It isn't going to happen. I am very certain of this, Heisenberg.
Why is this not also true for 33s? More to the point, why isn't this also true for 33s and the 42rle?
Bolt on long arm kits are a waste of money.
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Will I need to re-gear?
- Thread starter Jacob Mikesh
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It isn't going to happen. I am very certain of this, Heisenberg.
Why is this not also true for 33s? More to the point, why isn't this also true for 33s and the 42rle?
Bolt on long arm kits are a waste of money.
OP
Starrs
TJ Guru
Again.........it’s all a personal opinion. Nobody can tell you what you like better lol. You can’t make somebody like chocolate ice cream if they don’t. Myself and others love 33s with Rubicon gearing...33s and 3.73s might not be bad to some and some might hate them.
Drive it and see what you think. If you dig it, more money in your pocket. It it blows, re-gear. If you need to convince yourself it works, it doesn't.
This is a very much a numbers game. Visit grimmjeeper.com.
Enter your Jeep's stock specs. Transmission, tire size and axle gearing. Then enter your larger tire size. Compare various axle gear ratios. Pay the most attention to your over drive gear.
Your transmission has a very high over drive gear compared to other options. Part of the goal here is to be able to use your OD and not think about it more than you need to. Most people's "fix" if to shut it off.
Understand that your engine's peak power is above 2500rpm and starts dropping off after 3k.
Think about where your would like your rpms to be at highway speeds. This will where to find your preferred ice cream flavor.
FWIW, I put my 75mph at 3k rpm. My normal highway speeds are 65-70mph. This is my daily driver, btw. I like that I can accelerate again in overdrive while on the highway.
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Starrs
TJ Guru
I have stared at the charts way too much lol. You will get a 50/50 split for the regear no regear debate, and there will never be a correct answer to this question because there isn’t one.
The correct answer is always proper gearing. Whether someone chooses to do so is their choice.
Were these charts specific to the transmission? Grimmjeeper is, which is why I recommend it. Every other chart I've seen is pretty generic.
I would like to know how many who have actually regeared are split 50/50.
If the OP does not want to spend the money, then that changes the entire conversation.
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I have a 2004 unlimited with the 3.73's and I just put on 33's with the 2 1/2" OME lift and didn't notice much of a difference in driveability. The 33s are only a 10% increase over the stock 30s. To keep your RPMs the same you would only need to change your 3.73s to 4.10s (a 10% increase). I did go with the BFG KO2 33x1050's since it's a daily driver first and only an occasional off roader. The narrower tires are better on the street and will put less wear on the front end.
So the stock Rubicon with an auto at 60mph runs at 2000ish rpm I know this from driving mine that way. That's 31s and 4.10s, it's a slightly over geared scenario but not badly and allows for lots of pull off the line and reasonable highway preformance. When I went to 35s I put in 5.13 gears that brought me to about 2200 rpm and the preformance was about the same due to the extra tire wight. Now I've gone to 37s and am back to 2000rpm but the jeep is struggling, I really need more gear because of all that extra weight and rolling resistance. A 3.73 ratio may be fine for 30-31" tires but the 33s will have more weight, more rolling resistance, and more wind resistance due to the extra height of your jeep. Those gears will be a dog and you will be killing od every time you get in the jeep. Not to mention the extra heat and slippage in the trans shortening it's life span. I'd strongly advise to decide now what your end goal for tire size with these axles is and regear for that. If you plan on 35s go 5.13 now, if you never plan to go over 33s go 4.88 but I'd recommend away from staying 3.73 as you are already pushing and under geared situation as is.
FYI I generally refer to 60mph because in Canada our highway speed is 100kph so it's a reference I'm used to. I usually don't push to 75 because gas is so expensive here
—
There must have been a time
when we could have said no.
FYI I generally refer to 60mph because in Canada our highway speed is 100kph so it's a reference I'm used to. I usually don't push to 75 because gas is so expensive here
—
There must have been a time
when we could have said no.
How are you making the 10% calculation? If you’re making it based on tire diameter, I.e. a move from 30” to 33” inches, that’s not what is being calculated.
Starrs
TJ Guru
Starrs
TJ Guru
Also not sure how this goes with everybody else’s tires but my 33s and pretty sure everybody else that is running “33s” depending on psi is running 32s maybe 32.5. It’s not that much bigger of a jump so again unless you go to 35s why the need for 4.88 or anything deeper? I get it with 35s, but 33s I will never be convinced a regear is needed.
42rle/29.5"/3.73 = 2052rpm @ 70mph (Arguably undergeared from the factory)
42rle/32.5"/3.73 = 1863rpm @ 70mph
42rle/32.5"/4.10 = 2047rpm @ 70mph (return to factory rpm, still undergeared)
42rle/32.5"/4.56 = 2277rpm @ 70mph (maybe fine for Florida)
42rle/32.5"/4.88 = 2437rpm @ 70mph
42rle/32.5"/5.13 = 2562rpm @ 70mph (acceptable for Colorado)
Compare to the 32rh, AX-15, nv3550 and NSG370 to suggest that the 42rle was undergeared from the factory.
32rh / 29.5" / 3.73 = 2974rpm @ 70mph (nearly 900rpms higher than the 42rle)
AX-15 / 29.5" /3.73 = 2349rpm @ 70mph (nearly 300rpm higher than the 42rle)
NV3550/29.5"/3.73 = 2320rpm @ 70mph (over 300rpm higher than the 42rle)
NSG370/29.5"/3.73 = 2498rpm @ 70mph (over 400rpm higher than the 42rle)
If there is one area of consistency in the complaints for the 42rle, it is that the overdrive is too steep and requires deeper gearing than all the other available TJ transmissions. This is evidence to support that.
42rle/32.5"/3.73 = 1863rpm @ 70mph
42rle/32.5"/4.10 = 2047rpm @ 70mph (return to factory rpm, still undergeared)
42rle/32.5"/4.56 = 2277rpm @ 70mph (maybe fine for Florida)
42rle/32.5"/4.88 = 2437rpm @ 70mph
42rle/32.5"/5.13 = 2562rpm @ 70mph (acceptable for Colorado)
Compare to the 32rh, AX-15, nv3550 and NSG370 to suggest that the 42rle was undergeared from the factory.
32rh / 29.5" / 3.73 = 2974rpm @ 70mph (nearly 900rpms higher than the 42rle)
AX-15 / 29.5" /3.73 = 2349rpm @ 70mph (nearly 300rpm higher than the 42rle)
NV3550/29.5"/3.73 = 2320rpm @ 70mph (over 300rpm higher than the 42rle)
NSG370/29.5"/3.73 = 2498rpm @ 70mph (over 400rpm higher than the 42rle)
If there is one area of consistency in the complaints for the 42rle, it is that the overdrive is too steep and requires deeper gearing than all the other available TJ transmissions. This is evidence to support that.
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Starrs
TJ Guru
I think it is safe to say based on the chart you have provided that factory rubicon gears with 42rle tranny is the same as stock essentially with a “33” that truly measures to 32.5. Is this correct? Just wanna make sure I’m reading this correct.
My 33's only measure about 32" as well. But my 30's were only 29...
The 10% is based on diameter as well as my speedometer. With my speedo at 60 mph on the highway my gps says 66. 10% difference. A 30' tire has a circumference of about 94", a 33' tire is about 104". So every revolution of the tire your travelling 10" farther or again about 10%.
My "chart" is grimmjeeper.
42rle/30.5"/4.10 = 2182rpm @ 70mph
42rle/32.5"/4.10 = 2047rpm @ 70mph
However you want to look at it, compared to all other transmission options, this is still undergeared.