What gear ratio should I install in my Jeep Wrangler TJ / LJ? (and other re-gearing FAQs)
- Thread starter Chris
- Start date
Are you going to answer my question? What do you know that the engineers at Jeep don't?
Yes I have driven many Jeeps in my life time. No I do not like automatic Jeeps or mustangs really! But that’s just my preference and not a knock on you personally. Why are folks so sensitive on this forum. I thought this forum was a discussion about Jeeps. You guys get your feelings hurt too quickly. It’s all good bro! I’m just challenging thought for a healthy discussion and perhaps some clarification, that’s all.
It is a place for discussion about Jeeps, but you aren’t discussing.
And again, regardless of how many you have driven, have you driven a TJ Unlimited on 35's with the factory 4:10 gearing and the auto?
If you had just answered the question 20 posts ago you’d probably have heard the point by now.
I’d run 488’s or 513’s with the 6-speed and 35’s any day. I currently run 456’s with 35’s.
you are way off the mark
discussion requires answering questions that are posed
The 42rle needs a deep gear (5.38 for 35" tires) due to it's .69 overdrive ratio. 5.13s and 35" tires work great in the NSG370 and NV3550.
No, my point is and was if you have not driven one set up like that then you do not know what the fuck you are talking about. And, you still have not answered the question- What do you know that the engineers at Jeep don't?
deadbeat son
TJ Addict
My 4.0/manual transmission equipped TJ runs about 3k rpm at 75mph with 4.56s and 31s. I can't imagine trying to drive it on the highway with these gears and 35s.
From the factory bone stock, the 01 TJ with the 32RH runs 68mph at 3000 rpm.
Wanted to share couple of thoughts here with fellow Jeepers.
I came to conclusion that my 42RLE is not a curse (at least for a guy like me, that plans to run 30.5 real size tires - officially 31.5''), as I initially thought. The issue is that it becomes a blessing, the moment that it is geared correctly. The 0.69 OD allows a very deep gearing, which enables higher RPM for any given speed.
I will try to explain why:
If i compare 32RH and 42RLE, for same tire size (30.5 real size, measured) (assume np231):
32RH with 3.73 gears - 2876RPM at 70PMH, and ratio to the wheels in Low - the first speed (2.74) x NP321 ratio (2.72) x Diff ratio 3.73 = ~27.79
42RLE with 5.38 gears - 2863RPM at 70MPH, and ratio to the wheels in Low - the first speed (2.84) X NP321 ratio (2.72) x Diff ratio 5.38 = ~41.55
Also, 42RLE with 5.38 will get me much-much better acceleration that i have now (3.73 with 42RLE, 4.0 and 30.5 (real measured) tires, because at any given speed the engine will be turning in higher RPM (and as a result generating more torque), compared to 32RH.
The problem is that: I have already bought replacement axles (i have stock Dana 35 and Dana 30 axles) with 4.56 (Dana 44, Ected AUBURN e-locker and Dana30HP with Grizzly and Chromoly shafts), and anyway it is impossible to gear down the Dana 30 to 5.38.
If i would be back in time, before buying my axles, i would spend more money, get Dana 44 front as well, and gear to 5.38. Maybe i would need to install manual hubs to prevent potential vibrations in front driveshaft at highway speeds (manual hubs are great idea anyway, especially given autolocker in front).
I started to get it after mapping the RPM to the torque curve. You can see in the attached curve that anywhere under 2K, the engine does not generate enough torque for proper acceleration, and that it really shines around 3K RPM (close the max torque).
I came to conclusion that my 42RLE is not a curse (at least for a guy like me, that plans to run 30.5 real size tires - officially 31.5''), as I initially thought. The issue is that it becomes a blessing, the moment that it is geared correctly. The 0.69 OD allows a very deep gearing, which enables higher RPM for any given speed.
I will try to explain why:
If i compare 32RH and 42RLE, for same tire size (30.5 real size, measured) (assume np231):
32RH with 3.73 gears - 2876RPM at 70PMH, and ratio to the wheels in Low - the first speed (2.74) x NP321 ratio (2.72) x Diff ratio 3.73 = ~27.79
42RLE with 5.38 gears - 2863RPM at 70MPH, and ratio to the wheels in Low - the first speed (2.84) X NP321 ratio (2.72) x Diff ratio 5.38 = ~41.55
Also, 42RLE with 5.38 will get me much-much better acceleration that i have now (3.73 with 42RLE, 4.0 and 30.5 (real measured) tires, because at any given speed the engine will be turning in higher RPM (and as a result generating more torque), compared to 32RH.
The problem is that: I have already bought replacement axles (i have stock Dana 35 and Dana 30 axles) with 4.56 (Dana 44, Ected AUBURN e-locker and Dana30HP with Grizzly and Chromoly shafts), and anyway it is impossible to gear down the Dana 30 to 5.38.
If i would be back in time, before buying my axles, i would spend more money, get Dana 44 front as well, and gear to 5.38. Maybe i would need to install manual hubs to prevent potential vibrations in front driveshaft at highway speeds (manual hubs are great idea anyway, especially given autolocker in front).
I started to get it after mapping the RPM to the torque curve. You can see in the attached curve that anywhere under 2K, the engine does not generate enough torque for proper acceleration, and that it really shines around 3K RPM (close the max torque).
As a matter of fact, as a person who moved to Texas from a country where gallon of gas costs around 7$ (that was back in Israel), i cannot stop smiling every time i pour gas into my tank.
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