Need some advice with regearing

[Az-jewel]

Whats the update?! Hows 4.88 on 35s? do you think going to 37s will still be fine on that ratio with the 6 speed? Thats my issue, I only want to re-gear once and I don't want to do 37s right away, but I think eventually I will do that... I have 33s right now, but my next set of tires will be 35s when they wear out, and once the 35s wear out I'll either stick with 35s or go 37s.

I just nicked it up yesterday and I’m in my break in period. Gotta baby it and not exceed 45mph, etc for 500 miles. I won’t really be able to test them for a while, but it’s definitely different! 1st is short, and the rest are much more responsive than the stock gearing was. I put it in gear and (it the gas and it goes! No more lag! Lovely!
I’ll get to highway and off road evaluation in a few weeks and will check in. 6-speed definitely needs it!

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[JtwJL]

I just nicked it up yesterday and I’m in my break in period. Gotta baby it and not exceed 45mph, etc for 500 miles. I won’t really be able to test them for a while, but it’s definitely different! 1st is short, and the rest are much more responsive than the stock gearing was. I put it in gear and (it the gas and it goes! No more lag! Lovely!
I’ll get to highway and off road evaluation in a few weeks and will check in. 6-speed definitely needs it!

Haha fair enough! I'll be awaiting your post... I have been on such a huge debate between 4.56 and 4.88s but now doing more research and looking at possible future build of going to 37s I am inbetween 4.88s and 5.13s... I think I will go 4.88s though.

 

[vavaroutsos]

Haha fair enough! I'll be awaiting your post... I have been on such a huge debate between 4.56 and 4.88s but now doing more research and looking at possible future build of going to 37s I am inbetween 4.88s and 5.13s... I think I will go 4.88s though.

With the 8-speed automatic you can probably get away with 37s and 4.88 gears (torque converter and closer gear ratios compared to manual). With the 6-speed manual I would go with 5.13 gears if I were going to run 37s. That being said, if you know you will eventually go with 37s, just go with the 5.13 gears (at 2500 RPM in 8th you'll be around 72 mph with a typical 35). 8th gear on the auto is 0.67 vs 6th gear on the manual at 0.72, so top gear RPM will be lower on the auto for the same speed.

 

[JtwJL]

With the 8-speed automatic you can probably get away with 37s and 4.88 gears (torque converter and closer gear ratios compared to manual). With the 6-speed manual I would go with 5.13 gears if I were going to run 37s. That being said, if you know you will eventually go with 37s, just go with the 5.13 gears (at 2500 RPM in 8th you'll be around 72 mph with a typical 35). 8th gear on the auto is 0.67 vs 6th gear on the manual at 0.72, so top gear RPM will be lower on the auto for the same speed.

My issue is that I am going 35s first, once they wear down I'll either decide to do 37s or stay with 35s.

 

[rustyshakelford]

I just nicked it up yesterday and I’m in my break in period. Gotta baby it and not exceed 45mph, etc for 500 miles. I won’t really be able to test them for a while, but it’s definitely different! 1st is short, and the rest are much more responsive than the stock gearing was. I put it in gear and (it the gas and it goes! No more lag! Lovely!
I’ll get to highway and off road evaluation in a few weeks and will check in. 6-speed definitely needs it!

I know that’s the recommendations but you don’t do that when you get a brand new Jeep so drive it! Did they disconnect your batteries and then drive it so it gets reset? If you loose your backup camera and ess it wasn’t done. You’re going to love it regeared, really wakes them up and improves drivability

Brett

 

[Az-jewel]

I know that’s the recommendations but you don’t do that when you get a brand new Jeep so drive it! Did they disconnect your batteries and then drive it so it gets reset? If you loose your backup camera and ess it wasn’t done. You’re going to love it regeared, really wakes them up and improves drivability

Brett

Interesting...I lost my ESS, for which I’m grateful! But my backup camera still works. What does that mean? Was something not done correctly? Should I disconnect my battery?
They did the first 3 short drives for me and want me to avoid freeways, hills and longer than 20-30 minute drives so it doesn’t overheat the diff fluid. But you’re right, we don’t baby a new car normally, and don’t change the fluid after 500 miles. I definitely want to take your advice and just go hit some hills and try it out...I’m just not mechanically inclined enough to fix anything I may wreck!!

