Re-gear?

[LOBBS]

With the auto transmission going from 31.5s to 32.7 tires you wont see a difference in mileage from 3.45s and 4.10s. And minimal performance decrease. The difference is there "mathematically" but the smaller the tire, the more negligible that difference is.

I went from 285 KO2s to 315 KO2s on my Rubicon since they are light. The 17x9 wheels I added were 1 pound heavier than the stock Rubi wheels. So, I was focused on keeping the additional added mass of my upgraded set to an absolute minimum. I still lost a full mpg+ and a noticeable decline in acceleration, braking and just overall driveability in the "best case scenario". I still see 8th on the interstate but a wind gust will cause me to downshift. I can't wait for my Quadratec to finally get my rear gears in (I've had the fronts and install sets for months). I can't even fathom how miserable it would be if I'd gone with some of these insanely heavy wheel and tire combos that a lot do. If you look at what gears are commonly recommended when people do decide to re-gear it could be argued that a Rubicon even with its 4.10s is undergeared on 33s much less 35s or more. But people are generally so excited to get new shoes that they'll convince themselves that sluggish and poor gas mileage is just "a Jeep thing". Or they'd rather spend that ~$2k on some other fancy mod(s) that will get them likes on the 'Gram rather than the one thing that'll improve their quality of life in terms of driveability.

Sponsored

 

[entropy]

I went from 285 KO2s to 315 KO2s on my Rubicon since they are light. The 17x9 wheels I added were 1 pound heavier than the stock Rubi wheels. So, I was focused on keeping the additional added mass of my upgraded set to an absolute minimum. I still lost a full mpg+ and a noticeable decline in acceleration, braking and just overall driveability in the "best case scenario". I still see 8th on the interstate but a wind gust will cause me to downshift. I can't wait for my Quadratec to finally get my rear gears in (I've had the fronts and install sets for months). I can't even fathom how miserable it would be if I'd gone with some of these insanely heavy wheel and tire combos that a lot do. If you look at what gears are commonly recommended when people do decide to re-gear it could be argued that a Rubicon even with its 4.10s is undergeared on 33s much less 35s or more. But people are generally so excited to get new shoes that they'll convince themselves that sluggish and poor gas mileage is just "a Jeep thing". Or they'd rather spend that ~$2k on some other fancy mod(s) that will get them likes on the 'Gram rather than the one thing that'll improve their quality of life in terms of driveability.

Tire size affects MPG and overall performance more than tire weight does regarding gearing. The larger the tire, the more you will notice the difference. Once you go 35s the difference is much worse. Those are also wider than the stock 285s.

I went from the stock 31.5s to "heavy" 33s. My gas mileage is the same of a Rubicon, slightly better on the freeway because high gears (3.45s) would perform better at high speeds than 4.10s. It isn't sluggish at all since the tires are still somewhat small. I see 8th gear all the time, even on a slight incline. The 8speed transmission adjusts and makes up for it on the road. Once you go 35s you wont see 8th gear anymore, so even though the transmission adjusts, it is not using all of its gears in an optimal manner. You have essentially gone to bigger tires with tall gearing and now have a pretty high top speed youre never gonna reach, thats why it isn't optimal. This has nothing to do with weight.

It is a bit more sluggish than the street tires it came with. But I've driven a Rubicon and my Jeep and the difference is negligible. I for once can't tell. I am sure there is one, but it isn't noticeable on the road.

4.10s will give you better acceleration from a stop than 3.45s on 33 inch tires. They might give you close to 1MPG extra in town, but worst highway. It isn't worth the money to go 4.10s and that's why nobody does it. Once you go to a 35 inch tire things start becoming way more noticeable.

If re-gearing it is better to just make the jump to 4.56s. Then you'll start to definitely see a bigger difference than 4.10s. Unless you like to drive fast on the highway.

4.10s are only worth it as an added bonus if installing Rubi axles.

 

[JLUandCJ-7]

Ok, I know this question has been asked in different forms previously but let me ask once more.

I have a JLU sport with 3.45 gears and std tires from the factory. I want to put a set of Rubicon pull-offs on it so say 33”. I do not plan to ever go larger on the tires. I want to maintain the current acceleration and highway behavior and keep reasonable mpg. My use is 9 on road and the other 10% is beach sand and dirt roads. The labor for a gear change in my case is free.

