How big on 3.45 Gears

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Eugene-JLJP

New member
I have the Dynatrac 2” lift and Metalcloak track bars and front upper and lower control arms for my JLU Sport S but now I don’t know what size tires the 3.45 gears can handle. I just have stock rims. So I’m thinking about 285/75 r17 tires. But I’m worried about the gears since I can’t regear right now. Thanks for any help.

Edit: I have the 8speed auto transmission.
 

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Eugene-JLJP

New member
CanadaJeep said:
Auto or Standard? I am running 35's and do not feel the need to regear on an auto.
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I have the 8 speed Auto transmission. My bad. I knew I would leave something out.
That’s good to know with 35’s. I don’t want to loose a lot of the function of the 8AT. I won’t do a lot of highway driving but I don’t want the 8AT to end up a 4 speed lol. I know regearing is probably best but it will take me a long while to save up that money.
 

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Cozdude

Cozdude

Guy with a Red 2-Door
I am running 37’s on mine. You lose 8th gear completely and 7th most of the time. We still cruise down the highway tho and get about 18-20 mpg
 

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Eugene-JLJP

New member
Cozdude said:
I am running 37’s on mine. You lose 8th gear completely and 7th most of the time. We still cruise down the highway tho and get about 18-20 mpg
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It kind of sounds like I might be overthinking things with 285/75r17 size tires. 34’s are a lot smaller than 37’s. Thanks for the info.
 

Jlusahara

Jlusahara

Member
Bynow you most likely went ahead and got the tire you wanted, but I can say that I went from 285/70r17 Rubicon take-offs and replaced the tires with 305/70r17s.

Although I noticed absolutely zero impact with the 285/70s, I must admit that the 305s let their presence known. I did feel that the Jeep was turning a heavier set of tires that are 14lbs more at each corner. I still see 8th gear on the highway, but my average mpg went from 21.5 to 19.5.

I am quite certain that the 1/2 inch difference in the 315 vs the 305 would have had a great impact on both 8th gear useability and mpg.

Therefore, My experience tells me that the 305 is the biggest one can go without a need to regear. Even then, I might consider going from 3.45 to 4.10s, or get a set of 35s and go to 4.56 gears.
 

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Eugene-JLJP

New member
Jlusahara said:
Bynow you most likely went ahead and got the tire you wanted, but I can say that I went from 285/70r17 Rubicon take-offs and replaced the tires with 305/70r17s.

Although I noticed absolutely zero impact with the 285/70s, I must admit that the 305s let their presence known. I did feel that the Jeep was turning a heavier set of tires that are 14lbs more at each corner. I still see 8th gear on the highway, but my average mpg went from 21.5 to 19.5.

I am quite certain that the 1/2 inch difference in the 315 vs the 305 would have had a great impact on both 8th gear useability and mpg.

Therefore, My experience tells me that the 305 is the biggest one can go without a need to regear. Even then, I might consider going from 3.45 to 4.10s, or get a set of 35s and go to 4.56 gears.
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Thanks for the info. I’ve actually been really lazy and haven’t gotten new tires yet. With that info I think I will probably be ok with 285/75 r 17 Toyo Open Country AT3. They seem to be fairly light weight.
 

Jlusahara

Jlusahara

Member
Eugene-JLJP said:
Thanks for the info. I’ve actually been really lazy and haven’t gotten new tires yet. With that info I think I will probably be ok with 285/75 r 17 Toyo Open Country AT3. They seem to be fairly light weight.
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That's the tire I went with, I'd reconsider and go with a 305 which are the same 33.9'' diameter, just 4 lbs more than the 285/75 but look better. the sidebitter tread is more agressive and the tire is an inch wider. But you do you :)
 

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Eugene-JLJP

New member
Jlusahara said:
That's the tire I went with, I'd reconsider and go with a 305 which are the same 33.9'' diameter, just 4 lbs more than the 285/75 but look better. the sidebitter tread is more agressive and the tire is an inch wider. But you do you :)
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Ha!! I love the “but you do you”. I’m stuck with the stock rims for the foreseeable future so width is a concern for me. I didn’t want to go to wide with the +44 offset stock rims. I thought 285 was about as wide as would fit without rubbing things. I didn’t realize the 305 was even a size and I would agree that size probably has a better look.
 

Jlusahara

Jlusahara

Member
LOL...I just meant that I'm totally aware that taste is in nature and my taste ain't no trend setter :). I too run the stock Rubicon wheels and I have zero rubbing. Well, havent been offroading, but so far so good. As said, the sidewall is also more agressive on the 305/70 and the tire doesnt look pinched at all. it is just 1/2 an inch narrower than the recommended width.
 

scoobycarolanNC

scoobycarolanNC

Member
I ran 285/75r18s KM3s on a similar setup (stock rims stock offsets). I bet yuo could get away with 295/70/r17s with no spacers. Nitto has the trail grappler in 35x11.5r17 that'll probably work too but they're DUMB expensive, like $385 a piece.
 

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