Haha fair enough! I'll be awaiting your post... I have been on such a huge debate between 4.56 and 4.88s but now doing more research and looking at possible future build of going to 37s I am inbetween 4.88s and 5.13s... I think I will go 4.88s though.

Exactly! I was in the same debate before doing mine. If you have an automatic Rubi do 4.88. If you are sure you’ll go 37’s and don’t do a lot of highway driving then go to 5.13. why go to 35’s in between? Why not just jump ton37’s? Just a thought!
Either way it’ll be nice to get either...

I’m planning to go check out some nice trails. It’s 103 out here so water will be the goal! I’m not gonna push it, but want to get it in 4wd so I can break in the front gears a bit too!

 

[rustyshakelford]

Interesting...I lost my ESS, for which I’m grateful! But my backup camera still works. What does that mean? Was something not done correctly? Should I disconnect my battery?
They did the first 3 short drives for me and want me to avoid freeways, hills and longer than 20-30 minute drives so it doesn’t overheat the diff fluid. But you’re right, we don’t baby a new car normally, and don’t change the fluid after 500 miles. I definitely want to take your advice and just go hit some hills and try it out...I’m just not mechanically inclined enough to fix anything I may wreck!!


Exactly! I was in the same debate before doing mine. If you have an automatic Rubi do 4.88. If you are sure you’ll go 37’s and don’t do a lot of highway driving then go to 5.13. why go to 35’s in between? Why not just jump ton37’s? Just a thought!
Either way it’ll be nice to get either...

I’m planning to go check out some nice trails. It’s 103 out here so water will be the goal! I’m not gonna push it, but want to get it in 4wd so I can break in the front gears a bit too!

Here’s the procedure. Did the shop adjust your gear ratio in the computer? The 6 speed really requires some extra steps everyonce in a while. Might be worth the try, be sure to disconnect both batteries.

You’re not going to hurt anything with driving it!

 

[Az-jewel]

Here’s the procedure. Did the shop adjust your gear ratio in the computer? The 6 speed really requires some extra steps everyonce in a while. Might be worth the try, be sure to disconnect both batteries.

You’re not going to hurt anything with driving it!

thank you so much! You’re the BEST! I just found that other thread and printed off the instructions. Did you do the drive it in 6th portion too, or just the headlights and brake pedal? I’m waiting to hear back if that owner drove it as well, or just stopped at the brake part? I’m going to call the shop on Monday and ask if they adjusted in the computer. I’m guessing not since they didn’t do this part either.
Thanks again!

 

[JtwJL]

Exactly! I was in the same debate before doing mine. If you have an automatic Rubi do 4.88. If you are sure you’ll go 37’s and don’t do a lot of highway driving then go to 5.13. why go to 35’s in between? Why not just jump ton37’s? Just a thought!
Either way it’ll be nice to get either...

I’m planning to go check out some nice trails. It’s 103 out here so water will be the goal! I’m not gonna push it, but want to get it in 4wd so I can break in the front gears a bit too!

Right now as it is my DD I drive probably 20,000-25,000 KM a year on the highway, which is why I don't want to immediately go to 37s, I also like to work my way up instead of going too big and regretting it. My next step is the 2.5" lift kit which will go on whenever it decides to show up, once my 33s wear down I'll go 35s which I definitely will need to regear for. My issue is when I buy another vehicle in a few years time which will become my new DD for highway driving, I might want to go 37s in the Jeep, so basically trying to avoid re gearing twice if I don't need too.

 

[rustyshakelford]

thank you so much! You’re the BEST! I just found that other thread and printed off the instructions. Did you do the drive it in 6th portion too, or just the headlights and brake pedal? I’m waiting to hear back if that owner drove it as well, or just stopped at the brake part? I’m going to call the shop on Monday and ask if they adjusted in the computer. I’m guessing not since they didn’t do this part either.
Thanks again!

