Rpm's at 80 mph?

Jk909

Jk909

New member
I have a 2014 jk sport with nittos 285/75 r17. Just scheduled an appointment with drew at ORE to put 4.88 gears it it. I currently have the 3.21 gears with auto trans. 5th gear is basically useless. I'm just curious about what your rpm's are when doing 80 on the freeway. Hoping I ordered the right size gears. Thanks fellas!
 
Spudcannons

Spudcannons

New member
Jk909 said:
I have a 2014 jk sport with nittos 285/75 r17. Just scheduled an appointment with drew at ORE to put 4.88 gears it it. I currently have the 3.21 gears with auto trans. 5th gear is basically useless. I'm just curious about what your rpm's are when doing 80 on the freeway. Hoping I ordered the right size gears. Thanks fellas!
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That seems way too deep for 33" tires, I am installing axles with 4.88's for 35" tires. A lot of people here are running 4.88s with 37" tires. my guess would be around 3200 at a minimum maybe more since you would be at 2900 at 70mph.
 
Jk909

Jk909

New member
Spudcannons said:
That seems way too deep for 33" tires, I am installing axles with 4.88's for 35" tires. A lot of people here are running 4.88s with 37" tires. my guess would be around 3200 at a minimum maybe more since you would be at 2900 at 70mph.
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From my understanding they are almost a 35. My buddies 35's measure 33.5x12.5. Mine measure 33x11.5. So only .5 difference in height. Thanks for your help btw
 
jnabird333

jnabird333

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I don't have and haven't been in this combo but I would guess 3100ish.

If you are willing to slow down on the interstate (70), have intentions to move to 35s or 37s, and like to crawl over go fast, I would likely go ahead and only pay for gears once.

If you want to go fast, don't crawl, and are happy with your tire size I wouldn't do more than 4.56s. (You might even consider 4.10s).
 
jnabird333

jnabird333

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Jk909 said:
From my understanding they are almost a 35. My buddies 35's measure 33.5x12.5. Mine measure 33x11.5. So only .5 difference in height. Thanks for your help btw
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That's a fair point... Still I think the gear and that tire size it a bit of a mismatch, unless the compromises are ones you are okay with.
 
Jk909

Jk909

New member
jnabird333 said:
I don't have and haven't been in this combo but I would guess 3100ish.

If you are willing to slow down on the interstate (70), have intentions to move to 35s or 37s, and like to crawl over go fast, I would likely go ahead and only pay for gears once.

If you want to go fast, don't crawl, and are happy with your tire size I wouldn't do more than 4.56s. (You might even consider 4.10s).
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The only reasons why I figured 4.88 is because I pull my boat with it and I will eventually go with a true 35. I guess I'll have to slow down a bit like you said. I went with 285 75's because I was trying to avoid messing with the gears but my jeep is a dog now so I have to do it either way
 
Spudcannons

Spudcannons

New member
Jk909 said:
The only reasons why I figured 4.88 is because I pull my boat with it and I will eventually go with a true 35. I guess I'll have to slow down a bit like you said. I went with 285 75's because I was trying to avoid messing with the gears but my jeep is a dog now so I have to do it either way
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I bet that 4.88s would be great for pulling a boat if you dont mind being slower on the highway or dont do too much highway driving and are going up in tire size definitely go for the 4.88 so you do it once and done.
 
Jk909

Jk909

New member
jnabird333 said:
Great link...

The 3.6L auto has a 0.83 OD ratio in the transmission and use the rolling diameter of your tire (center to road X 2).
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Just did it and it came up with 2800 at 70 and 3200 at 80. I think you are right about maybe going with 4.56
 
jnabird333

jnabird333

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Auto VS Manual transmission make a big difference. My wife has 4.88s in her Jeep with 35s and I have 5.13s in mine with 37s and couldn't be happier with either. They are both manual transmissions though.
 
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