1. #1
    baitcher1's Avatar
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    33" tires with a 3.73 gear ratio

    Is anyone out there running 33"s on an LJ with the stock 3.73 gearing, and if so how much power do you loss compared to running 31" tires?

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    JPNinPA's Avatar
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    I'm running 33 on an 05 unlimited. There is a difference but I'm not sure how to quantify the difference.
    What I could say is on pavement pulling hills in PA was not an issue. Off road wants bad.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

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    Quote Originally Posted by JPNinPA View Post
    I'm running 33 on an 05 unlimited. There is a difference but I'm not sure how to quantify the difference. What I could say is on pavement pulling hills in PA was not an issue. Off road wants bad.
    What transmission do you have?

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    I have the NSG 370 manual six speed
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

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    Quote Originally Posted by JPNinPA View Post
    I have the NSG 370 manual six speed
    I have the 42rle auto with OD. Do you think that will cause a greater loss of power then what your jeep experienced?

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    Re: 33" tires with a 3.73 gear ratio

    I know with 4.10s, the stock was 225/75/16 to a 265/70/17, there was a noticable difference. I have the automatic trans in our 2007.

    225/75-R16 vs 265/70-R17 Tire Comparison - Tire Size Calculator

    This shows the difference in size and which gear would be best
    no more jeeps at this time. next time it will be a cj with a v8

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    Quote Originally Posted by baitcher1 View Post
    I have the 42rle auto with OD. Do you think that will cause a greater loss of power then what your jeep experienced?
    I have the 42rle with 3.73s running 35s. The only thing I do is turn the OD off and have no issues. Granted I know its not a hot rod nor do I have a lead foot off-road.
    US Navy "SPOOK" Retired

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    You will be different from the manual trans due to internal gearing (4th 1:1 vs 1:0.69)and slip from the torque converter.

    TRANSMISSION: 42RLE—AUTOMATIC, FOUR-SPEED OVERDRIVE

    Description
    Electronic governor, electronically controlled converter clutch
    Gear Ratios

    1st.
    2.84
    2nd
    1.57
    3rd
    1
    4th
    0.69
    Axle Ratio
    3.73
    Overall Top Gear
    2.57

    TRANSMISSION: NSG 370 — MANUAL, SIX-SPEED

    Availability
    Std. - All models
    Description
    Six-speed, overdrive, synchronized in all forward gears and reverse, single-rail shift system with top-mounted shift lever
    Clutch
    Hydraulic actuation, dual mass flywheel system
    Gear Ratios

    1st
    4.459
    2nd
    2.614
    3rd
    1.723
    4th
    1
    5th
    0.838
    Reverse
    4.06
    Axle Ratio
    3.73 - 4.0L; 4.11 - Rubicon
    Overall Top Gear
    2.98 - 4.0L; 3.29 - Rubicon

    TRANSFER CASE: NV231 COMMAND-TRAC®
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    Re: 33" tires with a 3.73 gear ratio

    I've got the 42rle with 3.73s and 33s, and I'm happy. I didn't really notice any change when going from 31s to 33s. This is the only TJ I've driven though.

    I did correct the speedo though. Your speedometer will be off, causing your transmission to shift at the wrong points.
    My 2005 Wrangler Build Thread

    “He who is without oil shall throw the first rod.” -Compressions 8.7:1

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    Re: 33" tires with a 3.73 gear ratio

    Quote Originally Posted by tulman22 View Post
    I have the 42rle with 3.73s running 35s. The only thing I do is turn the OD off and have no issues. Granted I know its not a hot rod nor do I have a lead foot off-road.
    I have been wanting to jump up to 33's. How are your rpms in 3rd gear with that set up. How is your gas mileage?

    Sent from my SCH-I535 using Tapatalk

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    Re: 33" tires with a 3.73 gear ratio

    Quote Originally Posted by bowdon_rambler View Post
    I have been wanting to jump up to 33's. How are your rpms in 3rd gear with that set up. How is your gas mileage?

