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

[Panthers65]

Oversized tires on a vehicle without regearing is like driving a manual transmission and starting in 2nd or 3rd gear every time instead of 1st. There's a reason old manual trucks that actually tow and are treated like trucks came with a granny gear. Gearing isn't for highway speeds at 80+, then again Jeeps aren't designed to drive 80+. People that actually use their gladiators like trucks and wheel/tow/require low range understand what gearing does.

There is a reason people that have actually driven jeeps with and without gearing and have regeared multiple jeeps in their life understand that Jeeps benefits from overgearing.

And yes, gearing in the tCase is no different than gearing in the axles, if the ratio works out that's great, but the tcase would need to be designed to run 70+. Plenty of off-road built rigs choose to gear tcase/doubler boxes/ect... vs regearing the axles to keep pinion strength. Issue there is the tcase is how deep the gearing is (2.72 or 4.1:1 depending on model), so to make it work your new tires would need to be over 2x the circumference vs the factory tires, most people aren't doubling their tire size and keeping the factory axles so it's not feasible on these types of vehicles.

I had a samurai buggy with a 126:1 final drive on 39's. It was an absolute blast until about 15mph... but it would idle in 1st up a cinder block wall

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[Wheelin98TJ]

Curious idea all around, especially with all the"You gotta regear to be right!" mantra around here, but if you check out some other auto forums, even a physics forum, it would appear regearing really just impacts 1st gear and after that it's just the transmission doing its thing and if you regear to strong it kinda stops doing its thing at 40 cause you're in 8th gear. Love the idea of pursuing magical torque, lol

Axle gearing impacts all gears.

How many times have you heard someone say they don’t see 8th gear? And sometimes not even 7th gear often enough. That’s how you turn an 8 speed into less speeds than 8. Slap big tires on with stock gears.

Mine is stock 3.73 and I have 35s. It’s not ideal at all. The reason I haven’t regeared is because I’m a cheap ass and it’s not my DD.

 

[Zachanadandy]

Do you understand how axle gearing works? Quit bending words to make your argument right.

It's the reality, axle gears×transmission gears=final drive ratio and that is what moves the vehicle down the road. If 5.13s were the right match for 37s with this trans, non-rubicons would come with 4.56 gears... but I'm sure y'all know more than the engineers.

 

[Zachanadandy]

Axle gearing impacts all gears.

How many times have you heard someone say they don’t see 8th gear? And sometimes not even 7th gear often enough. That’s how you turn an 8 speed into less speeds than 8. Slap big tires on with stock gears.

Mine is stock 3.73 and I have 35s. It’s not ideal at all. The reason I haven’t regeared is because I’m a cheap ass and it’s not my DD.

Anyone claiming they don't see 7th is full of it or running 40"+ tires on 3.73s. Sure if you're one of those Jeeps who are convinced they don't handkerchief and can't be driven over 55mph them gear it to the moon, you won't lose anything. If you actually drive it western freeway speeds, going to deep had more negatives than positives. I know. I did it. Even the factory XR with 315s and 4.56s felt like it needed a rather gear in the freeway and was in 8th way too often.

 

[Panthers65]

It's the reality, axle gears×transmission gears=final drive ratio and that is what moves the vehicle down the road. If 5.13s were the right match for 37s with this trans, non-rubicons would come with 4.56 gears... but I'm sure y'all know more than the engineers.

You're ignoring additional rotating mass and the additional weight of the accessories typically put on a lifted Jeep. Plus the Engineers have other factors they have to consider that I don't care about like EPA/mileage ratings.

intended design by the engineers is to appeal to the largest number of potential drivers. Regearing a jeep after lifting and adding larger tires is designed to appeal to the enthusiast. By your logic the entire aftermarket industry shouldn't exist because the "Engineers know what they're doing"....

 

[1550jrit]

While I appreciate the differing opinions on re-gearing versus stock, I can say with 100% certainty that my driving enjoyment is much higher with 5.38’s than it was with 4.10’s and 37’s. I’ve tried hard to consider all of Zach’s reasoning for why I shouldn’t have re-geared, but I’ve never once regretted the decision. My MPG is about the same and I do plenty of 80 mph plus driving, and I must be weird because I never feel like my engine is screaming. In fact, at 80mph I still have about 3800 more rpm to redline. I’m also not bothered by the fact that I’m in 8th by 40mph as the transmission still downshifts when it needs to.. Now that I think of it, I must be super weird because I literally enjoy drive my Jeep everyday without obsessing over 95% of the arguments brought up in this thread by the never re-gear detractors.

These trucks are super drivable with bigger tires and stock gears, no argument there. If you don’t overly obsess over what gear your truck is in for a given speed and have the money to spend on re-gearing, you probably won’t regret the re-gear either We don’t all have to be the same, ‘Merica!

 

[DailyMoparGuy]

After careful consideration of this thread, I will be regearing to 3.45 for my 37s (aspirations of 40s).

Thanks everyone.

 

[Wheelin98TJ]

It's the reality, axle gears×transmission gears=final drive ratio and that is what moves the vehicle down the road. If 5.13s were the right match for 37s with this trans, non-rubicons would come with 4.56 gears... but I'm sure y'all know more than the engineers.

