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Topic Review (Newest First)
12-21-2012 08:37 AM
Daniel_M IMO, if you are intent on going with new axles, hold off on the re-gear. It is a waste of money if in a year you scrap them. However if you don’t wheel extremely hard every weekend, the D30 will be just fine. My guess is you are real careful since it is a DD. A D30, open on 37’s will hold up. Gusset at the least, sleeve or truss if you want. No need to clamshell and all that. FWIW the D30 outer tubing is the same as the D44, the real weak link is the ring and pinion. A 2012, open diff and 37’s I would go with 4.88 gear set.

Personally I would reinforce the D30, run 37’s and 4.88’s and call it a day. Leave the OEM axle shafts in place since they are easier and cheaper to replace than a R&P, have spares. The OEM shaft will go before the R&P does, chromoly aftermarket ones will not give and you will grenade your gears. I am currently running 35’s on my D30, 5.13’s and am locked. I will be putting 37’s on when my 35’s wear out and I have no 2nd thoughts about it.

-Dan
12-20-2012 03:28 PM
JeepHerz
Quote:
Originally Posted by makotoshishio View Post
You are right about that, it is how you wheel. I have 33's with D30 and D44 and a 4.88 ratio. I plan on going to 37's but I'll will keep my D30 until it dies. When I get the 37's I'll regear to 5.35 (not sure right now if this is the correct number after 5.13) and install ARB locker on the D44.

Regearing is easy, you only need the right tools, I don't so I have to pay for it. Around $250 per each side.

Here is to hoping its easy. My husband is going to attempt the rear first and see if anything goes horribly wrong before attempting the fronts. He's re-built trannys and engines so I think it will be fine.
However I'll check back in a few months. I might just pony up the cash for the (installer) warranty. Just angry I have to spend any cash on this since I messed up and got 3.21s to start. The last time I hit the trail I got really sick of watching everyone else "crawl" over rocks while I lurched and spun.
12-20-2012 02:54 PM
makotoshishio You are right about that, it is how you wheel. I have 33's with D30 and D44 and a 4.88 ratio. I plan on going to 37's but I'll will keep my D30 until it dies. When I get the 37's I'll regear to 5.35 (not sure right now if this is the correct number after 5.13) and install ARB locker on the D44.

Regearing is easy, you only need the right tools, I don't so I have to pay for it. Around $250 per each side.



Quote:
Originally Posted by pluke the 2 View Post
i got 513s with a dana 30 and 37's with arb lockers front and rear no issues here............

dana 44's break
dana 60's break

my dana 30 hasnt broken.

its all about how you wheel

12-20-2012 02:48 PM
chrisfp88 thanks
12-20-2012 02:37 PM
bo9roadking
Quote:
Originally Posted by chrisfp88 View Post
But for me in Colorado it looks like 4.88 may be the best
Quite true. The higher elevation will require more pedal to get over those passes. You will need that gearing to help stay in the engine's sweet spot for your application with less transmission gear hunting.

That is why some people prefer 4.88 or 5.13 gears. They may not be commuting on the highway or live in an area with flat terrain, which is why I'm getting 4.56 gears. People choosing the other gear options might do less highway driving and more offroading at slower speeds or do a lot of towing and need to keep the rpms up higher. They need the engine sweet spot with the torque to come on quicker.

