Gear ratio poll for 37” tires on 17” wheels 3.6 gasser

[Zachanadandy]

I am trying to cognizant of where I can shave impacts to other components given that the 6 pounds gets compounded, when its rotating, by 2 to 10 times depending on the formula used. Not clear on the math with that, but I accept there is some impact.

Also I think some of the stark differences in opinions of how their Gladiators with 37s perform is because of the weight of the tire they chose....its a pretty big range.

My kanati mud hogs are 73lbs each. Just past 22k miles this weekend. Ball joints, tie rod, drag link, control arms, etc are all tight and stock. 37s went on at 1,100 miles. It's been drifted, jumped, and flogged through washboards in the desert at freeway speeds its whole life. I agree that big, heavy tires increase wear but it's not by much in my experience. Our 1st JLUR still had the stock tie rod when stolen at 63k miles. Most of its life on 37s and then 38s. Driven and wheeled hard all over the country. The stock ball joints go 1st, but even they made it to 42k miles. In the replacement 2022 xr they were shot at 32k, but it's on 39s. I also hate KO2s, the worst off road tire I've ever run so there's that.

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[Billkowski]

My kanati mud hogs are 73lbs each. Just past 22k miles this weekend. Ball joints, tie rod, drag link, control arms, etc are all tight and stock. 37s went on at 1,100 miles. It's been drifted, jumped, and flogged through washboards in the desert at freeway speeds its whole life. I agree that big, heavy tires increase wear but it's not by much in my experience. Our 1st JLUR still had the stock tie rod when stolen at 63k miles. Most of its life on 37s and then 38s. Driven and wheeled hard all over the country. The stock ball joints go 1st, but even they made it to 42k miles. In the replacement 2022 xr they were shot at 32k, but it's on 39s. I also hate KO2s, the worst off road tire I've ever run so there's that.

LOL, understood

 

[WILDHOBO]

Looking for consensus on ideal gear ratio for 37” tires. I just installed Mickey Thompson Baja Boss AT with my stock Mojave 4.1 gears. So far seems fine but curious what others have done. My Jeep is a daily driver and off road is fire roads or sand dunes no heavy rock climbing. I’m in Wisconsin so elevation is 700 and not a lot of hills.

With that driving style, I’d do 4.88’s. I tow and rock crawl in the mountains and went with 5.13’s. I couldn’t be happier, on road and off. I still see 8th on the interstate.

 

[Panthers65]

Nobody is arguing against regearing, I'm arguing against gearing so low it ruins freeway driveability. There's no reason to be at 3k rpms downhill with a tailwind with a double overdrive transmission. And anyone arguing you need the extra gearing for rotating mass doesn't understand how low the 1st gear in this 8 speed is. I don't care if you're running stock 4.10s and 40s, it's not like "taking off in 2nd or 3rd gear like someone stated. Every auto in any jeep before this didn't have anywhere near the 1st gear. The late model JKs had the next best transmission... and to match a stock 8 speed with 4.10s they would need 6.32 axle gears. TJs and early JKs would need 7.5-1 axle gears. And yet people ran 35s and 37s on those... with the same 4.88s-5.13s people argue you need with the 8 speed. The fact is you simply don't. Math is math. Even if you think you want to turn 3k rpms at freeway speed downhill, save yourself $3k and downshift. The fact is 7th gear with 4.10s is the same as 8th with 5.13s period. Yes you have more gear multiplication in every gear but the fact is you don't need it and going too deep has its own drawbacks. 4.56s and 37s have been the best combination of the half dozen we've run by far. 5.38s and 38s were the worst, and that's what I get for listening to forum advice from people who think the trans should hold the to gear up hills like it's a 4 speed. Even the most under geared combo we ran of the same 38s and 4.10s was better. 4.56s and 35s felt overgeared on the freeway. 4.10s and 37s work great. Just getting home from another 1200 mile roadtrip in the Mojave. Yes I saw 8th a lot. At 85mph and 2100 rpms like it should be in a double overdrive. 4.56s and 37s was only slightly better and definitely not worth the cost of a regear period. Even 4.56s and 39s in the JLUR are better than being over geared. If you want your Jeep in 8th all the time, jump off the deep end of gears...and watch freeway fuel economy go down. But what do I know, it's not like I have 250k miles on all types of terrains worth of experience with the 8 speed and probably 5 times that in the dozen other Jeeps we owned previously. The double overdrive does hide some of the drawbacks of running deeper gears than you need, but once you're out of shifts, you're out of shifts.

