4.88 vs 5.13
10-11-2018, 04:53 AM
#11
JK Jedi
Since you don't have a budget and not sure what to expect. $10,000 is what you should realistically expect to spend to run 37's on a rig that runs good down the road. There is a couple ways to doe it either a low lift with flat fenders with lots of trimming that minimized the amount of suspension and steering you have to address or run a 3"+ lift that basically requires you to replace most of the suspension and steering to correct the geometry with adjustable heavy duty links.
4.88 will be good gearing for you. Lots of threads out there to run 37's and it just depends on how you want to build. A true size 35" tire would be a more sensible build at a lower cost (around $2500) and will get you most places you want to go and will be fine with the stock 4.10 gearing if you have them. The newer rubicons come with either 3.73 or 4.10 gears.
4.88 will be good gearing for you. Lots of threads out there to run 37's and it just depends on how you want to build. A true size 35" tire would be a more sensible build at a lower cost (around $2500) and will get you most places you want to go and will be fine with the stock 4.10 gearing if you have them. The newer rubicons come with either 3.73 or 4.10 gears.
10-12-2018, 08:55 AM
#12
JK Enthusiast
The difference between 4.88's and 5.13's on a 37" (36") tire at 55mph is 100rpm.
Hardly seems a tough call.
Even with 5.38's it's only a 200rpm difference, and you are still running at less than 2200rpm at 55... say you get frisky and drive 10mph over all the way to work... still under 2600rpm.
I ran my 2013 (3.6, 6spd rubi) with 5.13's on 35's(34") for 2 years... for one of those years I was doing 75-80mph for an ~hour straight on my way to work, and home again. cruise rpm was 3000-3200rpm.
Jeep never missed a beat. If I recall, low 18mpg acting like that, and if I held it to 70mph then high 18mpgs... occasional 19mpg if the wind was in my favour...
I recently went to 37's, and, really miss the zip I had with 35's/5.13's... makes me want 5.38's...
So, in my opinion, if you are definitely going to 37's, just go 5.38's and be done with it.
And, as far as the rubi 4:1, with the 6sp, even on 35's with the 5.13's there were times I wanted even lower gearing... so, I'd not be concerned about making teh t-case "too low" or, "useless".
Edit...
Since you asked to have explained advantages of going one way or another, I'll offer my experience/observations, related directly to a standard trans Jeep that is used for commuting and rock crawling.
Higher numerical gear advantages street driving;
minimal clutch slip/throttle (no throttle required) required when starting out from a dead stop.
- most noticeable on inclines/up-slopes
increased (way less effort) acceleration without shoving the throttle to the rug (rig will feel like it's 1000lbs lighter).
ability to use all 6 gears around town (ok, maybe not 1st unless "racing" or starting off on a rather steep incline).
driven "normal" will result in better mpg's around town due to never needing to dip into the throttle much, and not requiring higher rpm under heavy throttle.
decreased need of downshifting on highway, even to pass... except for steeper/longer hills.
easier passing on the highway... often not even requiring a downshift.
Higher numerical gear advantages rock crawling:
never need the throttle to roll out from a stop, even when pointed nearly straight up, simply ease the clutch out to the point the rig starts to stall let off the brake and crawl out. 2 pedal driving.
minimal/no clutch slip/throttle in the really slow/steep/off camber situations.
much slower speed, so when transitioning to clutched, vs stopped/started there is way less lurching/jerking... more stable rig.
Higher numerical gear dis-advantages street driving;
1st gear is not required... maybe on a steep grade from a standstill.
more shifting during city driving (you will use 5 gears... probably not 1st).
increased rpm can be tiring on longer drives... if you can actually hear the engine over the wind/road noise... which in a lifted 37"-tired Wranger is not happening with stock exhaust.
if you drive aggressive, even a little, you will pay at the fuel pump.
Higher numerical gear dis-advantages rock crawling;
0.
none.
nadda.
Anyone that tries to tell you you'll never have the wheelspeed you need when geared too deep...
the 4:1 case and the 2.72 case are withing a few % gear ratios if you simply ignore first with using the 4:1 and 6th when using the 2.72:1.
unless running an automatic, it matters not, select the proper gear in the trans, and way you go.
The same then applies to your axle ratios, select the proper gear and go.
The only times I've wished I had more speed/momentum... it was my own fault for choosing the wrong gear, or the only solution was an automatic.
On the other hand, in situations I wished I could go slower, the only solution was deeper gearing, or, again, and automatic.
Hope all this has helped.
Hardly seems a tough call.
Even with 5.38's it's only a 200rpm difference, and you are still running at less than 2200rpm at 55... say you get frisky and drive 10mph over all the way to work... still under 2600rpm.
I ran my 2013 (3.6, 6spd rubi) with 5.13's on 35's(34") for 2 years... for one of those years I was doing 75-80mph for an ~hour straight on my way to work, and home again. cruise rpm was 3000-3200rpm.
Jeep never missed a beat. If I recall, low 18mpg acting like that, and if I held it to 70mph then high 18mpgs... occasional 19mpg if the wind was in my favour...
