Lets talk about 37s and 8th gear...

Jkohler

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I believe a set up kit and all is 1032 so right about there.so all just have to decide between 456 or 488.





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islandtees

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I went with 37's Copper Tires. Glad I didn't do 35 as I would have been sorry. The ride is great and don't need to change gearing. I hold 8th without a problem. I am in Fl so pretty much flat.

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Arkewn

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I went with 37's Copper Tires. Glad I didn't do 35 as I would have been sorry. The ride is great and don't need to change gearing. I hold 8th without a problem. I am in Fl so pretty much flat.

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Did you reflash to match your new tire size? I'm curious of those who complain they are loosing 8th gear have done this or are running with factory tire size settings?
 

Jkohler

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I did reset my tire size and checked it against a GPS. It was within 1/2 mph
 

islandtees

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Did you reflash to match your new tire size? I'm curious of those who complain they are loosing 8th gear have done this or are running with factory tire size settings?
Flashing only corrects the speedometer. If you go out of 8th a lot, then you need to change gearing.
 

Brian_18JLUR

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I believe a set up kit and all is 1032 so right about there.so all just have to decide between 456 or 488.

The math for selecting gears is really easy! Take the tire size you want, multiply that by the gear ratio you currently have. Then take that number divided by the original tires that came with the vehicle. This is not 100% perfect, but it's super close and has been working great for all drivers of any vehicle ever made. Having a programmer along with this is nice. The programmer isn't mandatory but very helpful after this math. By changing the gears with this math, it corrects the shift points roughly to a more accurate feel that originally came with your vehicle.


If you want 37s... (36?.. x 4.10 / 32 = 4.68)


4:56 is closest but... if you want more gear, pick up the 4:88s. Both would be fine. Closer to stock is 4:56, more aggressive is going to be 4:88.

So I live in FL where it's flat and hwy driving is very important. I want to run the new KM3 39. The 39 is a true 38.5 without mounting. BFG runs small also..... that will put me at a 38?.... With the math set at 4:86875.... I'll be rounding to 4:88s and killing it. :muscle:

paired with my Tazer I will have zero issues.
 

Jkohler

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I’m more than likely doing 488 even though 456 would get back to where it was.
 

islandtees

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I’m more than likely doing 488 even though 456 would get back to where it was.
4.88 is better but I would go 5.13 Before you argue the point research some forums where knowledgeable jeep people suggest this on the 8 speed. The charts don't take into acct the weight of the tires and wheels is how it was explained to me to get the higher ratios. I run 37's and if I change I will do 5.13
 

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The math for selecting gears is really easy! Take the tire size you want, multiply that by the gear ratio you currently have. Then take that number divided by the original tires that came with the vehicle. This is not 100% perfect, but it's super close and has been working great for all drivers of any vehicle ever made. Having a programmer along with this is nice. The programmer isn't mandatory but very helpful after this math. By changing the gears with this math, it corrects the shift points roughly to a more accurate feel that originally came with your vehicle.


If you want 37s... (36?.. x 4.10 / 32 = 4.68)


4:56 is closest but... if you want more gear, pick up the 4:88s. Both would be fine. Closer to stock is 4:56, more aggressive is going to be 4:88.

So I live in FL where it's flat and hwy driving is very important. I want to run the new KM3 39. The 39 is a true 38.5 without mounting. BFG runs small also..... that will put me at a 38?.... With the math set at 4:86875.... I'll be rounding to 4:88s and killing it. :muscle:

paired with my Tazer I will have zero issues.
I can’t imagine. It’s worth changing from a 4:10 to a 4:56 is worth the time or money.
 

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As to 8th gear. Was the original post wanting to stay in 8th gear? I’d imagine if you’re on a long freeway drive cruising at 70-80 mph. Couldn’t you just slide it over to “manual” and up shift it to 8th and keep it there? You might end up with some low rpm’s but all that’d do is give you a little better gas mileage wouldn’t it? Or am I missing the point of the OP?
 

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As to 8th gear. Was the original post wanting to stay in 8th gear? I’d imagine if you’re on a long freeway drive cruising at 70-80 mph. Couldn’t you just slide it over to “manual” and up shift it to 8th and keep it there? You might end up with some low rpm’s but all that’d do is give you a little better gas mileage wouldn’t it? Or am I missing the point of the OP?
That's a great point!
 

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As to 8th gear. Was the original post wanting to stay in 8th gear? I’d imagine if you’re on a long freeway drive cruising at 70-80 mph. Couldn’t you just slide it over to “manual” and up shift it to 8th and keep it there? You might end up with some low rpm’s but all that’d do is give you a little better gas mileage wouldn’t it? Or am I missing the point of the OP?
It works. And it’s actually got quite a bit of power at 75-80
 

Jkohler

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I've tried the manual shift to 8th. It will not maintain speed unless its down hill or flat as a granite inspection plate. Or maybe it's just my jeep is a wimpy.
 
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As to 8th gear. Was the original post wanting to stay in 8th gear? I’d imagine if you’re on a long freeway drive cruising at 70-80 mph. Couldn’t you just slide it over to “manual” and up shift it to 8th and keep it there? You might end up with some low rpm’s but all that’d do is give you a little better gas mileage wouldn’t it? Or am I missing the point of the OP?
I've read both that it will and it won't stay in 8th when using manual.

I think OnlyOne makes some great points, but playing devil's advocate...he's also using the lightest 37 available in the BFG KO2s. I was debating 37s when I posted this thread and if I had gone that route, it was going to be with KO2s.

I went with 35s in a Falken Wildpeak AT3W and no lift. They're great on and off road. They took me over Engineer Pass last week and 2,000 miles of highway. I stayed in 8th plenty in Texas and Kansas, but the ups and downs of New Mexico and Colorado hardly ever allowed me to visit 8th gear.

Will I want 37s next year? Probably. Will I want 37s if/when I get a lift? Probably. But for now, 35s are plenty.
 

Jkohler

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8th gear is pretty high over drive at .67. I kinda figured it was to good to be true that the JL could handle 37's with no gear change. I believe even a heavier 35 would call for a gear change. To each there own but I'm going to regear mine.
 
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