I drive them! That’s the fun part!

Brett

 

[mgroeger]

yup 315=35" roughtly what would the rpm be at at 75 with the 6 speed. on 35's with 4.88

6 Speed, 4.88 gears, 37" tires = 2500 RPMs at 75 MPH.
I would say if you run 4.56 gears with 35s you'd be around the same point.

 

[mgroeger]

Hey guys, I need some help here—thanks in advanced and sorry for the long post. Trying to give as much info as I can:
I recently installed the Mopar 2” lift and a set of 315/70/17 KO2’s. The ride and everything is just fine, however highway driving at 70mph and above isn’t very fun.

I have the 8 speed. Most of the time I sit in 6th, occasionally going into 7th. Very rarely do I go into 8th, everything has to be just right as others before have stated. So now I’m looking into regearing because I can’t live with it like that. I have a Sahara with the limited slip rear, so to my understanding I have the Dana 44 and the 30 up front? Anyways, I’ve been doing a ton of research and I can’t find exactly what I’m looking for based on my Jeep. I’ve seen a lot for the 2.0 or the manuals but nothing really for the 8 speed and 3.6

So based on what I’ve found, 4.10’s seem to be just fine according to rubicon owners and others says go for 4.56’s. I need your guy’s help to make up my mind because I want to do it right the first time. This is my DD and I do a lot of highway type speed, I go off-road about 1-2 times a month but don’t do anything crazy like rock crawling. Main things I’m looking for is getting my 7th and 8th gear back like normal, and better mpg. Cruising 65 I average around 16 mpg, 70 around 14.5-15mpg. I’d like to at least get 1-2mpg back and comfortably drive those speeds like before without feeling like my Jeep is being overworked.

So what’s the consensus? 4.10 or 4.56? I see Yukon sells 4.11 or 4.56 for my axles so I’m assuming the 4.11’s would be slightly better than the 4.10’s? Or am I looking at this wrong all together lol

Again sorry for the long post and I appreciate any help you guys can give me, I have completely no idea when it comes to this type of stuff. Thanks again, Nathan

I'd stick with Dana brand gears and run 4.56. Doing the math for 37" tires puts you at 4.60 which you then round up to 4.88. Based on that I'd use 4.88 for 37s and 4.56 for 35s. I'm sure I'll stir stuff up with that statement because a lot of people run 5.13s for 37s and would recommend 4.88s for 35s. I'm just not one of them.

 

[Az-jewel]

Here’s the procedure. Did the shop adjust your gear ratio in the computer? The 6 speed really requires some extra steps everyonce in a while. Might be worth the try, be sure to disconnect both batteries.

You’re not going to hurt anything with driving it!

Quick question...is this little gear ratio adjustment specific just to manual transmissions?

 

[mgroeger]

Quick question...is this little gear ratio adjustment specific just to manual transmissions?

Not quite sure what that is but it's not regarding re-gearing. The only way to tell the computer you have new gears in your axle is with a Tazer, Superchips or the like. Looks like that is regarding some sensor that is expecting certain parameters at certain speeds for 6th gear.
Re-gearing runs you about $2k and it's just another little smack in the face when you get to drop another $200 just for a Tazer Lite to program the computer with the new gears. It would be nice for that to be an option in some set up menu on the Jeep but we all know that ain't happening.

 

[vavaroutsos]

I'd stick with Dana brand gears and run 4.56. Doing the math for 37" tires puts you at 4.60 which you then round up to 4.88. Based on that I'd use 4.88 for 37s and 4.56 for 35s. I'm sure I'll stir stuff up with that statement because a lot of people run 5.13s for 37s and would recommend 4.88s for 35s. I'm just not one of them.

You are not taking into account the additional weight of the larger tires, and likely heavier wheels. This is rotational mass and takes significant power to accelerate it. Think about how much energy is stored in a large, heavy rotational mass (like a flywheel). Accelerating it isn't for free. This is why light wheels make the most difference on a bicycle.

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