OKay, if you want to do 85 on the interstate I can see where you wouldn't want to gear as deep. however 95% of lifted Jeep Owners have absolutely no desire to do 85MPH all day in their Jeep. I pull a 5K boat with mine, and spend lots of time in the N GA mountains. There is an absolute advantage to having the 5.13's in my truck. I also sold/built Jeeps for 5 years, and can't honestly remember a single person with all the gear swaps we did regret going too deep, but I had a host of customers regret not gearing deep enough.

I made the comment about larger tires starting in 2nd or 3rd gear and it's completely true. To your point, the engineers specifically designed the first gear ratio to be that deep for a reason, it's the benefit of an 8-speed trans vs a 4 or 6 speed. The first gear in the JL/JT transmission is 4.7:1, and the second gear is 3.14:1. A 29" Tall to 37" Tall tire is a 20.69% increase in size, meaning every gear in the transmission is roughly 20% higher. So that deep 4.7 first gear that the engineers determined was needed in the Gladiator is now a 3.7:1. You also end up with 3 (almost 4) overdrive gears vs the 2 that come with the transmission.

by your logic, I'd argue the exact opposite. The Jeep transmission has a 2 OD Gears (7th = .84:1 and 8th = .67:1) and it more than comfortable running deep gear sets. Couple that with the power curve on a 3.6 makes peak HP/Torque on a fairly flat line from around 2800 RPM through 6,000 RPM, there is absolutely no reason to be afraid of your Jeep running 3K. At 85MPH you are drivng a vehicle with the aerodynamics of a brick, there is nothing that will help your MPGs at that speed. For most people with that knowledge, they would rather enjoy the around town/low end torque that comes with a deeper gear set and just understand that they aren't driving a vehicle that will ever be efficient at 85 MPH.

With my 37's and 5.13's I run around 2200 at 65-70MPH and that's more than comfortable for me, Being able to comfortably tow my boat and getting 17 MPG out of a vehicle on 37's is as good as it's going to get for a 6cyl N/A gas engine.

 

[Badweather]

With that driving style, I’d do 4.88’s. I tow and rock crawl in the mountains and went with 5.13’s. I couldn’t be happier, on road and off. I still see 8th on the interstate.

I installed 5.13 gears and could not be happier with the results. I notice all the anti-regear people have not done a regear.

 

[Zachanadandy]

OKay, if you want to do 85 on the interstate I can see where you wouldn't want to gear as deep. however 95% of lifted Jeep Owners have absolutely no desire to do 85MPH all day in their Jeep. I pull a 5K boat with mine, and spend lots of time in the N GA mountains. There is an absolute advantage to having the 5.13's in my truck. I also sold/built Jeeps for 5 years, and can't honestly remember a single person with all the gear swaps we did regret going too deep, but I had a host of customers regret not gearing deep enough.

I made the comment about larger tires starting in 2nd or 3rd gear and it's completely true. To your point, the engineers specifically designed the first gear ratio to be that deep for a reason, it's the benefit of an 8-speed trans vs a 4 or 6 speed. The first gear in the JL/JT transmission is 4.7:1, and the second gear is 3.14:1. A 29" Tall to 37" Tall tire is a 20.69% increase in size, meaning every gear in the transmission is roughly 20% higher. So that deep 4.7 first gear that the engineers determined was needed in the Gladiator is now a 3.7:1. You also end up with 3 (almost 4) overdrive gears vs the 2 that come with the transmission.

by your logic, I'd argue the exact opposite. The Jeep transmission has a 2 OD Gears (7th = .84:1 and 8th = .67:1) and it more than comfortable running deep gear sets. Couple that with the power curve on a 3.6 makes peak HP/Torque on a fairly flat line from around 2800 RPM through 6,000 RPM, there is absolutely no reason to be afraid of your Jeep running 3K. At 85MPH you are drivng a vehicle with the aerodynamics of a brick, there is nothing that will help your MPGs at that speed. For most people with that knowledge, they would rather enjoy the around town/low end torque that comes with a deeper gear set and just understand that they aren't driving a vehicle that will ever be efficient at 85 MPH.

With my 37's and 5.13's I run around 2200 at 65-70MPH and that's more than comfortable for me, Being able to comfortably tow my boat and getting 17 MPG out of a vehicle on 37's is as good as it's going to get for a 6cyl N/A gas engine.

