Great deals on TJ parts on Amazon!

Looking for parts for your Jeep Wrangler TJ? Checkout the selection of TJ parts Amazon has to offer, many with 2-day Prime shipping!

Click the image below to browse TJ parts on Amazon.

Jeep Wrangler TJ Parts on Amazon

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.

What gears do I want?

TexasTJ2004

I love my TJ
Supporting Member
Joined
Aug 8, 2021
Messages
347
Location
77380
The issue that needs to take into account that driveshafts are usually balanced up to 3000 RPM (at least this is what I have heard). With 5.13, you will be easily going beyond 3000RPM that driveshafts will see. For example, at 2400 engine RPM ( which you will easily get with 5.13 and 33 inch tires and 4 speed), driveshaft will see something like 3200 rpm all the time.
This means that whatever imperfections you had in pinion angle vs driveshaft, imbalances in driveshaft, especially the front one, are going to hurt you.
 

machoheadgames

LED turn signal club
Supporting Member
Joined
Jan 21, 2021
Messages
1,129
Location
Dallas, TX
The issue that needs to take into account that driveshafts are usually balanced up to 3000 RPM (at least this is what I have heard). With 5.13, you will be easily going beyond 3000RPM that driveshafts will see. For example, at 2400 engine RPM ( which you will easily get with 5.13 and 33 inch tires and 4 speed), driveshaft will see something like 3200 rpm all the time.
This means that whatever imperfections you had in pinion angle vs driveshaft, imbalances in driveshaft, especially the front one, are going to hurt you.

With 33’s you’re going to be beyond that going 70 with any ratio lower than 3.73. And let’s not forget how many others are revving their driveshaft beyond 3000 with no issues, despite what the driveshaft builders recommend.

I have a feeling the factory spins their shafts faster than wood or adams does. My factory truck spins the driveshaft 4000 at 80. Maybe Dana balances them with better equipment. Either way I haven’t had trouble with those types of rpm on the Jeep with a stock, adams double cardan , or custom local built double cardan shaft. I think it’s more of a problem in theory than real world.
 

machoheadgames

LED turn signal club
Supporting Member
Joined
Jan 21, 2021
Messages
1,129
Location
Dallas, TX
The issue that needs to take into account that driveshafts are usually balanced up to 3000 RPM (at least this is what I have heard). With 5.13, you will be easily going beyond 3000RPM that driveshafts will see. For example, at 2400 engine RPM ( which you will easily get with 5.13 and 33 inch tires and 4 speed), driveshaft will see something like 3200 rpm all the time.
This means that whatever imperfections you had in pinion angle vs driveshaft, imbalances in driveshaft, especially the front one, are going to hurt you.

5.13 and 33’s will spin the shaft 3700 at 70. It is what it is. 5.38 will kick that up to 3900. Not really a big difference either way, it’s going to be spinning fast regardless of the ratio chosen unless he just stays stock gearing. So then what?
 
  • Like
Reactions: Jerry Bransford

TexasTJ2004

I love my TJ
Supporting Member
Joined
Aug 8, 2021
Messages
347
Location
77380
5.13 and 33’s will spin the shaft 3700 at 70. It is what it is. 5.38 will kick that up to 3900. Not really a big difference either way, it’s going to be spinning fast regardless of the ratio chosen unless he just stays stock gearing. So then what?

I am not saying not regear. More than that, I believe that the #1 thing that needs to be done to a rig in order to get it to proper driving on highway, is to regear it and to get it to run at proper RPM, like at least 2500 for 31 inch and towards 2750 for 33 inch +.
All I am saying that regearing might expose bunch of issues that needs to be fixed. 5.13 or 5.38 does not matter for this purpose.
When one regears from 3.73, he might get a surprised that his pinion angles were not ideal, his driveshaft sucks or that he might need to switch to manually locking hubs to get proper ride quality because of vibrations. Not saying that all these cannot be fixed, they can be, but they need to be taken into account before deciding on regearing, so that one does not get surprised.
I for example, know that my pinion angles suck both in front and rear. I still didn't install the SYE in the rear. I am currently running 4.56, and getting vibrations from front driveshaft (bad angles and driveshaft has dents). I cannot regear to 5.13 before i fix all this mess. None of these issues caused anything significant when I was running my 3.73 gears.
 
