What is considered lugging the 4.0?
- Thread starter MrBClark
- Start date
ejay
TJ Addict
With my 04 Rubicon on 33"s and an NV3550 I'm at 2250 RPM on the freeway at 65 MPH in 5th gear. Sea level, level road, verified visually at the gauge and via ODB2 readings. Speed verified by GPS.
No idea if the P.O. re-geared. I'm happy if it's still 4.10 (4.11). Lacks power; yes. Lugging? I don't feel like it but I could just not know what I'm missing.
No idea if the P.O. re-geared. I'm happy if it's still 4.10 (4.11). Lacks power; yes. Lugging? I don't feel like it but I could just not know what I'm missing.
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ejay
TJ Addict
I'm glad someone knows how to use that site. Confuses the heck out of me.
OP
2006TJ1
TJ Enthusiast
It's basically just an Excel sheet. Fill in your trans at the top, tire size (subtracting an inch or so for actual size), and gear ratio.
The important part is at the very bottom. It will spit out an RPM for a given speed in all the gears. This tends to be one of the more useful portions.
OP
Which version of the NV3550 does the TJ come with? Close ratio, wide ratio or HD? And what version of the NP231 does the TJ have? Also, what even is underdrive lol?
OP
What about the T case? The 4:1 option? From what I understand my Jeep does not have underdrive but idk. Thanks
Pull your pumpkin and count the gears. That will tell you for certain what you have. The reason I suggest this is..if you don't know what gears are in there, you also don't know how long they have been swimming in that gear oil. Perfect excuse for changing the oil. You will know when you are lugging by the sound and throttle response, the inline six makes noises that are a good tattletale. Where it is a pathological liar, it can sound like it is revving high at 3-4k rpm. It is perfectly fine there. Open level road, you can go into high gear and let it cruise at low rpm. Let your ears and foot guide you. Don't worry about a healthy and well maintained 4.0, it will take what you throw at it and beg for more.
OP
Yea well the gear oil has been changed twice in the last 6 months lol. Once for a leak near the rear end and once for the axle seal. Had a shop do the axle seal even though I should have done it myself. Lots of $$ for something that can seem simple. Should have had them tell me what gears were in there.
ejay
TJ Addict
On a side note, I read somewhere that 4.56 on 33s basically gives you your 4.10 on 31s back. Don't know how true that is, though.
Airjunky
TJ Enthusiast
The higher number is actually a lower gear. And yes, lower gears are typically better for bigger tires.
2006TJ1
TJ Enthusiast
If you have a Rubicon, it should be the 241 T case. If not, should be a 231. The 4:1 option is in reference to a Tera-Low kit or something along those lines which you probably don't have.
And no, likely no underdrive. This would be something like a RubiCrawler or additional gear reduction box.
I thought my gearing was adequate at 4.10, but not. It seems I should be at least at 4.56 with the 33'' tires.
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You can also use it to determine your actual tire rolling radius. Plug in as exact as possible MPH and RPM with your known gear ratio, and keep changing the tire diameter until they match what you see on the dash.
I've had lots of folks tell me they won't use the calculator because it doesn't match what they have on the dash. Well, that is because you plugged in the wrong tire size. It can't be wrong, it is just simple math.