2013, 05:44 PM Thread Starter
firzout
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Thanks everyone for all the good info. So I believe it comes down to a few things... If I go with 4.10 gears I will get a little more power to reach my desired speed a little easier, but in return I'd run higher RPMs, which might cast me more fuel. If I go with 3.73 gears I might be a little sluggish reaching desired hwy speeds but run at lower RPMs which should same on the fuel.

Does this summarizes it correctly?
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post #14 of 20 Old 04-21-2013, 06:41 PM
Ripper3494
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Quote:
Originally Posted by firzout View Post
Thanks everyone for all the good info. So I believe it comes down to a few things... If I go with 4.10 gears I will get a little more power to reach my desired speed a little easier, but in return I'd run higher RPMs, which might cast me more fuel. If I go with 3.73 gears I might be a little sluggish reaching desired hwy speeds but run at lower RPMs which should same on the fuel.

Does this summarizes it correctly?
Yep. Depending on where your engine gets its power though 4.10s could potentially give you better MPGs. The engine has a sweet spot that it likes to run at

build thread:
http://www.jeepforum.com/forum/f22/9...-spud-1218315/
1994 yj stretched, locked and loaded - 6.0l vortec lq4, 4l60e, np231, Dana 44s 37" interco trxus m/t, 3.5" bds front leafs, double triangulated 4 link rear on xj front coils.
1997 ZJ limited - BONE stock
2003 tj - 4in skyjacker, 33" mickey thompsons
my on board alternator/welder write up
http://www.jeepforum.com/forum/f12/a...te-up-1301614/
my tj 1/2 doors on a yj write up
http://www.jeepforum.com/forum/f12/t...ation-1417686/
RC vs BDS
http://www.jeepforum.com/forum/f12/r...s-bds-1461555/
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post #15 of 20 Old 04-21-2013, 06:43 PM
Ripper3494
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This may help http://www.jeep4x4center.com/jeep-ti...atio-chart.htm

Sent from AutoGuide.com App

build thread:
http://www.jeepforum.com/forum/f22/9...-spud-1218315/
1994 yj stretched, locked and loaded - 6.0l vortec lq4, 4l60e, np231, Dana 44s 37" interco trxus m/t, 3.5" bds front leafs, double triangulated 4 link rear on xj front coils.
1997 ZJ limited - BONE stock
2003 tj - 4in skyjacker, 33" mickey thompsons
my on board alternator/welder write up
http://www.jeepforum.com/forum/f12/a...te-up-1301614/
my tj 1/2 doors on a yj write up
http://www.jeepforum.com/forum/f12/t...ation-1417686/
RC vs BDS
http://www.jeepforum.com/forum/f12/r...s-bds-1461555/
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