Sponsored

Are you re-gearing for 35s or 37s?

Are you re-gearing for larger tires?


  • Total voters
    459

RUSTYS

Well-Known Member
First Name
Rusty
Joined
Jan 9, 2018
Threads
14
Messages
677
Reaction score
474
Location
PA
Vehicle(s)
JLUR
Occupation
Guitar slinger
The best source of info are Jeep Engineers and lift shops. If you move to 35" tires, they recommend 4.56, if going to 37s at a minimum 4.88, but 5.13 is preferred. The stock gearing - even Rubicon- does NOT ( I repeat NOT) support 35s. If you do not re-gear, the speedo will be off and MPG will take a major hit unless you buy a programmer. Its all about wear and tear so if you plan to keep your Jeep and throw tires on that arent supported, then to do it right, re-gear. If you want to have a better shot at warranty coverage, do the Mopar lift and the Mopar gears (they are now available). More money, but OEM is always better IMO.

To test this theory, I have 35s and the stock 3.45 gears - programmed. My RPMs went higher at speed and my MPH took a 2MPG hit. I re-geared to 4.56 just recently and the MPG climbed, RPMs dropped and I can actually getting into the higher gears on the freeway now. That and my Driveshaft no longer is taking extra stress.

You can ask random people in forums (these are the people here who say, "yea just throw on big tires on stock gears...runs fine" - yikes) or ask experts who either do this for a living / take advice from ones that engineered the JL - I know who I pick.
LMAO!
Sponsored

 

jerseymike

Well-Known Member
First Name
Mike
Joined
Feb 24, 2018
Threads
21
Messages
336
Reaction score
218
Location
Allentown, NJ
Vehicle(s)
2018 Wrangler JL Unlimited Sport S
The best source of info are Jeep Engineers and lift shops. If you move to 35" tires, they recommend 4.56, if going to 37s at a minimum 4.88, but 5.13 is preferred. The stock gearing - even Rubicon- does NOT ( I repeat NOT) support 35s. If you do not re-gear, the speedo will be off and MPG will take a major hit unless you buy a programmer. Its all about wear and tear so if you plan to keep your Jeep and throw tires on that arent supported, then to do it right, re-gear. If you want to have a better shot at warranty coverage, do the Mopar lift and the Mopar gears (they are now available). More money, but OEM is always better IMO.

To test this theory, I have 35s and the stock 3.45 gears - programmed. My RPMs went higher at speed and my MPH took a 2MPG hit. I re-geared to 4.56 just recently and the MPG climbed, RPMs dropped and I can actually getting into the higher gears on the freeway now. That and my Driveshaft no longer is taking extra stress.

You can ask random people in forums (these are the people here who say, "yea just throw on big tires on stock gears...runs fine" - yikes) or ask experts who either do this for a living / take advice from ones that engineered the JL - I know who I pick.

Just out of curiosity, do you have an auto or manual?
 

RUSTYS

Well-Known Member
First Name
Rusty
Joined
Jan 9, 2018
Threads
14
Messages
677
Reaction score
474
Location
PA
Vehicle(s)
JLUR
Occupation
Guitar slinger
Just out of curiosity, do you have an auto or manual?
I don't know what he's running but I can tell you for a fact if you have a Rubicon 6 speed or automatic you can drive it with 35s with stock like performance. He lost me at engineers and lift shops.
 

vavaroutsos

Well-Known Member
First Name
Pete
Joined
Nov 24, 2017
Threads
9
Messages
621
Reaction score
413
Location
Scotts Valley, CA
Vehicle(s)
2015 Sprinter Crew Van 2500 High Roof 144" WB OM651 Brilliant Silver, 2019 JLR 3.6L 6SPD Granite Crystal
I don't know what he's running but I can tell you for a fact if you have a Rubicon 6 speed or automatic you can drive it with 35s with stock like performance. He lost me at engineers and lift shops.
That may be true, but stock performance with the 6 speed isn't great. I would re-gear to 4.88 with a 6 speed and 35" tires.
 

