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37’s and .410 gears

Gvsukids

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just_another_guy

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Even after changing the tire settings in the computer?
Yes, tire size is dialed in within 1mph gps speed. If there's no wind or a tailwind I can hit 8th sometimes, otherwise I end up in 7th. Towing my boat is usually 4th or 5th.
 

Econn2000

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Absolutely NOT calling your "bluff" here but I wonder how your getting into 8th gear? Does the different x fer case have anything to do with it? (vs a Mojave x fer case) I wonder if it's because the MT tires are very light??? My Mojave doesn't get into 8th unless I do it myself.
I had 37" Yoko MTs on my fairly heavily loaded JTLE, and routinely hit 8th gear on the interstate, but still only averaged 14.5 over the long-term. I recently installed 5:13s which gave me all sorts of performance improvement and improved my mpg to 16.5...however, that requires speeds under 70 mph (around 2100 rpm). I went with 5:13s simply because I do a lot of off-road and pull a small trailer through the mountains. Knowing what I know now, 4:88s would have put me right in the sweet-spot and probably around 18 mpg.
 

RealMcCoy

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I'm running 37" Toyo R/T's with the stock 4.10's and scaled it about 2 weeks ago at 600# over GVWR. I get 14mpg around town and mid 15's on the highway. I will see 8th gear on long flats, downhill or with a tail wind but not many other times.

It's livable...certainly 4.88's would be the way to go.

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Yes but don’t you get tired of the shifting and staying in 7th or 8th gear?
 

HooliganActual

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Yes but don’t you get tired of the shifting and staying in 7th or 8th gear?
I don't really even notice it. I'm not saying that it shouldn't be regeared; but I am saying that my gas mileage is decent for it being a fat pig, I can drive 75 on the highway when I need to, the crawl ratio still works for the trails I go on and if it weren't for the fact that i know it's an 8 speed transmission, I wouldn't miss 8th gear.

I will likely regear at some point because it is the right thing to do and will ultimately make it easier on everything, but when all the chicken littles run around sayin' "your Jeep won't run without a regear on 37's", I just think that it is a little dramatic.

I regeared my Wrangler from 3.73 to 4.56 when I put 35's on it and I couldn't notice a real difference in performance. I'm sure that the tranny, engine, etc. are happier after the regear, but my butt in the seat didn't notice a discernible difference...
 

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Bought mine with 35's and stock 4.10. It ran fine, but 7th was usually where it stayed on the highway. I've now had 37's on it for about a year. Now it usually stays in 6th on the highway until the computer gets happy enough to try 7th, where it will stay until the hint of a hill. 8th is a unicorn. All that said, I really don't notice it unless my ear catches that the engine is running above 3,000, in which case I then manually grab 7th. Otherwise, it runs just fine. I'm not a mpg watcher, so I can't tell you what it gets. My truck is a truck and I use it as such. Range computer bounces between 12's and 13's...but the only time I have ever reset it is the day I bought it 4/2021.

Now, towing my 16' trailer with my tractor on it...that is a different animal. 4th and 5th is where she wants to stay. That puts the RPM way up there unless I manually change it, which then just lugs the hell out of the engine. Mine is my daily. 99% on the road. My work schedule currently limits the fun stuff with my truck. That said, I am definitely going 40's when these 37's are done. The fender chop makes these 37's look tiny :LOL: So, in order to be ready for that, I have already ordered 5.38 gear sets. With my mission of more truck instead of toy, the 5.38's will work perfect with the 40's. I'll be back to normal gear and rpm range.
 

RealMcCoy

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I don't really even notice it. I'm not saying that it shouldn't be regeared; but I am saying that my gas mileage is decent for it being a fat pig, I can drive 75 on the highway when I need to, the crawl ratio still works for the trails I go on and if it weren't for the fact that i know it's an 8 speed transmission, I wouldn't miss 8th gear.

I will likely regear at some point because it is the right thing to do and will ultimately make it easier on everything, but when all the chicken littles run around sayin' "your Jeep won't run without a regear on 37's", I just think that it is a little dramatic.

