Is anyone running 3.73 gears with 31s and the 42RLE?

Kloper

Kloper

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Currently my Jeep has 3.73 gears and 31s and the 42RLE. I have plans to lift and move to 33s. I've tried the calculator I've seen posted on here quite a few times but I have a hard time getting an actual idea of what the driving experience is like. Is there anyone running with 3.73 gears on 33s with the 42RLE? How is the drive? Sadly my Jeep is 99% daily commuter with highly limited off roading. Should I be saving for a regear or will my current setup work with the planned 33s. I appreciate any opinions, experience, or technical knowledge to help me figure out my build plan.
 
Kloper said:
If not the 3.73 would the next best option be the 4.10 gear set?
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With the 42RLE transmission 4.10 is not even close to enough gear for 33's. The 42RLE's overdrive drops the rpms by 31% which is way too low and much lower than a manual transmission or the 3-speed automatic does. 5.13 may sound crazy but you want nothing higher (ratio-wise) than than 4.88 with 5.13 being ideal for 33" tires. I'm running the 42RLE with 35's and my present 5.38 is, seriously, barely adequate.

And don't be confused by the above "you want nothing higher than 4.88". In ratio-speak, 4.56 is a higher ratio than 4.88 is.

It's all about the 42RLE and few 4x4 shops know enough about the 42RLE to understand why you need 4.88 or (better) 5.13 to turn 33" tires. NO your highway rpms will NOT be too high, they'll barely be high enough. 5.13 is my recommendation.
 
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To give you an idea I have 4.88s with 33s and 42rle. It’s not enough. I am regearing to 5.13s this week because I am putting in lockers anyways. So yes listen to the guys here and not the shop if they fight you on it they don’t know. 5.13s
 
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To make the jump from 3.73 to 5.13 gears I would need to replace my carrier right? I have the Dana 30 front and Dana 35 rear. I remember reading something on the gear breaks here but honestly, this is the first time I've heard anyone even mention 5.13 so I'm a little lost.
 
Don't worry about needing to replace the carriers it's no big deal. And you don't even need to replace them, the "thick" version of the ring gears can be installed which eliminates the need for a replacement carrier. R&P manufacturers like Revolution Gear have them. I'm running 5.38 thick gears now.
 
I have a ‘99 with a 4” lift, 33’s, 5sp & 3.73. It’s ok. I do t remember the last time I saw 5th gear. I never take the TJ in the highway but cruising around town I can tell you I rarely get out of 3rd. At 45/50 MPH I’m barely cresting 3k in 3rd gear. When I’m on a trail I almost never get out of 2nd unless I’m in 4low. No rock crawling, just regular trails.

I have a super 35 kit on the shelf with 4.88 gears waiting for me to get around to it, but until then it’s manageable. Not ideal, but OK for how I use it.
 
qslim said:
I have a ‘99 with a 4” lift, 33’s, 5sp & 3.73. It’s ok. I do t remember the last time I saw 5th gear. I never take the TJ in the highway but cruising around town I can tell you I rarely get out of 3rd. At 45/50 MPH I’m barely cresting 3k in 3rd gear. When I’m on a trail I almost never get out of 2nd unless I’m in 4low. No rock crawling, just regular trails.

I have a super 35 kit on the shelf with 4.88 gears waiting for me to get around to it, but until then it’s manageable. Not ideal, but OK for how I use it.
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Take note, so no one gets confused, those experiences are with a 5-speed manual transmission which is an apples-to-oranges situation when talking about appropriate ratios for the 42RLE automatic transmission.
 
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I've been running 32s and the stock 3.73s for a few months. I thought I'd be fine but it's terrible in Western PA. Jeep goes into the shop for 4.88s and a trutrac next week.
 
Jerry Bransford said:
With the 42RLE transmission 4.10 is not even close to enough gear for 33's. The 42RLE's overdrive drops the rpms by 31% which is way too low and much lower than a manual transmission or the 3-speed automatic does. 5.13 may sound crazy but you want nothing higher (ratio-wise) than than 4.88 with 5.13 being ideal for 33" tires. I'm running the 42RLE with 35's and my present 5.38 is, seriously, barely adequate.

And don't be confused by the above "you want nothing higher than 4.88". In ratio-speak, 4.56 is a higher ratio than 4.88 is.

It's all about the 42RLE and few 4x4 shops know enough about the 42RLE to understand why you need 4.88 or (better) 5.13 to turn 33" tires. NO your highway rpms will NOT be too high, they'll barely be high enough. 5.13 is my recommendation.
Click to expand...
It is easier for some folks to understand that when you are talking about lower gears to use the term- numerically higher.
 
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Kloper said:
Currently my Jeep has 3.73 gears and 31s and the 42RLE. I have plans to lift and move to 33s. I've tried the calculator I've seen posted on here quite a few times but I have a hard time getting an actual idea of what the driving experience is like. Is there anyone running with 3.73 gears on 33s with the 42RLE? How is the drive? Sadly my Jeep is 99% daily commuter with highly limited off roading. Should I be saving for a regear or will my current setup work with the planned 33s. I appreciate any opinions, experience, or technical knowledge to help me figure out my build plan.
Click to expand...
It sucks, I had 3.73 before going to 5.13. I run 70-75 even push 80 on the highway without any issue and my fuel economy got better; RPMs hover around 2600-2800 and the Jeep loves it. I drive my Jeep quite often, you will have no issue with it being a daily driver.
Two of the recommended local "pros" told me I wouldn't be able to drive on the road with 5.13, they had nothing to support their theory, I found another gear installer and he was more than happy to install.
 
How do you tell what type of transmission you have to determine gearing specs? Mine is 2001 Sport 4.0L manual, my build sheet says "3.73 Rear Axle Ratio, Heavy Duty Dana 44 Rear Axle"

I am looking to run 33 x 10.5 R15

I was under the impression I did not need to regear unless I have issues or want more power?
 
rdu-jeep said:
How do you tell what type of transmission you have to determine gearing specs? Mine is 2001 Sport 4.0L manual, my build sheet says "3.73 Rear Axle Ratio, Heavy Duty Dana 44 Rear Axle"

I am looking to run 33 x 10.5 R15

I was under the impression I did not need to regear unless I have issues or want more power?
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Your transmission is the NV3550.
 
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The 42RLE needs to be re-geared from he factory, even on stock size tires.

At least that's what I feel like.
 
Chris said:
The 42RLE needs to be re-geared from he factory, even on stock size tires.

At least that's what I feel like.
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42rle / 29.5" /3.73 = 2052rpm @ 70mph

NV3550/29.5"/3.73 = 2320rpm @ 70mph (nearly 300rpm higher than the 42rle)

AX-15 / 29.5" /3.73 = 2349rpm @ 70mph (nearly 300rpm higher than the 42rle)

NSG370/29.5"/3.73 = 2498rpm @ 70mph (over 400rpm higher than the 42rle)

32rh / 29.5" / 3.73 = 2974rpm @ 70mph (nearly 900rpms higher than the 42rle)
 
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rdu-jeep said:
...
I was under the impression I did not need to regear unless I have issues or want more power?
Click to expand...

Recognizing the loss of power is the hardest part for many to grasp, especially if they bought the Jeep with original gears and larger tires.
 
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