  • Like
Reactions: KcTj

Coletrickle

Member
Supporting Member
Joined
Nov 6, 2021
Messages
30
Location
Illinois
I am not saying not regear. More than that, I believe that the #1 thing that needs to be done to a rig in order to get it to proper driving on highway, is to regear it and to get it to run at proper RPM, like at least 2500 for 31 inch and towards 2750 for 33 inch +.
All I am saying that regearing might expose bunch of issues that needs to be fixed. 5.13 or 5.38 does not matter for this purpose.
When one regears from 3.73, he might get a surprised that his pinion angles were not ideal, his driveshaft sucks or that he might need to switch to manually locking hubs to get proper ride quality because of vibrations. Not saying that all these cannot be fixed, they can be, but they need to be taken into account before deciding on regearing, so that one does not get surprised.
I for example, know that my pinion angles suck both in front and rear. I still didn't install the SYE in the rear. I am currently running 4.56, and getting vibrations from front driveshaft (bad angles and driveshaft has dents). I cannot regear to 5.13 before i fix all this mess. None of these issues caused anything significant when I was running my 3.73 gears.

I have taken all this stuff into consideration. I am willing to accept the problems that may arise from regearing it. I will fix the issues. My hope is that since my Jeep only has 40k miles on it and it has never been bashed around in rocks and such that I may get lucky with only tweaking the driveshaft angle. I dont drive my Jeep on the freeway and it seldom sees speeds over 65mph. I am thinking 5.13 gears is in my future.
 
  • Like
Reactions: TexasTJ2004

machoheadgames

LED turn signal club
Supporting Member
Joined
Jan 21, 2021
Messages
1,129
Location
Dallas, TX
I have taken all this stuff into consideration. I am willing to accept the problems that may arise from regearing it. I will fix the issues. My hope is that since my Jeep only has 40k miles on it and it has never been bashed around in rocks and such that I may get lucky with only tweaking the driveshaft angle. I dont drive my Jeep on the freeway and it seldom sees speeds over 65mph. I am thinking 5.13 gears is in my future.

I would still highly suggest 5.38. Especially if you aren’t going over 65 anyways. If you’re spending that much on regearing, you may as well choose the lowest ratio you can since the lowest will not ruin the Jeep in any capacity. If you had a 3 speed, then sure it makes sense to not just choose the lowest ratio but with the 42RLE and the gear offerings on the market, it’s hard to overgear.

5.38 would be 2530 rpm at 65. That’s still not even as low as the manual guys go (2650 at 65). I wouldn’t worry about 4LO or anything else. The difference in 4LO between 5.13 & 5.38 is a total of 5 feet in a minute at idle. That won’t even be noticeable. The difference between stock 4.10 and 5.38 is 1 mph difference. The slow 4LO is a factor no matter what axle ratio you’ve got, so don’t let that dissuade you.

I would not even give 4.88 any consideration at all. There is nothing ideal about 4.88 with that transmission except maybe on a 30” tire.

For what it’s worth in 4LO:

Speed at Idle:

4.10/32”(33) - 1.53 mph
5.13/32”(33) - 1.23 mph
5.38/32”(33) - 1.17 mph

Feet per minute:

4.10/32”(33) - 135 FPM
5.13/32”(33) - 108 FPM
5.38/32”(33) - 103 FPM

Really splitting hairs here but for the best road performance I’d choose 5.38 hands down.
 
Last edited:
  • Like
Reactions: L J

Mr. Bills

Raconteur Emeritus
Supporting Member
Joined
Nov 24, 2017
Messages
3,981
Location
San Miguel de Allende, Guanajuato, Mexico
. . . 5.38 would be 2530 rpm at 65. . . .

Actually, it won't.

