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Question regarding gear swaps - Yukon 4.88 gears?

Bekser

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Hi all,

I have a 21 JLR 6speed on 35s. will be lifting (2.5" RK X-factor w/ fox shocks) soon as well. Initially, I was not planning on swapping out gears since most everyone reported no need to with 4.10 gears on a Rubi. However, I am strongly considering one on the 6speed. It's not a bad drive, but compared to the 33"s it's a bit sluggish, especially at 6. For reference, I'm at a steady 1970-1990 RPM @ 70MPH.

I'm thinking some Yukon 4.88 gears (I think 4.56 might not be enough). Does anyone have any insight or any kit recommendations?

Thanks
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ChromeToaster

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Everyone agrees the 6speed will benefit with a gear swap Id go to 4.88 or even 5.13. I have a 6speed 21 rubicon as well and im saving up for 5.13s and a metal cloak 3.5 lift with some 37s it will take a small hit on mpg but the power will be back and have a slightly better crawl ratio as well.

Stock Rubicon 33's on 4.10 with the 6 speed is already bad as far as I'm concerned have to drop to 4th for any hills in order to keep 65 or 70mph.
 

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@rustyshakelford has both an auto and manual Rubicons. I remember his postings about the auto being more resistant to the need of a regear. If memory serves, he put 5.13's in the manual.
 

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There really are two options: don’t use 6th, or regear.
 

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Definitely re-gear. Definitely do 4.88. You will be over geared with 35s and setup perfectly for 37s in the future. Yukon makes good stuff, I have Dana gears and Yukon master kits.
 

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Maverick909

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man yall dont know sluggish until you try driving rubi 33's with sport 3.45 gears and the 6 speed. Just installed rubi axles with 4.10 my god what a difference. ill be adding 35's in the next year or so when my tires wear out. but will not re-gear. I wouldnt recommend 4.88 with 35's and the 6 speed. with 37's and 4:88's rolling on flat in 6th gear at 2400 rpm your looking closer to 2700 @70 with 35's real world. 4.56 is the number for 35's IMO

https://www.jlwranglerforums.com/fo...3-tires-in-6th-gear-72mph.58253/#post-1257240
 

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man yall dont know sluggish until you try driving rubi 33's with sport 3.45 gears and the 6 speed. Just installed rubi axles with 4.10 my god what a difference. ill be adding 35's in the next year or so when my tires wear out. but will not re-gear. I wouldnt recommend 4.88 with 35's and the 6 speed. with 37's and 4:88's rolling on flat in 6th gear at 2400 rpm your looking closer to 2700 @70 with 35's real world. 4.56 is the number for 35's IMO

https://www.jlwranglerforums.com/fo...3-tires-in-6th-gear-72mph.58253/#post-1257240
Yeah I have a 6 speed on 285/75/r17s, stock sport 3.45s, highway life isn't great. The clutch already occasionally hates me crawling or backing into my weird parking space (I live in a neighborhood with very old houses). Recently took a promotion in another location but haven't moved yet, 200km a day makes the gears even more of a priority. Fuel economy and drivability would be so much better. Thinking 4.88s or 5.13s even, gives me room to grow and I'd prefer effectively having a granny gear 1st to a 6th I never really use. Just torn on the whole m186 front situation, do I even spend money on it? Decisions need to be made...
 

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Yeah I have a 6 speed on 285/75/r17s, stock sport 3.45s, highway life isn't great. The clutch already occasionally hates me crawling or backing into my weird parking space (I live in a neighborhood with very old houses). Recently took a promotion in another location but haven't moved yet, 200km a day makes the gears even more of a priority. Fuel economy and drivability would be so much better. Thinking 4.88s or 5.13s even, gives me room to grow and I'd prefer effectively having a granny gear 1st to a 6th I never really use. Just torn on the whole m186 front situation, do I even spend money on it? Decisions need to be made...
Thats why i ended up going with axle swap. took a little hit on the pocket book but with 33's and 4.10s im running 22mpg on the hwy believe thats roughly 9.3L km/L that's way up from 3.45's and 33's which was 16-18mpg or 6.8-7.4 KM/L even see higher at 65 mph on flat is up in the high 20's.

plus for roughly 6 k got bigger axles. better gears. and dual lockers. and i can run up to a 37" tire with these axles if i truss them
 

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@Bekser

I just put in 4.88's on my 2 door Jeep with 6 speed. I also have a 2.5" lift and 35's.