I regeared my Wrangler from 3.73 to 4.56 when I put 35's on it and I couldn't notice a real difference in performance. I'm sure that the tranny, engine, etc. are happier after the regear, but my butt in the seat didn't notice a discernible difference...
Exactly. That was the exact issue and kick myself for waiting so long to re-gear went to 5:13. Best move imho.
 

troopertrek

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I went from factory 4.10’s on Toyo RT 315/70R17 (rough equivalent of a 35x12.50) to 37x12.50 BFG KO2’s and Dana/Spicer 4.88 gears this past week. The computer has been updated to reflect current parts. It drives similar to stock (4.10 on 33”)… probably a little more pep down low. I got my around town fuel economy back.

I’m seeing just under 1,900RPM @ 60MPH in 8th gear. IMO it was money well spent.


Jeep Gladiator 37’s and .410 gears IMG_6768
 

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Anybody running 37” tires on your stock rubicon with .410 diffs and seeing 8 th gear much?
I have 5:13s and see 8th all the time. It’s so good now. Not a single regret. Pull even the steep hills here in 7th.
 

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Absolutely NOT calling your "bluff" here but I wonder how your getting into 8th gear? Does the different x fer case have anything to do with it? (vs a Mojave x fer case) I wonder if it's because the MT tires are very light??? My Mojave doesn't get into 8th unless I do it myself.
Also have a Mojave, 37” KO2’s, 2” AEV lift and I see 8th as much as I’d expect. Not climbing up hills, always going down a grade from 55-mayyyybe 70.

It’s by no means fast, but I can’t imagine it being better as far as using the available gears.


That said, I probably will go to 4.88 for a little more pep.
 

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Bought mine with 35's and stock 4.10. It ran fine, but 7th was usually where it stayed on the highway. I've now had 37's on it for about a year. Now it usually stays in 6th on the highway until the computer gets happy enough to try 7th, where it will stay until the hint of a hill. 8th is a unicorn. All that said, I really don't notice it unless my ear catches that the engine is running above 3,000, in which case I then manually grab 7th. Otherwise, it runs just fine. I'm not a mpg watcher, so I can't tell you what it gets. My truck is a truck and I use it as such. Range computer bounces between 12's and 13's...but the only time I have ever reset it is the day I bought it 4/2021.

Now, towing my 16' trailer with my tractor on it...that is a different animal. 4th and 5th is where she wants to stay. That puts the RPM way up there unless I manually change it, which then just lugs the hell out of the engine. Mine is my daily. 99% on the road. My work schedule currently limits the fun stuff with my truck. That said, I am definitely going 40's when these 37's are done. The fender chop makes these 37's look tiny :LOL: So, in order to be ready for that, I have already ordered 5.38 gear sets. With my mission of more truck instead of toy, the 5.38's will work perfect with the 40's. I'll be back to normal gear and rpm range.
Thanks for the info. I agree, 8th gear is a unicorn! I am wondering how driveable 40's are for a daily driver????? I mostly drive around town and on trails. I certainly would not expect a 300+ miles on 40's trip to be comfy? I dont know.
 

hobbsserv

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I have a Rubicon with 37 BFG muds. I ran stock 4.10s for a while and upgraded to 4.88. Huge difference. My commute is 30 mins of 70 mph. I stay in 8th were before it was all over 6-7 and 8th downhill. I average 17-17.5 mpg. Love my 4.88s, makes me wonder if 5.13s would have been a better choice.
 

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Your new gear ratio with 37” 36.5 diameter calculated from 33” 32.8 diameter with a 4.10:1 ratio will be 3.62:1
 
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Anybody running 37” tires on your stock rubicon with .410 diffs and seeing 8 th gear much?
I ran that combo for a short time. 4:88s fixed the issue. 37s are too large for 4:10s.
 

Proximo

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Anybody running 37” tires on your stock rubicon with .410 diffs and seeing 8 th gear much?
Oddly enough, I see 8th ALOT more when I'm loaded down with 1200+lbs. Idk why but ...
Jeep Gladiator 37’s and .410 gears 20230619_171908
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