    Sent from my SCH-I535 using Tapatalk
    I've got an 05 Wrangler with the 42RLE and 33s. I cant' comment on the rpms, but I'm pulling about 14.5 mpg - 80% city 20% highway.
    My 2005 Wrangler Build Thread

    “He who is without oil shall throw the first rod.” -Compressions 8.7:1

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    Re: 33" tires with a 3.73 gear ratio

    Quote Originally Posted by TerryMason View Post
    I've got an 05 Wrangler with the 42RLE and 33s. I cant' comment on the rpms, but I'm pulling about 14.5 mpg - 80% city 20% highway.
    Any complaints? Do you still use overdrive most of the time

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    Re: 33" tires with a 3.73 gear ratio

    A point of info on the auto transmissions newer than 85... you only have torque converter slip at low speed, This speed will depend on several things. First is engine size, second is PROGRAMMING. Starting in about 83, Lockup torque converters were becoming standard equipment in EVERY automatic transmission due to EPA Fuel standards Requirements. I had an 84 buick that kept locking and unlocking at 32-34 MPH, BRAND NEW... Had it in to the dealer to take care of this, and transmission guy snuck out of the service bay to hunt me down and talk to me on the sly, told me he couldn't tell me how to do this BUT if you were to go to this one fluid galley in the valve body and open it up one number drill size larger, it wouldn't lock up until the vehicle speed was over 40, and a posted speed of 40 is VERY rare. but they are not allowed to tell customers that. Well you know what I said to do... gas mileage went up, Since the most common speeds not driven on the highway are 25,35, and 45. so there was increased torque at 35 due to the converter doing the work on a small engine, and it had massively improved acceleration below 45... And the 2.8 Loved to do 70-85 on its own to begin with... Any way, All automatics since those days have lockup torque converters due to energy efficiency regulations.
    So bear that in mind when changing tire sizes and gear ratios... they can affect your torque converter... If you are strictly off roading, you may want to check into disconnecting the lock up. or find a way to bypass it at will.

    Edit: Some of the newer (2000 and up) autos have programmable transmissions, so a programmer MAY be a viable investment for some. this is one of the advantages to giving up some fun of driving a stick.
    Last edited by Dragon5126; 07-23-2016 at 06:32 PM.

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    Re: 33" tires with a 3.73 gear ratio

    A point of info on 3.73 gears. In the grand Cherokee Laredo 4.0 the 3.73 was standard equipment. I never had any issues with it towing my Evolution Popup Off Road camper ( 31 inch AT tires 15 inch alloy rims) fully loaded with equipment and sleeps seven including water furnace freezer/refrigerator and stove, shower bathroom and genny are included but outboard. It has electric brakes, but is too big for my 06 TJ 2.4 to handle safely on road, as its over 3K. but the 98 4.0 had no issues with the 3.73 in it. I'm flipping my 5.2 Limited GC to 3.73 for gas mileage reasons, I know for a fact that the gearing in the transmission will handle it as I know others who have done the same, and pull heavier trailers at this ratio, and the every day driving expense is well worth it. The 5.2 has more torque at highway speeds than the 4.0, so I am expecting a drop in overall fuel consumption with this trailer as well. the 5.2 is rolling on 31x9.5x15 Goodrich ATs. The point of this is you need to look at everything when considering a regearing, especially the torque range of your engine. If its all Low end a small change in ratio may not seem like much until you are cruising at highway speeds. Conversely a big change may have you blasting through mud on 40 inchers, at 2000 rpm but it puts your top speed at 40mph at 6000 rpm (yes I'm exaggerating to illustrate a point). So when you do a gear change, Chart it out. compare Your current street speed with the charts that are available before you use them to consider what gears you are going to choose. those charts don't take your engine and transmission ratios into consideration, just the final output, which doesn't always help, when you cant get UP to that speed... remember "Ive Fallen, and dropped my Viagra!"

  15. #15
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    Re: 33" tires with a 3.73 gear ratio

    I went with 32" tires on 2" RE lift and 1.25" wheel spacers. It made a world of difference.





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