We have talked about this before, maybe in this same thread. You can get a JL from the factory with 4.88 gears and 33” tires. You can practically use any factory gearing option you want to support any argument you want. It’s a moot point.

Anyone claiming they don't see 7th is full of it or running 40"+ tires on 3.73s. Sure if you're one of those Jeeps who are convinced they don't handkerchief and can't be driven over 55mph them gear it to the moon, you won't lose anything. If you actually drive it western freeway speeds, going to deep had more negatives than positives. I know. I did it. Even the factory XR with 315s and 4.56s felt like it needed a rather gear in the freeway and was in 8th way too often.

Who is claiming they don’t see 7th? In my post you quoted I said “And sometimes not even 7th gear often enough”.

If you think an XR needs another gear and is in 8th too often, are you saying you know better than the engineers?

 

[Zachanadandy]

You're ignoring additional rotating mass and the additional weight of the accessories typically put on a lifted Jeep. Plus the Engineers have other factors they have to consider that I don't care about like EPA/mileage ratings.

intended design by the engineers is to appeal to the largest number of potential drivers. Regearing a jeep after lifting and adding larger tires is designed to appeal to the enthusiast. By your logic the entire aftermarket industry shouldn't exist because the "Engineers know what they're doing"....

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.

 

[Zachanadandy]

We have talked about this before, maybe in this same thread. You can get a JL from the factory with 4.88 gears and 33” tires. You can practically use any factory gearing option you want to support any argument you want. It’s a moot point.

Who is claiming they don’t see 7th? In my post you quoted I said “And sometimes not even 7th gear often enough”.

If you think an XR needs another gear and is in 8th too often, are you saying you know better than the engineers?

Because they allow optional gearing custom ordered (for the 55mph top speed, my double overdrive needs to hold the top gear up a cloud crowd) doesn't support your argument in the least. I'd be willing to bet that 90% of the Jeeps ordered that way with the auto are on 37s almost immediately. That is why that factory option exists in my opinion. Even the XR comes with bump stops long enough to run 37s without rubbing, I wonder why....

 

[Greg_L]

4.56s and 37s have been the best combination of the half dozen we've run by far.

That's what my gear ratio math tells me too. For me, 37s and 4.56 gearing gets my Willys back in the equivalent 3.73 range the whole truck is designed around.

But I'm not actually having any complaints about 37s and 3.73s as far as power, shifting, or economy goes, so I'll just roll with it for now.

 

[Zachanadandy]

That's what my gear ratio math tells me too. For me, 37s and 4.56 gearing gets my Willys back in the equivalent 3.73 range the whole truck is designed around.

But I'm not actually having any complaints about 37s and 3.73s as far as power, shifting, or economy goes, so I'll just roll with it for now.

I come off as anti-regear because I listened to the over gear crowd and it sucked. Proper gearing is better, but I find through experience that tall gearing is much more liveable than being too low. You can in fact order a JL or JT on 37s through Jeeps affiliation with AEV...and they come with 4.56 gears.

 

[Billkowski]

I come off as anti-regear because I listened to the over gear crowd and it sucked. Proper gearing is better, but I find through experience that tall gearing is much more liveable than being too low. You can in fact order a JL or JT on 37s through Jeeps affiliation with AEV...and they come with 4.56 gears.

I know I am not going to regear so I am struggling with a decision between the crazy light "37" 12.5 KO2 (65 lbs) and the 37 11.5 Nitto Recon (71 lbs) - which isn't a full 37 either but a bit taller than the KO2. I like the narrower Recon and how it looks but it would seem 6 more pounds is a good chunk of additional rotational weight according to a minor majority of the internet(we dont talk much about tire weight impact on this forum but it is a big deal in some circles). I have a Mojave with Ko2s 315s and it drives great and I want to impact that as little as possible and it seems the KO2s are the way......it's a shame, really like the Recons.

 

[Zachanadandy]

I know I am not going to regear so I am struggling with a decision between the crazy light "37" 12.5 KO2 (65 lbs) and the 37 11.5 Nitto Recon (71 lbs) - which isn't a full 37 either but a bit taller than the KO2. I like the narrower Recon and how it looks but it would seem 6 more pounds is a good chunk of additional rotational weight according to a minor majority of the internet(we dont talk much about tire weight impact on this forum but it is a big deal in some circles). I have a Mojave with Ko2s 315s and it drives great and I want to impact that as little as possible and it seems the KO2s are the way......shame, really like the Recons.

We don't talk about it much here because it's negligible in this application in my opinion. Racing applications it is huge, even carving corners it is very important. You probably aren't doing repeated hard accelerating and braking or trying to carve corners at speed. A 5k pound box on wheels I don't think you'd feel or be able to measure any kind of difference between 2 similar sized tires with a 6lb difference.

 

[Billkowski]

We don't talk about it much here because it's negligible in this application in my opinion. Racing applications it is huge, even carving corners it is very important. You probably aren't doing repeated hard accelerating and braking or trying to carve corners at speed. A 5k pound box on wheels I don't think you'd feel or be able to measure any kind of difference between 2 similar sized tires with a 6lb difference.

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.

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