Gearing.. How much of a seat-of-the-pants difference does it really make?

[Wildlifeguy]

I've read and read, I know the numbers and what they mean. I'm not really concerned about what ratio to go to. I really want to know how big of a difference you actually feel when going lower gears. Currently I have 35s on stock 3.73 gears. I bought it that way new off the lot and never drove one with stock size tires. I came from an ecoboost F150 with the 6 speed. I was used to it hitting top gear soon and set the cruise at 75 and it would not drop down a gear unless I was going up a mountain. It had a massive amount of low end torque. I've now had the gladiator for 5 months and around 6k miles. It feels adequate. On flat ground and no wind, it will cruise in 7th and occasionally 8th. Any hill and it's 6th or 5th. Against the wind, it wont go higher than 6th.. Passing on the highway seems perfectly fine to me. Off the line if just fine. Between 20-50 it feels a little sluggish.

Without considering any other driving conditions or future changes, how much difference would I feel going up to something like 4.56? Is this a night and day difference or just better? I wish I could find someone who has regeared take a ride with them to really feel the difference. Just trying to determine if I should prioritize this change.

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[jay21mojave]

I've read and read, I know the numbers and what they mean. I'm not really concerned about what ratio to go to. I really want to know how big of a difference you actually feel when going lower gears. Currently I have 35s on stock 3.73 gears. I bought it that way new off the lot and never drove one with stock size tires. I came from an ecoboost F150 with the 6 speed. I was used to it hitting top gear soon and set the cruise at 75 and it would not drop down a gear unless I was going up a mountain. It had a massive amount of low end torque. I've now had the gladiator for 5 months and around 6k miles. It feels adequate. On flat ground and no wind, it will cruise in 7th and occasionally 8th. Any hill and it's 6th or 5th. Against the wind, it wont go higher than 6th.. Passing on the highway seems perfectly fine to me. Off the line if just fine. Between 20-50 it feels a little sluggish.

Without considering any other driving conditions or future changes, how much difference would I feel going up to something like 4.56? Is this a night and day difference or just better? I wish I could find someone who has regeared take a ride with them to really feel the difference. Just trying to determine if I should prioritize this change.

Re-Gear good question.. Allow me to suggest go a dealership and test drive a Rubicon/Mojave as they come with 4.10 gears; get a feel for that gearing. Now for costs.. the labor time schedules show somewhere between 11-12 hours; calculate your costs based on local labor rates... you can find parts pricing on line from multiple catalogue vendors.. remember each axle will require a master kit too. Good Luck.

 

[XraytecH]

Re-Gear good question.. Allow me to suggest go a dealership and test drive a Rubicon/Mojave as they come with 4.10 gears; get a feel for that gearing. Now for costs.. the labor time schedules show somewhere between 11-12 hours; calculate your costs based on local labor rates... you can find parts pricing on line from multiple catalogue vendors.. remember each axle will require a master kit too. Good Luck.

I my experiences some will charge extra labor costs if not refuse to install owner supplied parts.

 

[XJADDICTION]

Ok well going to the dealer and driving one with 4:10’s and a 33” tire is not a very good comparison IMOP.

for me I have 37’s and 4:10 factory gears with a Tazer and it drives very well with that set up. Hard passes it will drop to 5th gear and grunts a little but I rarely need to do that in my JT.

I have owned many trucks and Jeeps with larger tires on original gears, then swapping to a lower ratio gear set. They always performed and felt faster after a gear change. I was always pleased with gear swaps, never disappointed and always felt the gear change was worth the money. One of the best mods you can make IMOP.

IMOP you will notice a difference in that with 4:56 gears and 35’s for your JT will drive closer to its original stock performance level maybe a little peppier and a lot less down shifting on the hills.

One thing that makes the JT so good is the 8 speed automatic. If you add a Tazer set for your actual tire diameter, you will notice a much better seat if the pants performance from yourJT. Add a lower gear set and it will improve the drivability to more stock level and if you tow anything you will really notice the difference. If you go off road and use 4Lo you will DEFINITELY notice an improvement!

there’s my 2 pennies worth

 

[Wheelin98TJ]

Best way I can explain it is mathematically.

3.73 to 4.56 is a 22.25% change.

Torque multiplication will be 22.25% greater, RPM will also be 22.25% greater.

 

[CerOf]

Can’t speak to the JT, but regearing my ZJ from 3.73 to 4.56 resulted in 1/2 second gain 0-60.

I bet you’d pick up the same.

Ultimately, you can’t miss what you never had.