Your calculations do not take into consideration the differences between theoretical or static tire diameter and "effective" tire diameter under load.

See the experiment at this link: https://wranglertjforum.com/threads/tire-size-measurement-methods.38648/page-5#post-641879

In that experiment, which was inspired by observations made by mrblaine and designed to use fixed values to determine "effective" tire diameter for gear calculator purposes, an '06 LJ Rubicon with 5.38 gears and "metric 35" tires ran at 2500 rpm at 66 mph even though Grimm Jeeper gear calculator results are 2379 rpm for that speed. I respectfully submit that based upon those results, it would be impossible for an LJ Rubicon with 42RLE transmission to run at 2530 rpm at 65 mph with smaller "metric 33" tires and the same 5.38 gears. RPMs will be greater than your calculations suggest.

In the real world, with an LJ Rubicon, 42RLE, 5.13 gears, and "metric 33" tires, the owner should see rpms at or near 2600 rpm at 65 mph, which is perfectly acceptable and cannot reasonably be characterized as a poor choice.
 
Last edited:

machoheadgames

LED turn signal club
Supporting Member
Joined
Jan 21, 2021
Messages
1,129
Location
Dallas, TX
Actually, it won't.

Your calculations do not take into consideration the differences between theoretical or static tire diameter and "effective" tire diameter under load.

See the experiment at this link: https://wranglertjforum.com/threads/tire-size-measurement-methods.38648/page-5#post-641879

In that experiment, which was inspired by observations made by mrblaine and designed to use fixed values to determine "effective" tire diameter for gear calculator purposes, an '06 LJ Rubicon with 5.38 gears and "metric 35" tires ran at 2500 rpm at 66 mph even though Grimm Jeeper gear calculator results are 2379 rpm for that speed. I respectfully submit that based upon those results, it would be impossible for an LJ Rubicon with 42RLE transmission to run at 2530 rpm at 65 mph with smaller "metric 33" tires and the same 5.38 gears. RPMs will be greater than your calculations suggest.

In the real world, with an LJ Rubicon, 42RLE, 5.13 gears, and "metric 33" tires, the owner should see rpms at or near 2600 rpm at 65 mph, which is perfectly acceptable and cannot reasonably be characterized as a poor choice.

Thanks, but I know how to measure a tire. height of the hub x2. You're nitpicking. If you go to the gear calculator and play around with the numbers until you figure out where I came up with my rpm, I put in a 32" measurement as an approximation of the real world height of a 33. I've never seen a 33 actually measure 33, they're all around 1" small or more, so I use that as my approximation. It is close enough. I am not with coletrickle and as such am unable to measure his tire to tell him the rpm down to the exact number.

I never said 5.13 would be a poor choice. I said I would choose 5.38 and explained why. I do think the 4LO argument is a poor one, because of the numbers I stated. 5 feet difference of travel at idle in a minute. That is miniscule.

I still think 5.38 is the way to go. No aspect of the driving experience will be ruined by the extra 4.7% of rpm and gearing.
 

Jerry Bransford

TJ Guru Moderator
Staff Member
Supporting Member
Joined
Nov 9, 2015
Messages
24,842
Location
Fleming Island Florida
I agree that 5.38 is the better ratio for 33's when the transmission is the 4-speed 42RLE. In reality, 5.38 is actually barely adequate for my 35's and something even lower would be ideal but 5.38 is as low as the axles can be geared. I have had 5.38 in my TJ with 35's and the 42RLE for several years now and would hate to have mistakenly gone with a higher ratio like 5.13 or 4.88. To me, having the slightly higher 2750 rpms with 33's and 5.38 would be ideal. I loved my 2750 rpms when I was running the AX-15 5-speed manual transmission, 35's, and 4.88 gears.

I wish I had them again with my 42RLE but 5.38 gearing won't give them to me with my 35" tires, it'd take a lower ratio than 5.38.
 