I recently went to 37's, and, really miss the zip I had with 35's/5.13's... makes me want 5.38's...
So, in my opinion, if you are definitely going to 37's, just go 5.38's and be done with it.
And, as far as the rubi 4:1, with the 6sp, even on 35's with the 5.13's there were times I wanted even lower gearing... so, I'd not be concerned about making teh t-case "too low" or, "useless".
Edit...
Since you asked to have explained advantages of going one way or another, I'll offer my experience/observations, related directly to a standard trans Jeep that is used for commuting and rock crawling.
Higher numerical gear advantages street driving;
minimal clutch slip/throttle (no throttle required) required when starting out from a dead stop.
- most noticeable on inclines/up-slopes
increased (way less effort) acceleration without shoving the throttle to the rug (rig will feel like it's 1000lbs lighter).
ability to use all 6 gears around town (ok, maybe not 1st unless "racing" or starting off on a rather steep incline).
driven "normal" will result in better mpg's around town due to never needing to dip into the throttle much, and not requiring higher rpm under heavy throttle.
decreased need of downshifting on highway, even to pass... except for steeper/longer hills.
easier passing on the highway... often not even requiring a downshift.
Higher numerical gear advantages rock crawling:
never need the throttle to roll out from a stop, even when pointed nearly straight up, simply ease the clutch out to the point the rig starts to stall let off the brake and crawl out. 2 pedal driving.
minimal/no clutch slip/throttle in the really slow/steep/off camber situations.
much slower speed, so when transitioning to clutched, vs stopped/started there is way less lurching/jerking... more stable rig.
Higher numerical gear dis-advantages street driving;
1st gear is not required... maybe on a steep grade from a standstill.
more shifting during city driving (you will use 5 gears... probably not 1st).
increased rpm can be tiring on longer drives... if you can actually hear the engine over the wind/road noise... which in a lifted 37"-tired Wranger is not happening with stock exhaust.
if you drive aggressive, even a little, you will pay at the fuel pump.
Higher numerical gear dis-advantages rock crawling;
0.
none.
nadda.
Anyone that tries to tell you you'll never have the wheelspeed you need when geared too deep...
the 4:1 case and the 2.72 case are withing a few % gear ratios if you simply ignore first with using the 4:1 and 6th when using the 2.72:1.
unless running an automatic, it matters not, select the proper gear in the trans, and way you go.
The same then applies to your axle ratios, select the proper gear and go.
The only times I've wished I had more speed/momentum... it was my own fault for choosing the wrong gear, or the only solution was an automatic.
On the other hand, in situations I wished I could go slower, the only solution was deeper gearing, or, again, and automatic.
Hope all this has helped.
Last edited by Mike H.; 10-12-2018 at 02:14 PM.
10-15-2018, 12:29 PM
#13
JK Enthusiast
The higher you go numerically the smaller the pinion and on your baby axles that can, does and has led to broken gears. The drive ratio is a short sighted view of a bigger issue. Stick with 4.88's on Dana 30/44. If you want a deeper gear stick to 35's. As Dirt man said you will be much farther ahead in the long run. I'm on 37's and 4.88's but on my 44's I have trussed them, C Gussets, installed new axles (RCV's and TEN Factory) Upgraded all the steering components etc. etc. I like the 37's but things add up. Don't forget brakes and realistically throwing a ram upfront. The list goes on.... Good luck.
10-18-2018, 11:10 AM
#14
JK Super Freak
Join Date: Jun 2008
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The higher you go numerically the smaller the pinion and on your baby axles that can, does and has led to broken gears. The drive ratio is a short sighted view of a bigger issue. Stick with 4.88's on Dana 30/44. If you want a deeper gear stick to 35's. As Dirt man said you will be much farther ahead in the long run. I'm on 37's and 4.88's but on my 44's I have trussed them, C Gussets, installed new axles (RCV's and TEN Factory) Upgraded all the steering components etc. etc. I like the 37's but things add up. Don't forget brakes and realistically throwing a ram upfront. The list goes on.... Good luck.
Myself, I am currently running 4.10's with 35's, and it's not a happy place to be....so I am planning to regear to 5.13's. There is a very small chance that I may run 37's in the future, but with the number of road miles that my rig sees I think staying on 35's is more likely. The 5.13's are perhaps shorter than what is supposed to be "right" but since I do tow a trailer and my rig has the old 3.8 in it, I'll happily cruise at a lower speed in order to have better gearing for on-trail and have the gearing to put all 6 gears in the manual to work (6th is really just a downhill gear for me right now).
And yeah....there's probably a blower in my future anyways.
10-22-2018, 07:13 AM
#16
JK Newbie
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Cool, because I actually dont mind how it feels right now since I do have the Rubicon edition and like how Im able to just cruise up the hills on the road to the trails
10-22-2018, 10:17 AM
#17
Super Moderator
I'm running 5.13s on 37s. It's definitely a little dump-trucky on the highway but I'm fine with it. Keeps me closer to the speed limit. It's great in the rocks though. I went straight from the stock Rubicon 4.10s so I can't comment on any ratio in between, but I don't think I'd go any higher (lower) than 5.13 for a daily driver.