RUSTYS

Well-Known Member
First Name
Rusty
Joined
Jan 9, 2018
Threads
14
Messages
677
Reaction score
474
Location
PA
Vehicle(s)
JLUR
Occupation
Guitar slinger
That may be true, but stock performance with the 6 speed isn't great. I would re-gear to 4.88 with a 6 speed and 35" tires.
Weird. I'm running 38s on my JLUR with an automatic and don't have any real issues. I will be swapping out the 4.10s for 5.13s. I don't know anyone with a Rubicon on 35s with either transmission complaining.
 
  • Like
Reactions: JC7

Sponsored

vavaroutsos

Well-Known Member
First Name
Pete
Joined
Nov 24, 2017
Threads
9
Messages
621
Reaction score
413
Location
Scotts Valley, CA
Vehicle(s)
2015 Sprinter Crew Van 2500 High Roof 144" WB OM651 Brilliant Silver, 2019 JLR 3.6L 6SPD Granite Crystal
Weird. I'm running 38s on my JLUR with an automatic and don't have any real issues. I will be swapping out the 4.10s for 5.13s. I don't know anyone with a Rubicon on 35s with either transmission complaining.
I think the automatic does quite a bit better with 35" tires and 4.10 gears. With 8 gears the ratios are closer together and the torque converter helps off the line. With the manual, the gears are really too far apart (geared more for a diesel if you ask me). In stock form I almost never use 6th gear (about 2000 rpm @ 65 mph) unless I'm on a down hill or have a tail wind. 5th gear is much more usable at normal freeway speeds. Changing from 4.10 to 4.88 gears, and 33" to 35" tires, will make 6th gear pretty equivalent to 5th gear in stock form. I feel this will be better for me as I'll have a really short 1st gear for crawling and I don't drive that fast on the freeway in my Jeep.
 

TxJeepers

Well-Known Member
Joined
Nov 20, 2017
Threads
99
Messages
1,058
Reaction score
1,239
Location
USA
Vehicle(s)
2022 JLUR XR
Just because you can doesn't mean you should... I guess if you are mall crawlz who cares, run 37's on stock gears and let the computer/tranny figure it out right?

I'll be doing 4.88's, maybe 5.13's. TBD. I will start off though running 37's without the re-gear. Waiting in part on more options for diff covers so I don't need to buy diff oil twice and to see if AEV releases a Procal for JL. Sure there are programmer options today, but I've been happy with simplicity of the Procal over the JK years.
 

vavaroutsos

Well-Known Member
First Name
Pete
Joined
Nov 24, 2017
Threads
9
Messages
621
Reaction score
413
Location
Scotts Valley, CA
Vehicle(s)
2015 Sprinter Crew Van 2500 High Roof 144" WB OM651 Brilliant Silver, 2019 JLR 3.6L 6SPD Granite Crystal
Just because you can doesn't mean you should... I guess if you are mall crawlz who cares, run 37's on stock gears and let the computer/tranny figure it out right?

I'll be doing 4.88's, maybe 5.13's. TBD. I will start off though running 37's without the re-gear. Waiting in part on more options for diff covers so I don't need to buy diff oil twice and to see if AEV releases a Procal for JL. Sure there are programmer options today, but I've been happy with simplicity of the Procal over the JK years.
Check out the YouTube videos from Banks Power on diff covers. You might just want to stick with the nodular iron covers from Dana/Spicer after watching them.
 

Kelowna

Active Member
First Name
Tom
Joined
Aug 5, 2018
Threads
0
Messages
33
Reaction score
20
Location
Kelowna Bc
Vehicle(s)
2018 Wrangler JL Sahara Unlimited
Vehicle Showcase
1
I went with the Mopar lift kit and 35". I however am experiencing some noise when the vehicle is in a deceleration down from 25kms to 21kms. Anyone else hearing a rotational clunking noise at that speed with 35's?

IMG_20180718_172339.jpg
 

JMONEZ

Well-Known Member
First Name
Jared
Joined
Nov 29, 2017
Threads
34
Messages
342
Reaction score
208
Location
el dorado hills CA
Vehicle(s)
2019 JLUR
Occupation
Self employed
Vehicle Showcase
1

Sponsored

MojitoJLUR

Well-Known Member
Joined
Jan 11, 2018
Threads
21
Messages
1,454
Reaction score
1,721
Location
Detroit, MI
Vehicle(s)
2018 JLUR Mojito
I'm in the 37s with stock rubicon gears club. I'm not super concerned about the acceleration loss, but I do notice I lost 8th gear and sometimes 7th if going into the wind. I drive 20k miles a year and a lot of highway so that's my first concern with regearing. I'd like to optimize the drive at 75 mph. I go wheeling probably 10 times a year and definitely not rock crawling, but trail raiding and dunes.