Since I have a Rubicon, I still have the slow offroad crawling capability with my 4:1 transfer case, but with 4.56 gears, I won't be running as high of an rpm on the highway burning extra fuel.
12-20-2012 01:19 PM
chrisfp88
Quote:
Originally Posted by bo9roadking View Post
Yes, so you don't want to overgear. You don't want to undergear either because if your rpms are too low, you use more gas pedal to try and get going. The stop and go will decrease the mileage too because you have to use more pedal to take off. That is why people with larger tires that don't change their gears will lose gas mileage. You have to get the gears that put the rpms back into the engines sweet spot.
But for me in Colorado it looks like 4.88 may be the best
12-20-2012 12:55 PM
bo9roadking
Quote:
Originally Posted by chrisfp88 View Post
And so higher rpms leads to decreased fuel economy right?
Yes, so you don't want to overgear. You don't want to undergear either because if your rpms are too low, you use more gas pedal to try and get going. The stop and go will decrease the mileage too because you have to use more pedal to take off. That is why people with larger tires that don't change their gears will lose gas mileage. You have to get the gears that put the rpms back into the engines sweet spot.
12-20-2012 12:19 PM
JeepHerz
Quote:
Originally Posted by bo9roadking View Post
That is the correct chart, but your rpms are based on your actual tire size when mounted on the Jeep. A typical 35" tire is only 34" when mounted with the Jeep's weight on it, so you would need to look at the 34" tire size on the chart.

I'm not sure how you came up with 2700 rpms at 70 for a 35" tire and 4.56 gears. The chart shows that combination to be about 2544 rpms. With my current 4.10 gears and 35" tires, my rpms are pretty close to the chart numbers at 70 mph.

I don't have 35s now.
Sorry- meant 37s.
12-20-2012 12:17 PM
chrisfp88
Quote:
Originally Posted by bo9roadking View Post
With 3.73 gears and 32" tires, the new 4.56 gearing and 37" tires would be about 130 rpms higher than stock at 70 mph.

With 3.73 gears and 35" tires, the new 4.56 gearing and 37" tires would be about 325 rpms higher that what you are running now at 70 mph.
And so higher rpms leads to decreased fuel economy right?
12-20-2012 12:10 PM
bo9roadking
Quote:
Originally Posted by JeepHerz View Post
I THINK this is the right gear chart. I know there were several running around.
Nothing to add...just researching. Doing 4.56s myself probably- but I'll stick to 35s. I can hardly get in the Jeep as it is. If you believe the chart- you'd be around 2700 RPMs at 70. (But I am in 33/34s now and at 70 I am not at 1900 RPMS)
That is the correct chart, but your rpms are based on your actual tire size when mounted on the Jeep. A typical 35" tire is only 34" when mounted with the Jeep's weight on it, so you would need to look at the 34" tire size on the chart.

I'm not sure how you came up with 2700 rpms at 70 for a 35" tire and 4.56 gears. The chart shows that combination to be about 2544 rpms. With my current 4.10 gears and 35" tires, my rpms are pretty close to the chart numbers at 70 mph.
12-20-2012 12:02 PM
bo9roadking
Quote:
Originally Posted by chrisfp88 View Post
Would that be reduced to around 250 and 300 in your math as I'm actually running 3.73's right now? Thanks
With 3.73 gears and 32" tires, the new 4.56 gearing and 37" tires would be about 130 rpms higher than stock at 70 mph.

With 3.73 gears and 35" tires, the new 4.56 gearing and 37" tires would be about 325 rpms higher that what you are running now at 70 mph.
12-20-2012 11:56 AM
JeepHerz I THINK this is the right gear chart. I know there were several running around.
Nothing to add...just researching. Doing 4.56s myself probably- but I'll stick to 35s. I can hardly get in the Jeep as it is. If you believe the chart- you'd be around 2700 RPMs at 70. (But I am in 33/34s now and at 70 I am not at 1900 RPMS)
12-20-2012 10:28 AM
chrisfp88
Quote:
Originally Posted by bo9roadking View Post
If you have a 3.6 Pentastar and are concerned about mileage, stick with 4.56 gears, especially if you do any highway driving. The 4.88 and 5.13 gears are better if you are primarily crawling offroad, but not so good for a daily driver.