I'm still driving nicely with no off-roading until I change the gear oil. Trail Jeeps recommended 1000 miles and so that's what I'll do.

Still, I'm already well pleased at the difference. The gears finally "feel right." I have even held steady mph going up hill in 6th. Not a steep hill, but still one I've done many times before and 5th would start to lose speed. WTF??

No heavy acceleration yet, but it's like the Jeep got an extra 50hp and moves much more easily. Not going to do highway speeds until after the gear oil change, but I expect a bit higher rpm's. Not too concerned as it doesn't feel drastic.

HIGHLY recommended IMHO. :beer:

(Can't wait to hit the trail or drive up to Eisenhower Tunnel to really get a feel for the changes.)
 

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man yall dont know sluggish until you try driving rubi 33's with sport 3.45 gears and the 6 speed. Just installed rubi axles with 4.10 my god what a difference. ill be adding 35's in the next year or so when my tires wear out. but will not re-gear. I wouldnt recommend 4.88 with 35's and the 6 speed. with 37's and 4:88's rolling on flat in 6th gear at 2400 rpm your looking closer to 2700 @70 with 35's real world. 4.56 is the number for 35's IMO

https://www.jlwranglerforums.com/fo...3-tires-in-6th-gear-72mph.58253/#post-1257240
One of my good friends with a JK has 4.88 and 35s with anticipation for 37s and it is great. The difference between 4.56 and 4.88 at 70mph is 150rpm (with the 0.72 ratio of 6th for the JL and 35s).
 

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We’ve done nearly every tire/gear combo I can think of. The most common pair that everyone loves is

35s-4.88
37s-5.13
40s-5.38

Auto and 6 speed see little difference in overall performance between the different ratios. There is some but it’s minor overall. The auto has 8 gears to choose from and closer ratios the 6 speed isn’t as lucky which makes it more sensitive to the correct gears

Im more aggressive with gears because the 3.6 is pretty gutless under 2k. The 2.0 “can” go down a bit like 37s with 4.88s due to its torque curve but overall a little extra rpms tend to help

brett
 

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man yall dont know sluggish until you try driving rubi 33's with sport 3.45 gears and the 6 speed. Just installed rubi axles with 4.10 my god what a difference. ill be adding 35's in the next year or so when my tires wear out. but will not re-gear. I wouldnt recommend 4.88 with 35's and the 6 speed. with 37's and 4:88's rolling on flat in 6th gear at 2400 rpm your looking closer to 2700 @70 with 35's real world. 4.56 is the number for 35's IMO

https://www.jlwranglerforums.com/fo...3-tires-in-6th-gear-72mph.58253/#post-1257240
So you're basing this on 0 personal experience? I'm running 5.13s with 37s and I couldn't dream of being higher. If you spend the money for a gear change and only go 4.56s with 35s you're going to regret it. So many people take the gear charts as gospel but forget to take into account the vast difference in rolling mass that happens when going to bigger tires. The factory 6-speed is geared pretty poorly even on the Rubicon, should have come with 4.56s from the factory.
 

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The factory 6-speed is geared pretty poorly even on the Rubicon, should have come with 4.56s from the factory.
I agree and would add that all gas engine Rubicon's (manual or automatic) should be geared with 4.56 from the factory. Based upon my experience with 4.10's and 33's (now 35's), I would be outright lying to say that 4.10 gears are fine with 35's and the transmission compensates for it, because, well, it cannot and does not.
 

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So you're basing this on 0 personal experience? I'm running 5.13s with 37s and I couldn't dream of being higher. If you spend the money for a gear change and only go 4.56s with 35s you're going to regret it. So many people take the gear charts as gospel but forget to take into account the vast difference in rolling mass that happens when going to bigger tires. The factory 6-speed is geared pretty poorly even on the Rubicon, should have come with 4.56s from the factory.
I have quite a bit of gear experience currently running 35’s and 3.73’s on my old pickup... has not problem cruising the freeways and spinning the wheels at any time. It’s not a complicated. It all depends if you daily driving hwy or not. I don’t like spinning 3000 rpm at 70mph. It’s not worth it.
 

word302

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I have quite a bit of gear experience currently running 35’s and 3.73’s on my old pickup... has not problem cruising the freeways and spinning the wheels at any time. It’s not a complicated. It all depends if you daily driving hwy or not. I don’t like spinning 3000 rpm at 70mph. It’s not worth it.
So like I said, 0 experience with either transmission in the JL. Perfect.
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