  • Like
Reactions: machoheadgames

rasband

Two Trackbars is Over Rated
Supporting Member
Ride of the Month Winner
Joined
Sep 11, 2018
Messages
8,094
Location
Highlands Ranch, CO
I agree that 5.38 is the better ratio for 33's when the transmission is the 4-speed 42RLE. In reality, 5.38 is actually barely adequate for my 35's and something even lower would be ideal but 5.38 is as low as the axles can be geared. I have had 5.38 in my TJ with 35's and the 42RLE for several years now and would hate to have mistakenly gone with a higher ratio like 5.13 or 4.88. To me, having the slightly higher 2750 rpms with 33's and 5.38 would be ideal. I loved my 2750 rpms when I was running the AX-15 5-speed manual transmission, 35's, and 4.88 gears.

I wish I had them again with my 42RLE but 5.38 gearing won't give them to me with my 35" tires, it'd take a lower ratio than 5.38.

You just need to swap the carrier to go lower, of course you're hitting pretty high velocities with your driveshaft.

https://www.revolutiongear.com/product/dana_44_355_589_ratio_gear_sets
 
  • Like
Reactions: machoheadgames

Jerry Bransford

TJ Guru Moderator
Staff Member
Supporting Member
Joined
Nov 9, 2015
Messages
24,842
Location
Fleming Island Florida
You just need to swap the carrier to go lower, of course you're hitting pretty high velocities with your driveshaft.

https://www.revolutiongear.com/product/dana_44_355_589_ratio_gear_sets
Possible but I'd have to replace my Rubicon lockers. 5.38 is the deepest thick gearset available which is required by the Rubicon locker carriers.

And I could care less about the higher driveshaft rpms. My Tom Wood driveshafts are balanced adequately so that will not be an issue. Neither would it be for any good quality aftermarket driveshaft and even the OEM driveshaft should be fine too. If a driveshaft develops vibrations, take it to a driveshaft shop to have it balanced.
 

Mr. Bills

Raconteur Emeritus
Supporting Member
Joined
Nov 24, 2017
Messages
3,981
Location
San Miguel de Allende, Guanajuato, Mexico
. . . I put in a 32" measurement as an approximation of the real world height of a 33. . . .
. . . I still think 5.38 is the way to go. . . .

With all due respect, if you used 32"as a tire diameter your calculations are still flawed. The effective diameter of a 35" tire on the ground at speed is slightly less than 33". A "metric 33" tire will have an effective diameter at or slightly less than 31".

As for your opinion that any differences in low range between 5.13 and 5.38 with a 4:1 low range are meaningless, ask yourself how much sense it makes when a 5.13 ratio with 4:1 low range and metric 33's is already too low for most easy and moderate four wheeling to choose to go even lower. That's like hitting your thumb with a hammer then hitting it harder to make the pain go away then saying it doesn't really change the experience.

Leave the guy alone. He has tentatively decided on 5.13 gears for his 33" tires, which is an appropriate choice for the 42RLE transmission and NV241OR transfer case for someone who does all around four wheeling rather than technical rock crawling, yet you keep trying to talk him into 5.38's.

Bien Dia.
 

machoheadgames

LED turn signal club
Supporting Member
Joined
Jan 21, 2021
Messages
1,129
Location
Dallas, TX
With all due respect, if you used 32"as a tire diameter your calculations are still flawed. The effective diameter of a 35" tire on the ground at speed is slightly less than 33". A "metric 33" tire will have an effective diameter at or slightly less than 31".

As for your opinion that any differences in low range between 5.13 and 5.38 with a 4:1 low range are meaningless, ask yourself how much sense it makes when a 5.13 ratio with 4:1 low range and metric 33's is already too low for most easy and moderate four wheeling to choose to go even lower. That's like hitting your thumb with a hammer then hitting it harder to make the pain go away then saying it doesn't really change the experience.

Leave the guy alone. He has tentatively decided on 5.13 gears for his 33" tires, which is an appropriate choice for the 42RLE transmission and NV241OR transfer case for someone who does all around four wheeling rather than technical rock crawling, yet you keep trying to talk him into 5.38's.

Bien Dia.

Fuck off.
 
  • Haha
Reactions: L J