Gearing preference for 2016 JKU Sport 6 speed - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 14 Old 03-10-2016, 07:37 AM Thread Starter
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Gearing preference for 2016 JKU Sport 6 speed

Hey guys, new member here. I'm ordering a 2016 JKU 6 speed with the 3.73 gears, and right now I'm leaning towards 35" Duratracs and XD Striker wheels with a 3" lift. This is a DD with limited offroading to get to my hunting lease. I see a lot of threads about recommending to switch out gearing to 4.56 or even 5.13-- but most of those posts seem to be before the switch to the 3.6 engine that has more HP. Can I get some thoughts on 3.73 vs. 4.56 gearing on a DD 6 speed manual? It's tough for me to decide without actually driving something in 4.56-- I fear that 4.56 gearing in a DD manual means 1st gear is going to be nothing more than a creeper gear (which is okay I guess)
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post #2 of 14 Old 03-10-2016, 11:20 AM
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4.56 would be perfect - don't forget to recalibrate the computer

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post #3 of 14 Old 03-10-2016, 11:50 AM
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4.56 is a good middle of the road balance between on and offroad, for 35s and a 6 speed. Since you wont be doing a lot of heavy rock crawling, I wouldn't go any deeper. You should still get plenty of use out of first gear as well.

A big reason for regearing is to actually get the jeep to drive and act closer to the way it was meant to, with the factory gearing and tire size. When you go up in tire size, you want to go with a lower gear to not only improve offroad capability, but also maintain on road manners.


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post #4 of 14 Old 03-10-2016, 05:39 PM
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Originally Posted by estark573 View Post
Hey guys, new member here. I'm ordering a 2016 JKU 6 speed with the 3.73 gears, and right now I'm leaning towards 35" Duratracs and XD Striker wheels with a 3" lift. This is a DD with limited offroading to get to my hunting lease. I see a lot of threads about recommending to switch out gearing to 4.56 or even 5.13-- but most of those posts seem to be before the switch to the 3.6 engine that has more HP. Can I get some thoughts on 3.73 vs. 4.56 gearing on a DD 6 speed manual? It's tough for me to decide without actually driving something in 4.56-- I fear that 4.56 gearing in a DD manual means 1st gear is going to be nothing more than a creeper gear (which is okay I guess)
Have you ordered it? I haven't been terribly disappointed on the street with my stock 4:10's and 35" MTR's.

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post #5 of 14 Old 03-16-2016, 07:39 AM Thread Starter
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I have not ordered it yet. I am still debating on paying the $695 for the factory 3.73 gears or getting the standard 3.21 gearing and then paying $1500 for the local shop to put in 4.56. I know the duratracs run small, and the outside diameter of the 315/70/R17s is 34.4". So I think I could get away with the 3.73 gears for now (duratracs being a little less than 35" and lighter than others), but I'm still on the fence.
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post #6 of 14 Old 03-16-2016, 08:01 AM
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If you are absolutely going to put 35's on it, order it stock and put the 4.56's in it when it shows up.


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post #7 of 14 Old 03-16-2016, 08:21 AM
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There is a middle ground to your middle ground. 4.88s. 4.56s with 35s gives you about stock gearing as a stock rubicon on 32s. Each step is around 200-250RPM increase in 6th gear.

Personally, I have a '12 JK Rubicon 2Dr 6speed with 35s. It currently has the stock 4.10s. It drives ok. I wouldn't pay to put 4.10s in though, I'm planning to swap them out for 4.88s as I tow and go off road. Currently, 4High is about useless, as starting off in anything mucky is a lesson in clutch abuse.

Also to consider, I believe with 3.21s, you have to purchase new carriers when upgrading. You don't have to do that with 3.73. Not sure how much the option is or how much the carriers are, but it's something to think about. Also, you could actually sell the 3.73s to someone after you remove them. No one wants to go to 3.21s.
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post #8 of 14 Old 03-16-2016, 08:42 AM
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There is a middle ground to your middle ground. 4.88s. 4.56s with 35s gives you about stock gearing as a stock rubicon on 32s. Each step is around 200-250RPM increase in 6th gear.

Personally, I have a '12 JK Rubicon 2Dr 6speed with 35s. It currently has the stock 4.10s. It drives ok. I wouldn't pay to put 4.10s in though, I'm planning to swap them out for 4.88s as I tow and go off road. Currently, 4High is about useless, as starting off in anything mucky is a lesson in clutch abuse.

Also to consider, I believe with 3.21s, you have to purchase new carriers when upgrading. You don't have to do that with 3.73. Not sure how much the option is or how much the carriers are, but it's something to think about. Also, you could actually sell the 3.73s to someone after you remove them. No one wants to go to 3.21s.
HAHA! I have 37's with 4.10's. I just skip 4H right now, the only way to make it work it to smoke the clutch and red line the engine.