 

[Rockabillyroy]

In my JKU auto, I went from 3.73 to 4.56.

3.73 was perfectly fine for around town and off roading. 4.56 made a world of difference on the highway. Especially up long steep hills.

 

[kevman65]

If you just drive around town and off road, you don't need to change a thing.

If you use it as a pavement pounder driving large miles of super slab, you'll notice the difference the first time on the interstate. Then you'll also notice it at the gas pump when you get some extra MPG's.

 

[Mac]

Re-Gear good question.. Allow me to suggest go a dealership and test drive a Rubicon/Mojave as they come with 4.10 gears; get a feel for that gearing. Now for costs.. the labor time schedules show somewhere between 11-12 hours; calculate your costs based on local labor rates... you can find parts pricing on line from multiple catalogue vendors.. remember each axle will require a master kit too. Good Luck.

That’s a good idea, 33s and 4.10s are a little taller than 35s and 4.56s gears but should be pretty close due to the 35s generally being a little heavier than the stock 33s.

 

[Panthers65]

Gearing is, IMO the biggest "bang for your buck" performance wise.

Coming from someone that hasn't regeared yet on 37s(waiting for more locker options for the front), No one that I can remember has ever regretted regearing with larger tires.

 

[shrinkhead]

It’s all relative and should be need based. you gain faster acceleration and you may hold 8th gear longer but your 8th gear will be spinning at 3K RPMs vs 2K so why not just rock 6th at 3K and save the money if not towing ?

p.s. made up those RPMs for illustrative purposes

 

[TwelveGaugeSage]

I don't see anyone else mentioning this, but you can pretty much get the feel without changing anything on your jeep using 4-low.

Find a safe surface to run 4-low in. You can do this on pavement relatively safely as long as you keep it in a straight line and don't go too far, but dirt, sand, or snow would be ideal.


Your current crawl ratio in 1st gear 4-hi is 17.57. This is your normal from launch crawl ratio, Place the transmission into manual 3rd gear. In 4-low this gives a crawl ratio of about 21.30. This is close to what your new first gear would be with 4.56 gears, which is 21.48.

Thus, launching in 3rd gear 4-low is pretty much what launching in 1st gear would feel like if you went to 4.56 gears.

 

[87chief]

I don't see anyone else mentioning this, but you can pretty much get the feel without changing anything on your jeep using 4-low.

Find a safe surface to run 4-low in. You can do this on pavement relatively safely as long as you keep it in a straight line and don't go too far, but dirt, sand, or snow would be ideal.


Your current crawl ratio in 1st gear 4-hi is 17.57. This is your normal from launch crawl ratio, Place the transmission into manual 3rd gear. In 4-low this gives a crawl ratio of about 21.30. This is close to what your new first gear would be with 4.56 gears, which is 21.48.

Thus, launching in 3rd gear 4-low is pretty much what launching in 1st gear would feel like if you went to 4.56 gears.

That is some genius level shit right there.

any equations like that for the 6 speed manual with gearing up?

 

[TwelveGaugeSage]

That is some genius level shit right there.

any equations like that for the 6 speed manual with gearing up?

Hah! All simple math really, but I must admit, I plugged it all into a calculator out of laziness.

Here is the best I can do without going too crazy:
1st with 3.73 has a crawl ratio of 19.13
4.10 is 21.03
4.56 is 23.39
4.88 is 25.03
5.13 is 26.32
5.38 is 27.6

Crawl ratios 4-low 3.73(2.72 t-case):
1st 52.04
2nd 26.58
3rd 15.52

So with 3.73 rear and 2.72 t-case, 4-low 2nd gear will feel very close to 1st gear 4-hi if you went to 5.13 gears.

For the Rubicons:
1st gear crawl ratio is 21.03 as noted above.
Crawl ratios 4-low 4.10(4.0 t-case)
1st 84.13
2nd 43.13
3rd 25.09
4th 16.4


So for those of us with Rubicons, 4-low 3rd gear will feel like 1st gear 4-hi if we went to 4.88s.

Edit: This is why I never understood people saying the 4:1 T-case is TOO short. I can get near the same gear ratios as the 2.72 just by going up a gear.

 

[NachoRuby]

Edit: This is why I never understood people saying the 4:1 T-case is TOO short. I can get near the same gear ratios as the 2.72 just by going up a gear.

It's largely the high speed desert running guys saying that. They max out top speed for 4 low on a Rubicon. Since we have nothing similar around my region of the east coast, I can't imagine running out of gear in 4L, but those that run out west do. That's why jeep gave them the Mojave.

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