I've read so many different opinions that I don't think I could be any more confused lol....(this is also my first jeep so I'm brand new to all this)

I know it's all math, but I haven't figured out where to calculate it at yet. Where can I find out what gears I'd want to make it run basically similar to the stock gears on the stock 33s as now with new gears and 37s?
 

vavaroutsos

Well-Known Member
First Name
Pete
Joined
Nov 24, 2017
Threads
9
Messages
621
Reaction score
413
Location
Scotts Valley, CA
Vehicle(s)
2015 Sprinter Crew Van 2500 High Roof 144" WB OM651 Brilliant Silver, 2019 JLR 3.6L 6SPD Granite Crystal
I'm in the 37s with stock rubicon gears club. I'm not super concerned about the acceleration loss, but I do notice I lost 8th gear and sometimes 7th if going into the wind. I drive 20k miles a year and a lot of highway so that's my first concern with regearing. I'd like to optimize the drive at 75 mph. I go wheeling probably 10 times a year and definitely not rock crawling, but trail raiding and dunes.

I've read so many different opinions that I don't think I could be any more confused lol....(this is also my first jeep so I'm brand new to all this)

I know it's all math, but I haven't figured out where to calculate it at yet. Where can I find out what gears I'd want to make it run basically similar to the stock gears on the stock 33s as now with new gears and 37s?
With the tall 8th gear in the auto I would go with 5.13 gears. That will be a little more RPM than stock at the same speed, but you'll need a bit more torque to account for the additional mass of the larger tires if you want it to feel similar to stock.
 

MojitoJLUR

Well-Known Member
Joined
Jan 11, 2018
Threads
21
Messages
1,454
Reaction score
1,721
Location
Detroit, MI
Vehicle(s)
2018 JLUR Mojito
With the tall 8th gear in the auto I would go with 5.13 gears. That will be a little more RPM than stock at the same speed, but you'll need a bit more torque to account for the additional mass of the larger tires if you want it to feel similar to stock.
What is this based on because earlier someone else claimed 4.56 puts you back to similar to stock?
 

vavaroutsos

Well-Known Member
First Name
Pete
Joined
Nov 24, 2017
Threads
9
Messages
621
Reaction score
413
Location
Scotts Valley, CA
Vehicle(s)
2015 Sprinter Crew Van 2500 High Roof 144" WB OM651 Brilliant Silver, 2019 JLR 3.6L 6SPD Granite Crystal
What is this based on because earlier someone else claimed 4.56 puts you back to similar to stock?
Do you want similar RPM at the same speed, or similar feel in terms of acceleration? 4.56 gears is the closest in terms of RPM (it's slightly less RPM than stock). I think 5.13 would feel more like stock in terms of acceleration as you have much more rotational mass to accelerate with the 37" tires. With 5.13 gears you would be at about 2400 RPM in 8th gear at 75 mph. I definitely wouldn't go less than 4.88. I have a spread sheet I can send you to play with this if you like.
 

MojitoJLUR

Well-Known Member
Joined
Jan 11, 2018
Threads
21
Messages
1,454
Reaction score
1,721
Location
Detroit, MI
Vehicle(s)
2018 JLUR Mojito
Do you want similar RPM at the same speed, or similar feel in terms of acceleration? 4.56 gears is the closest in terms of RPM (it's slightly less RPM than stock). I think 5.13 would feel more like stock in terms of acceleration as you have much more rotational mass to accelerate with the 37" tires. With 5.13 gears you would be at about 2400 RPM in 8th gear at 75 mph. I definitely wouldn't go less than 4.88. I have a spread sheet I can send you to play with this if you like.
That would be much appreciated. To be honest, I'm more concerned with the MPG (I know, I know, its a jeep) and drive at expressway speeds as that is where most of my driving happens. I also want to create as less stress as possible on the other components due to the larger tires. I've been leaning towards 4.88 but I honestly don't have any basis for that except that seems to be a very common answer from others.
Sponsored

 
 



Top