In GA 70mph might work, or west freeway speeds of 80+ are the norm. Nobody ran 7+ to 1 axle gears before the 8 speed because there's no need. The 19 to 1 1st gear ratio with 4.10s (not even factoring in torque converter multiplication before lockup) is more than enough to break the 37s lose if I'm too hard in the throttle at take off. You literally cannot use any more torque than I can. It's rather see 2200rpms at 85mph personally which is why is stock with 4.56s for 37s. At this point I don't feel the need to change out the 4.10s in my mojave though, but it sees those same speeds in the dirt.

 

[Zachanadandy]

I installed 5.13 gears and could not be happier with the results. I notice all the anti-regear people have not done a regear.

Which is why I'm here in every gear thread, the worst gearing/tire combination of the half dozen we've run was the 5.38s and 38s. The same JL was better with 4.10s. Even the 4.56s and 35s felt like the gears were a little low. By far the best combo was 4.56s and 37s. But again I drive faster than most both on and off road.

 

[Greg_L]

It's wild that there is so much partisanship over gearing. LOL.

It's quite clear that humans are broken as a species.

 

[danend]

Running Nitto Recon Grapplers 37X11.5R17LT on my JTR with 4:10s. I was expecting to regear but haven’t felt the need over the last 7 months. I live in Illinois, but have been in the Smoky Mountains as well as some dirt and mud trails. No rock crawling…

I see 8th a lot on the highway.

 

[Badweather]

Never heard anyone say they wished they had not regeared only thing I have heard is that they did not regear enough. Are the stock gears ok, sure they are, the transmission makes a huge difference but once you have done the regear you can feel how much better it drives both on road and off.

 

[Zachanadandy]

Never heard anyone say they wished they had not regeared only thing I have heard is that they did not regear enough. Are the stock gears ok, sure they are, the transmission makes a huge difference but once you have done the regear you can feel how much better it drives both on road and off.

Am I not speaking English? The JLUR on 38s was worse after the regear. Lost 1-2mpg on the freeway. It was actually slower by a half second 0-60 because it had to shift 1 extra time. It was better on the stock 4.10s period. Gearing too deep sucks if you actually drive freeway speeds. Would it have been better with 4.56s or even 4.88s? Absolutely. But over gearing is worse than too tall with this 8 speed. Especially in a Rubicon. With the 4-1 transfer case you've got plenty of crawl ratio with more moderate gearing. There's no advantage in my experience.

 

[WILDHOBO]

I installed 5.13 gears and could not be happier with the results. I notice all the anti-regear people have not done a regear.

Great point. I have yet to hear from anyone saying they regret their regear. Performance ALWAYS increases.

 

[WILDHOBO]

Running Nitto Recon Grapplers 37X11.5R17LT on my JTR with 4:10s. I was expecting to regear but haven’t felt the need over the last 7 months. I live in Illinois, but have been in the Smoky Mountains as well as some dirt and mud trails. No rock crawling…

I see 8th a lot on the highway.

The 11.5 width does help you a lot. You also don’t see the steep grades that mountain owners do. I know they call the Smokey’s “mountains”, but depending on your perspective, they’re more like foothills.

 

[WILDHOBO]

Am I not speaking English? The JLUR on 38s was worse after the regear. Lost 1-2mpg on the freeway. It was actually slower by a half second 0-60 because it had to shift 1 extra time. It was better on the stock 4.10s period. Gearing too deep sucks if you actually drive freeway speeds. Would it have been better with 4.56s or even 4.88s? Absolutely. But over gearing is worse than too tall with this 8 speed. Especially in a Rubicon. With the 4-1 transfer case you've got plenty of crawl ratio with more moderate gearing. There's no advantage in my experience.

You are, but there’s a huge difference between 4.56, 4.88, and even 5.13:1 and 5.38’s. That’s super deep gearing. If I didn’t tow and rock crawl, I’d have gone with 4.88 instead of my 5.13’s to increase mileage.

 

[Wheelin98TJ]

You are, but there’s a huge difference between 4.56, 4.88, and even 5.13:1 and 5.38’s. That’s super deep gearing. If I didn’t tow and rock crawl, I’d have gone with 4.88 instead of my 5.13’s to increase mileage.

Also a huge different between a 3.6 V6 and a 2.0 4 banger turbo.

(He isn't telling you the JLUR he's referring to with 5.38 and 38s is a 4 banger turbo)

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