3.6l v6 and auto trans

question: So change to 3.73 or 4.10?

will I need any spacers or suspension change in height to avoid rubbing or better shocks to control the heavier tires?
thank you very much in advance.

P.s. I may tow a boat or overland camping trailer. In my 2007 JKU I have run TrueTrac front and rear with 4.10 and 33s and will likely do that on this one as well. Of course that is a different engine and transmission.

I have 33s with steel all around on my Sahara (3.6 eTorque) with a 3.45 gearing. It performed just fine with stock bumpers and steps, but it got a little slower once I put the armor on. Not enough to make me regear though, although I would welcome it at this point.

I swapped in the tallest Rubicon suspension too.

If I ever step up to 35s, I'll regear or even more likely, do an axle swap.

 

[El Zilcho]

I went from 285 KO2s to 315 KO2s on my Rubicon since they are light. The 17x9 wheels I added were 1 pound heavier than the stock Rubi wheels. So, I was focused on keeping the additional added mass of my upgraded set to an absolute minimum. I still lost a full mpg+ and a noticeable decline in acceleration, braking and just overall driveability in the "best case scenario". I still see 8th on the interstate but a wind gust will cause me to downshift. I can't wait for my Quadratec to finally get my rear gears in (I've had the fronts and install sets for months). I can't even fathom how miserable it would be if I'd gone with some of these insanely heavy wheel and tire combos that a lot do. If you look at what gears are commonly recommended when people do decide to re-gear it could be argued that a Rubicon even with its 4.10s is undergeared on 33s much less 35s or more. But people are generally so excited to get new shoes that they'll convince themselves that sluggish and poor gas mileage is just "a Jeep thing". Or they'd rather spend that ~$2k on some other fancy mod(s) that will get them likes on the 'Gram rather than the one thing that'll improve their quality of life in terms of driveability.

I did the same with my 2L but with slightly heavier wheels. I would agree with about 1mpg lost, but my shifting did not change. I see 8 all the time and it only downshifts on noticeable uphill. Did you reprogram your tire size?

 

[LOBBS]

I did the same with my 2L but with slightly heavier wheels. I would agree with about 1mpg lost, but my shifting did not change. I see 8 all the time and it only downshifts on noticeable uphill. Did you reprogram your tire size?

I did reprogram for the tire diameter, yes.

 

[No IFS]

Don’t waste any money on 3.73. Minimum 4.10. Pick up some Lightly used Rubicon gears they’re everywhere. And reasonably priced. Maybe even look for a pair of takeoff axles with 4.10s. I’ve seen them pretty cheap as well.

 

[Mocopo]

My guess is the 3.45 gears will do fine on 33s.

Like others have said: drive it first.

TIP - enable the automatic transmission gear display on your EVIC. This will help you evaluate how your transmission is behaving with that setup. If you don’t see 8th gear popping up much, that’s a sign that you should consider regearing.



Good luck.

Just changed that setting. It was killing me not seeing what gear I was in, thanks!

 

[Steph1]

Tried exactly what you're about to do and as much as I am a firm re-gearing believer (now more than ever), I can tell you that Rubicon take-offs are a light tire mounted on a light wheel. A 3.6 with auto tranny can handle that set-up very comfortably. So at this point, you have zero need to re-gear, but you do have to dial-in the new tire size in order to get proper rpm transmission shift points.

The problem is from there on up. I saw a total transformation of my Jeep's behavior moving from 285/70R17 to 305/70R17, where the weight of the tires were totally obvious and the drive frustrating as the transmission kept hunting for the right gear and downshifted constantly on the highway. It is then that I decided to get a re-gear, and while doing so, I went up to the tire size I really wanted, which are 315/70R17. Now I am running 4.56 gears and wouldn't look back.

 

[entropy]

Don’t waste any money on 3.73. Minimum 4.10. Pick up some Lightly used Rubicon gears they’re everywhere. And reasonably priced. Maybe even look for a pair of takeoff axles with 4.10s. I’ve seen them pretty cheap as well.

Where have you seen Rubi axles? I saw a pair at Arizona selling for 3k. But usually they sell at around 5k, which is about the same as new.

 

[CarbonSteel]

If you look at what gears are commonly recommended when people do decide to re-gear it could be argued that a Rubicon even with its 4.10s is undergeared on 33s much less 35s or more.

With a 3.6L it absolutely is--especially if you have other heavy mods, tow, or explore higher elevations.

