How long can I run the 3.73 gearing? 8.5x17 Wheels wrapped with BF Goodrich 39x13.50r17 km3s..

[RLOW]

Maybe he came from Facebook. Someone on there posted a thread saying that anything other than Factory sized tires would blow up your whole drivetrain If you don't regear.

Personally I would run factory as long as you can tolerate it, especially if you have a 21 model and haven't experienced the axel seal leak yet. I run 35s in 3.73 and will regear once I'm closer to my warranty expiring.

39s are going to be a dog on 3.73 though.

??? Facebook! Nah! Just being on the safe side.. Honestly, I can't tolerate the ugliness of the stock gladiator. I'm pretty sure it's not just me. I guess I'll be driving a dog for about 6 weeks.. Thanks for the heads up!

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[BLK HOLE]

Probably be ok but I’d def regear asap.

 

[BLK HOLE]

Maybe he came from Facebook. Someone on there posted a thread saying that anything other than Factory sized tires would blow up your whole drivetrain If you don't regear.

Personally I would run factory as long as you can tolerate it, especially if you have a 21 model and haven't experienced the axel seal leak yet. I run 35s in 3.73 and will regear once I'm closer to my warranty expiring.

39s are going to be a dog on 3.73 though.

that’s a lot of driveline load for 39s and 3.73s.

 

[Aonarch]

Stock axles, 3.73s, and 39s?

Oh boy.

 

[RLOW]

that’s a lot of driveline load for 39s and 3.73s.

Stock axles, 3.73s, and 39s?

Oh boy.

Thanks everyone for the input! I've decided to hold off and keep the jt stock until I get the 5.13 gears in. Extreme Terrain.com Eta for the Nitro 5.13 set is January ? Quadratec has the spicer ring & pinion sets and the differential rebuild kit due in by the end of the month. Will that suffice for the regear or do I need the Master ovehaul kit? Inputs please..

 

[BLK HOLE]

Stock axles, 3.73s, and 39s?

Oh boy.

Stock axles can easy roll with 40s without upgrades (besides gears).

 

[Aonarch]

Stock axles can easy roll with 40s without upgrades (besides gears).

Mall Crawler yes, with premature wear included.

 

[TwelveGaugeSage]

As far as what it's going to be like, spend a few days starting your jeep in 2 or 3rd gear instead of first on your factory tires. That's going to be what it's like driving on the 39's with 373s.

I laughed a bit at this. Launching in 2nd gear with 32" tires and his current gearing will still be WAY worse than launching in first gear with 39" tires. For example, at 2000 rpm in 1st gear, he is currently going 10mph in 1st gear and 19mph in second. Go up to 39s and its 12mph and 24mph respectively.

Don't get me wrong, it would be a dog, especially with no throttle controller, but I think it would be livable. That said, I'm SOOOO glad my stock gears are 4.10s even with my little 33s, lol.

 

[DocMike]

I lasted less that a month with 35s and 3.73. This is my opinion. I also live at 6,100 feet.
For me it was a sound investment. I went 4.88 and do not regret it at all.
I'd advise driving a JT with a gear swap to see if you like it.

With 35's and 373's does your Jeep ever get into 8th at highway speeds? I have 373's and am considering moving up to 35's.

 

[JeepOfTheseus]

Thanks everyone for the input! I've decided to hold off and keep the jt stock until I get the 5.13 gears in. Extreme Terrain.com Eta for the Nitro 5.13 set is January ? Quadratec has the spicer ring & pinion sets and the differential rebuild kit due in by the end of the month. Will that suffice for the regear or do I need the Master ovehaul kit? Inputs please..

Purely anecdotal, but I received one of the Spicer 4.88 ring and pinion gear sets from Amazon yesterday, and it arrived with multiple chips on the pinion gear and scratches on the ring gear. I wanted to go with Dana Spicer because...well we have Dana axles. Maybe this was one-off/bad shipping (except the box/packaging was fine), but the quality control was severely lacking.

I have Yukons arriving today, so I'm curious to see if they are any better.

 

[Aonarch]

I laughed a bit at this. Launching in 2nd gear with 32" tires and his current gearing will still be WAY worse than launching in first gear with 39" tires. For example, at 2000 rpm in 1st gear, he is currently going 10mph in 1st gear and 19mph in second. Go up to 39s and its 12mph and 24mph respectively.

Don't get me wrong, it would be a dog, especially with no throttle controller, but I think it would be livable. That said, I'm SOOOO glad my stock gears are 4.10s even with my little 33s, lol.

33 = 4.10
35 = 4.56
37 = 4.88
38> = 5.13

Edit: this is a general list. You can go one step down or one step higher for each tire size, for your preference, fuel economy, accelerate, altitude etc.

Unpopular opinion, the diesel is the same except 33s start at 3.73, then 35s at 4.10s, etc.

 

[TwelveGaugeSage]

33 = 4.10
35 = 4.56
37 = 4.88
38> = 5.13

I think I would prefer

33 = 4.56
35 = 4.88
37+ = 5.13

At 4.10 and 33s, 5th and 6th feel really tall to me.

 

[Ted Striker]

So nobody is gonna say anything anything about running a 39x13.50 tire on a 8.5" wide wheel? I'm surprised a tire shop would even mount that.

 

[Wheelin98TJ]

So nobody is gonna say anything anything about running a 39x13.50 tire on a 8.5" wide wheel? I'm surprised a tire shop would even mount that.

13.50 on an 8.5" wheel is fine.

Tons of people running 12.50 on 8" wide wheels.

8" wide wheel with 12.50 tires, the wheel width is 64% the tire width. 8.5" wheel with 13.50 tires, the wheel width is 63% the tire width.

 

[Ted Striker]

13.50 on an 8.5" wheel is fine.

Tons of people running 12.50 on 8" wide wheels.

8" wide wheel with 12.50 tires, the wheel width is 64% the tire width. 8.5" wheel with 13.50 tires, the wheel width is 63% the tire width.

Yes, other people are doing it, but mainly with 35's or 37's. 39's is a lot of sidewall to put on a width that small.

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