Soon to have 4.88's so that I can use 4H again, driving on snow/ice in 4L is painful when it is needed.
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post #9 of 14 Old 03-17-2016, 10:42 AM
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Gearing

Wow, you opened a can of worms with this question. It's like asking which workout routine is the best. You will get all different kinds of answers. All I can say is do your research and make your own decision based off how you are going to drive it. I drank the cool-aid one time and went to the 5:13s and hated them. Sure it was fine on flat ground and had so much torque you could pull a house, but you could not get over 45 MPH in the mountains unless you wanted your taq to scream. I had an old timer that does gears for a living tell me on time that a very reliable rule of thumb is the use proportionate values when deciding on gearing. For example. If your tire size is lets say 29s and you want to goto 35s it's roughly a 20.5% increase, so your gears should roughly be the same percentage...so 3:73 to 4:56 is roughly a 22% increase...to 4:88 is a 30% increase. The goal is to try and stay close to the increase of your tires. when you get close check the chart and see what the RPM numbers say, then go drive your jeep and cross reference a certain speed before swap with the chart after swap. Are they close to the same numbers? If they are then you found your gear set. Make sense? The engineers have already done all the math involved, why reinvent the wheel. Good luck with your choice.

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post #10 of 14 Old 03-17-2016, 01:10 PM
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The only problem with that theory is. that doesn't account for increase unsprung weight. The stock tires weight 47 lbs. 35" Nito's MG's are 81 lbs. 136 lbs of extra rotational mass and unsprung weight is grossly gonna affect acceleration, cornering and ride comfort. Selecting the right gears and maintaining correct acceleration is going to be based on more than just a generic percentage increase or decrease in gear or tire size.


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post #11 of 14 Old 03-17-2016, 10:32 PM
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With the untold number of tire and wheel combinations out there I just don't believe that the RPM chart we all use has taken into account Unsprung weight and rotational force involved in each tire wheel scenario. Unsprung weight is thrown around alot, but it actually accounts for all components like "wheel axles, wheel bearings, wheel hubs, tires, and a portion of the weight of driveshafts, springs, shock absorbers, and suspension links". We have all changed these components and havent gave a second thought to the unsprung weight increase. As for the rotational mass, well, now it goes into Physics and a whole other can of worms that just don't need to be messed with for the average wheeler. For what the OP wants that rule of thumb I passed on will work just fine for him. I have done many gear swaps myself and wheeled varying terrain and it has worked for me so far, so for me personally, I am sticking with it.

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post #12 of 14 Old 03-18-2016, 03:41 AM
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Your 16 with a standard will be fine and a pleasure to drive with 4.56 gears and 35" tires.

I run 4.88s on my 13 with 35's and am happy with it for my use. I can still run the interstate at 70-80 mph without it being wound too tight but if I were to run those speeds daily 4.56s would be a better choice. My daily drive consists of 45-60mph speeds amd the 4.88s are perfect in that range and typically run in 5th or 6th gear with ease.
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post #13 of 14 Old 03-18-2016, 08:27 AM
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Originally Posted by rutdigger View Post
With the untold number of tire and wheel combinations out there I just don't believe that the RPM chart we all use has taken into account Unsprung weight and rotational force involved in each tire wheel scenario. Unsprung weight is thrown around alot, but it actually accounts for all components like "wheel axles, wheel bearings, wheel hubs, tires, and a portion of the weight of driveshafts, springs, shock absorbers, and suspension links". We have all changed these components and havent gave a second thought to the unsprung weight increase. As for the rotational mass, well, now it goes into Physics and a whole other can of worms that just don't need to be messed with for the average wheeler. For what the OP wants that rule of thumb I passed on will work just fine for him. I have done many gear swaps myself and wheeled varying terrain and it has worked for me so far, so for me personally, I am sticking with it.
eh, maybe for some drivers, it may not matter. Especially if they get light weight tires by coincidence. However... if someone does go that route and ignore big changes in rotational mass and unsprung weight, don't be the guy who complains about needing to stop for gas more often, crap acceleration and having problems going up a 10% or 12.5% grade on the highway.


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post #14 of 14 Old 03-26-2016, 09:56 PM
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4.56 would be perfect - don't forget to recalibrate the computer
4.56 should do ya. I am running 4.10's with 37" tires currently... Does fine mostly, just can't hold 60 on a hill. 4.88's get installed next week, I am looking forward to back to 'stock' style performance, and regaining my use of 4 Hi.

Currently 4 Hi can be used if I want to abuse my clutch and make it smoke, otherwise it is 4 Lo only.
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