33" = 4.56
35" = 4.88
37" = 5.13
38"+ = 5.38

 

[Xorak]

Tried exactly what you're about to do and as much as I am a firm re-gearing believer (now more than ever), I can tell you that Rubicon take-offs are a light tire mounted on a light wheel. A 3.6 with auto tranny can handle that set-up very comfortably. So at this point, you have zero need to re-gear, but you do have to dial-in the new tire size in order to get proper rpm transmission shift points.

The problem is from there on up. I saw a total transformation of my Jeep's behavior moving from 285/70R17 to 305/70R17, where the weight of the tires were totally obvious and the drive frustrating as the transmission kept hunting for the right gear and downshifted constantly on the highway. It is then that I decided to get a re-gear, and while doing so, I went up to the tire size I really wanted, which are 315/70R17. Now I am running 4.56 gears and wouldn't look back.

I will +1 this comment. When I put Rubi takeoffs on my Sport, it drove exactly like it did with stock tires. I corrected the tire size with a Tazer. I also had a JT Rubicon at the time with 4.10 gears and around town I really couldn't tell a difference between the two.

When I went to 35x12.50s though, I completely lost 8th gear on the interstate. I am planning to upgrade it to 4.56 gears in the future and anticipate it will again drive like stock on the highway. Around town (90% of this Jeeps driving) it's still ok on the 3.45s so it hasn't been a huge priority to upgrade gears yet.

 

[entropy]

With a 3.6L it absolutely is--especially if you have other heavy mods, tow, or explore higher elevations.

33" = 4.56
35" = 4.88
37" = 5.13
38"+ = 5.38

I tow with a 2 door and have no issues on really steep inclines keeping speed with the 3.6..... in fact the 3.6 is better at towing than the 2.0. There is an article somewhere by Jeep engineers where they explain why the 3.6 is the best for towing. Small trailer though so that probably has to do with it since 2doors are limited by their wheelbase to tow up to 2,000lbs. Last trip I loaded my trailer all the way up to 1,700lbs. 0 issues keeping 70~75 on the freeway, passing slower cars and maintaining speed going up the mountain. A 4 door towing close to 3500lbs then yeah I can see how the re-gearing would be necessary.

33'' tires, 3.45 gears.

I off-road on high elevations too with my Jeep. Absolutely 0 issues. I got plenty of torque. uphill, rocks. whatever. Would 4.56 be better? hell yeah. Do I need them? not really. Will I get 4.56s? yes I will lol. But I am going up to true 34s. Otherwise I wouldn't.

 

[Shibadog]

2dr S with Rubi take off KO2’s-no real difference performance wise. 2.0 auto. Drive it. Regears will be pricey and will cost you for your use IMHO.

 

[CarbonSteel]

I tow with a 2 door and have no issues on really steep inclines keeping speed with the 3.6..... in fact the 3.6 is better at towing than the 2.0. There is an article somewhere by Jeep engineers where they explain why the 3.6 is the best for towing. Small trailer though so that probably has to do with it since 2doors are limited by their wheelbase to tow up to 2,000lbs. Last trip I loaded my trailer all the way up to 1,700lbs. 0 issues keeping 70~75 on the freeway, passing slower cars and maintaining speed going up the mountain. A 4 door towing close to 3500lbs then yeah I can see how the re-gearing would be necessary.

33'' tires, 3.45 gears.

I off-road on high elevations too with my Jeep. Absolutely 0 issues. I got plenty of torque. uphill, rocks. whatever. Would 4.56 be better? hell yeah. Do I need them? not really. Will I get 4.56s? yes I will lol. But I am going up to true 34s. Otherwise I wouldn't.

I have a 4 door Rubicon with a 3.6L/ZF8 and does not match my experience at all and have posted a number of threads about it and gone through the full gambit of tires and gearing (33, 35, 37 & 4.10, 4.88, 5.13).

At altitude, the 2.0T is light years better than the 3.6L. I lost about 20% of my HP/TQ moving from sea level to 7K ASL, no avoiding it and the 3.6L does not have 20% of anything to spare. The 2.0T would not be impacted (or would be minimally) by this due to the turbocharger.

It all boils down to your tolerance for loss of performance...it appears that mine is pretty low.

 

[Remorseless]

It all boils down to your tolerance for loss of performance...it appears that mine is pretty low.

Yes. This is why I always recommend a "Try it without regearing first" approach. If it's within your tolerances, save the money. If it's not within your tolerances, it's money well spent.

Sponsored