If you go with 4.56 gears and 37" tires, you will be running 500 rpms higher than you were with stock 32" tires and 3.21 gearing and about 600 rpm higher than 35" tires and 3.21 gearing at 70 mph.
Would that be reduced to around 250 and 300 in your math as I'm actually running 3.73's right now? Thanks
12-20-2012 09:05 AM
bo9roadking If you have a 3.6 Pentastar and are concerned about mileage, stick with 4.56 gears, especially if you do any highway driving. The 4.88 and 5.13 gears are better if you are primarily crawling offroad, but not so good for a daily driver.

If you go with 4.56 gears and 37" tires, you will be running 500 rpms higher than you were with stock 32" tires and 3.21 gearing and about 600 rpm higher than 35" tires and 3.21 gearing at 70 mph.
12-17-2012 01:44 PM
chrisfp88
Quote:
Originally Posted by 3JKs1H1 View Post
You should buy a second jeep. The more trail capable you make it, the less DD it will become.

37"s will not balance as well or provide the quickness that a 32" tire will.
The higher you lift your jeep, the less it wants to corner at speed. Big tires wear the suspension much faster.

Besides, if you build a trail rig, you won't feel obligated to wash it.
I can't afford a second Jeep. I still live at home. Moving out is more important than an another piece of debt.
12-17-2012 01:26 PM
3JKs1H1 You should buy a second jeep. The more trail capable you make it, the less DD it will become.

37"s will not balance as well or provide the quickness that a 32" tire will.
The higher you lift your jeep, the less it wants to corner at speed. Big tires wear the suspension much faster.

Besides, if you build a trail rig, you won't feel obligated to wash it.
12-17-2012 01:23 PM
pluke the 2 if i had to do it again. i wouldn't spend the money again on the dana 30. but for how little i wheel, this was the most economical benefit for me in the short run.

for a 2012 jku with automatic tranny, with 37's, i'd gear her to 513's. my commutes are short and my .5 wheeling on average a month, low gearing is definitely more noticeable for trails versus daily driving.
12-17-2012 01:20 PM
chrisfp88
Quote:
Originally Posted by pluke the 2 View Post
i got 513s with a dana 30 and 37's with arb lockers front and rear no issues here............

dana 44's break
dana 60's break

my dana 30 hasnt broken.

its all about how you wheel

thanks pluke. I'm going to reinforce it and leave the 30 open. I really want a re-gear current power is lacking. I might as well do 37's with having to replace my tires this year.
12-17-2012 01:11 PM
steve76t For a daily driver 35's and 4.56's would work great. With 37's the dana 30 may have issues especially with 4.88 gears. 5.13's may just be too low for the 30 and may break easily with 37's. If it were me, I'd probably stick with the 35's & 4.56's for now & upgrade gear ratio and tires when you have the front 44 ready to go in. Regardless of what you choose, gas mileage probably wont be improved much if any.
12-17-2012 01:08 PM
xcoaste I wouldn't bother regearing now. Wait until you have the rig the way you want it. Doing gears you are looking at $1200+.
12-17-2012 12:40 PM
chrisfp88 also do a huge amount of highway driving over 65 and mountainous roads here in Colorado
12-17-2012 12:39 PM
chrisfp88
4.56, 4.88, or 5.13

Ok so I'm trying to figure out which gearing will be optimal. Here's the back story:

Here's my plan and let me know what you all think stick with the front hp Dana 30 for the first year. First off I don't take Impossible lines. I'm a careful wheeler, mostly because this is my daily driver. I would like to do gussets and sleeves, potentially tubes. Re-gear, but leave the diff open. Plan is to re-gear to 4.56 or 4.88. Lock the rear 44. Run this setup for one summer. Then put a Dana 44 up front. Run it like that for the next summer and finally put a Dana 60 in the rear after that.

The whole reason I am thinking about going up to 37's is that I have to get new tires this summer is because I trashed my 35's with a bent tie rod. I have to switch tires and the monetary difference between the 2 is minimal.

I wanna try to get great fuel economy or at least better then the 12mpg I'm getting now, if that is even possible. It is an automatic as well.


Thanks

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