Need Advice on Gear Ratio

[Cornbread]

Hey all, I am wanting to regear in the near future and am a bit unsure of what would be the proper ratio. My 2000 TJ Sport is on 35's with Dana 35/30 and 3.07 gears currently. It has the 3 speed auto transmission. I'm planning to upgrade to the super 35 kit, lsd in the rear and electronic locker up front while I have someone in their for the regear. I got a deal on the 35's I couldn't turn down and love the look, so that's what I'm building around.

I've been running the 35's on 3.07's for almost two years now and it's not that slow surprisingly. I can run 70 down the interstate (and that's without having recalibrated my speedo for the 35's). When I measure my tires they only measure about 34" tall with 25 psi, maybe this is helping some since they are not truly 35" diameter. I think some may recommend 4.56 but I almost think that 4.10's may be plenty. I plan to add a supercharger of some sort eventually so I'm thinking the added power would match perfect with 4.10's. I only want to do this once so if you think I'm off track please say!

Any advice would be greatly appreciated!

 

[Jerry Bransford]

For 35's and your 3-speed automatic, go for 4.56 when you install the Super 35 kit. 4.56 is optimal for that combination, not 4.10 which is optimal for 33's with your setup.

 

[Cornbread]

For 35's and your 3-speed automatic, go for 4.56 when you install the Super 35 kit. 4.56 is optimal for that combination, not 4.10 which is optimal for 33's with your setup.

Okay thanks! Even if I did intstall a charger, you still recommend the 4.56?

 

[Jerry Bransford]

Okay thanks! Even if I did intstall a charger, you still recommend the 4.56?

Once properly geared with 4.56 I doubt you'd feel the supercharger was needed. And with a Super 35 kit, I am not sure that limited slip differentials are available now like they used to be. Besides, a locker is far more useful offroad than a LSD is. An ARB Air Locker for that Super 35 would be a great choice.

 

[Cornbread]

Once properly geared with 4.56 I doubt you'd feel the supercharger was needed. And with a Super 35 kit, I am not sure that limited slip differentials are available now like they used to be. Besides, a locker is far more useful offroad than a LSD is. An ARB Air Locker for that Super 35 would be a great choice.

Okay thanks! Whenever I feel like coughing up some change I'm going with 4.56. Most of our trails are mud, roots, and rocks all mixed together, but definitely not true "rock crawling by any means". Would you recommend an air locker up front as well? Or lsd? I haven't dug real deep into lockers but I figured on going with an electric controlled locker so I don't have to mess with onboard air, would the air locker be more reliable?

 

[Jerry Bransford]

Okay thanks! Whenever I feel like coughing up some change I'm going with 4.56. Most of our trails are mud, roots, and rocks all mixed together, but definitely not true "rock crawling by any means". Would you recommend an air locker up front as well? Or lsd? I haven't dug real deep into lockers but I figured on going with an electric controlled locker so I don't have to mess with onboard air, would the air locker be more reliable?

LSDs are great for the street but they really don't help offroad except on very easy flat trails if they were slick from rain or snow. Air lockers are great front & rear but they're expensive so a less costly approach for the front would be a lunchbox locker. Front lunchbox lockers like an Aussie are inexpensive, easy to install, and 100% well behaved on the street when you're in 2wd. They only engage enough to notice when you shift into 4x4. You don't want to install a lunchbox locker in the rear though, they are notoriously poorly behaved when in the rear axle.

 

[Cornbread]

LSDs are great for the street but they really don't help offroad except on very easy flat trails if they were slick from rain or snow. Air lockers are great front & rear but they're expensive so a less costly approach for the front would be a lunchbox locker. Front lunchbox lockers like an Aussie are inexpensive, easy to install, and 100% well behaved on the street when you're in 2wd. They only engage enough to notice when you shift into 4x4. You don't want to install a lunchbox locker in the rear though, they are notoriously poorly behaved when in the rear axle.

Okay cool, so during snow/ice would the lunchbox give any problems in 2wd? And could you run in 4 Hi say 20 mph on a bad road? I usually drive my GMC Sierra in bad weather but like to go out and play in the Jeep, I wouldn't want a locker that would be dangerous in snow/ice.

 

[Jerry Bransford]

Okay cool, so during snow/ice would the lunchbox give any problems in 2wd? And could you run in 4 Hi say 20 mph on a bad road? I usually drive my GMC Sierra in bad weather but like to go out and play in the Jeep, I wouldn't want a locker that would be dangerous in snow/ice.

As said above, a front lunchbox locker is unnoticeable when you're in 2wd. If you see warnings against their use in the front axle, pay no attention as such warnings are meant for all types of vehicles. They're perfectly well behaved in a Wrangler TJ's front axle when you're in 2wd. You can run any safe speed in 4hi, I just wouldn't drive in 4Hi on an icy road with a front lunchbox locker.

If you would absolutely need 4Hi on icy roads during the winter where you live, a front Truetrac limited slip differential would be a better choice.

 

[Cornbread]

As said above, a front lunchbox locker is unnoticeable when you're in 2wd. If you see warnings against their use in the front axle, pay no attention as such warnings are meant for all types of vehicles. They're perfectly well behaved in a Wrangler TJ's front axle when you're in 2wd. You can run any safe speed in 4hi, I just wouldn't drive in 4Hi on an icy road with a front lunchbox locker.

If you would absolutely need 4Hi on icy roads during the winter where you live, a front Truetrac limited slip differential would be a better choice.

Thanks for the great advice!

 

[Durmam]

For 35's and your 3-speed automatic, go for 4.56 when you install the Super 35 kit. 4.56 is optimal for that combination, not 4.10 which is optimal for 33's with your setup.

Hi Jerry,
I bought a Jeep last month... And I join this forum that same day.
There's a lot of good information, lot of good reading..... this is my first post.

I got myself a 2000 Saharah, with the same setup 6l, Auto, 35tires on 3.07gears ,
the person that was building it told me that the next step was getting new gears, because the speedometer is 16% less that the actual speed. he told me that he was going to get 3.73's.....
He used a "Rule of three" to determine what gear ratio he needed,
3.07 = 30
X = 35
(3.07*35)/30 = 3.58 will get my speedometer correct again, is this correct ?
Am I doing something wrong, am I missing something, because you recommend a 4.56
is for off road ? does it go crazy on the gasoline?

I will be using the Jeep as a daily drive, of course it's a Jeep I have to get it dirty,
So the occasional off-road maybe 80% on the road 20% off Road

Thanks