488s or 456s. That is the question

[DocMike]

https://www.quadratec.com/c/reference/best-gear-ratio-when-adding-larger-tires

This is the chart.

I apologize. Camper meaning off road pop up. Torn between the two options. I have had fast cars. NO interest in street racing the Jeep. Everyone I talk to wishes they had gone deeper. See post n here about buyers remorse and 5:13.

According to the chart, 4:88 is on the top end of the threshold for best all around....

A RTT would only affect things at speed. It doesn't weigh much, just frontal area and drag. Not sure what you mean by "camper". There are a number of colloquial meanings. A topper? Camping trailer? Something else? Topper won't affect much, trailer might.

Rubicons, Mojaves, and Max Tows have 4.10, and I recall seeing a chart not long ago that had RPM on one axis, tire size on another, and R&P at the intersections. Too low or too high were colored somehow to warn away, and there was a range of happiness. 35" tires had a happiness range of 4.10, 4.56, and 4.88. Looking at other ratios and tire sizes that Jeep is known to have used stock, the 4.10 with 35"s corresponded with the stock ratio on the lesser trims. Essentially by their logic, it's the fuel economy oriented choice. If you didn't care for the stock on stock in a non-Rubicon/Mojave/Max Tow, you'll be similarly unhappy with 4.10s on 35s (though you'll not lose your capacities). Accordingly, 4.56 would be your "all rounder", and 4.88 would be for power.

Another meaningful datapoint might be that being able to bolt on 35"s was a design parameter. They assume different trims are to be used differently, and the Rubicon trim is the one most likely to be used that way. 4.10 should work according to that design parameter, but there's always that "how well" element.

When I eventually get my truck (a Rubicon), I'll be putting 35s on it. I'll give the 4.10s a shot, and expect to be happy with them. I've DDd a number of cars over the years with double digit horsepower, and don't drive very fast in trucks (there are other cars for that). If it can't do what I need it to do as a truck, I'll reassess gearing, but otherwise I'll take it easy and enjoy the fuel savings.

Sponsored

 

[WK2JT]

Everyone I talk to wishes they had gone deeper.

Exactly… I’ve never heard, “wish I hadn’t gone so deep.” No amount of gears will turn it into a race car, but merging, towing, and mountain driving are vastly improved.

DocMike, I’m in Highlands Ranch if you want to come drive mine. You may not be looking at 37’s, but it will give you an idea.

 

[LostWoods]

how many folks have you ever heard say they wish they hadnt gone so deep on their regear?

Survey Says:

None

4.88 for 35”
5.13 for 37”

love my 5.13 with pedal commander. No regrets whatsoever. So thankful I didn’t play it safe and go with 4.88. Acceleration is outstanding, gotta be careful to not spin the tires. Highway cruise is easy 8th gear with plenty of passing power. MPG is who knows, I didn’t buy a brick shaped vehicle and expect to get good fuel economy.

People need to realize these aren't the old Jeep slushboxes. That .67 OD on the 8AT is deep and can push some seriously short gears. I mean the fact that 5.13s on 35s is a reasonable combination is just disgustingly awesome.

I've never met anyone who regretted going too deep, but almost everyone who waffled and not committed complained and wished they went deeper.

 

[spectre6000]

Admittedly not on a Jeep, but I have seen people regretting deep gearing. Different application, platform, and all sorts of stuff though. You definitely can go too deep, just probably not within the bounds of this conversation.

@DocMike , that looks like the chart. Thanks for the memory refresher. Looks like a slight mis-remembering on my part. Mistake admitted. It does, however, reinforce the observation re: Jeep's own specification of 4.56/4.88 and the associated logic and performance comparison. 4.10 w/ 33"s (stock Rubicon) is in the same "Daily Driver, Best Overall Performance" range as 4.56 w/ 35"s. Further, if you're OK with being slow in favor of fuel economy (personally, that's my M.O. with trucks), the 4.10 (or 4.11 in the chart) corresponds to the middle of the "Highway Driving, Good Fuel Economy" column. You have to drive it like it is what it is, and keep your foot out of it though. No jackrabbit starts, plan ahead, etc. I admit some consternation about the regular slogs up and down 285 with the tall gears and altitude though (I really wish forced induction were an easy. I'll have to see how it does. I may wait a few K miles before upgrading tires to really let the engine, etc. break in properly.

@WK2JT , look west and squint, and you might see me waiving from Deer Creek Canyon!

 

[DocMike]

Man, we are not here to tear each other down. It's a community and we are all here to learn together. No need to apologize.
I know what you mean about too deep. I had a buddy with a nasty hot rod. Model T. Would "redline at 80mph but do a wheelie all the way there." Bit of hyperbole, but he kept it under a cover and only went out for hooligan stuff then right back in the garage.

I'm really leaning 4:88. at 15K on my odometer I think I am broken in. With the altitude and heavy wheels....Those Black Rhinos are 40 pounds each. I'm seeing about 17.8-17.6 Mpg when I drive around town. Not bad. But I do notice it takes more to get her going. Then once she is rolling things are fine.

Admittedly not on a Jeep, but I have seen people regretting deep gearing. Different application, platform, and all sorts of stuff though. You definitely can go too deep, just probably not within the bounds of this conversation.

@DocMike , that looks like the chart. Thanks for the memory refresher. Looks like a slight mis-remembering on my part. Mistake admitted. It does, however, reinforce the observation re: Jeep's own specification of 4.56/4.88 and the associated logic and performance comparison. 4.10 w/ 33"s (stock Rubicon) is in the same "Daily Driver, Best Overall Performance" range as 4.56 w/ 35"s. Further, if you're OK with being slow in favor of fuel economy (personally, that's my M.O. with trucks), the 4.10 (or 4.11 in the chart) corresponds to the middle of the "Highway Driving, Good Fuel Economy" column. You have to drive it like it is what it is, and keep your foot out of it though. No jackrabbit starts, plan ahead, etc. I admit some consternation about the regular slogs up and down 285 with the tall gears and altitude though (I really wish forced induction were an easy. I'll have to see how it does. I may wait a few K miles before upgrading tires to really let the engine, etc. break in properly.

@WK2JT , look west and squint, and you might see me waiving from Deer Creek Canyon!

 

[WK2JT]

Admittedly not on a Jeep, but I have seen people regretting deep gearing. Different application, platform, and all sorts of stuff though. You definitely can go too deep, just probably not within the bounds of this conversation.

@DocMike , that looks like the chart. Thanks for the memory refresher. Looks like a slight mis-remembering on my part. Mistake admitted. It does, however, reinforce the observation re: Jeep's own specification of 4.56/4.88 and the associated logic and performance comparison. 4.10 w/ 33"s (stock Rubicon) is in the same "Daily Driver, Best Overall Performance" range as 4.56 w/ 35"s. Further, if you're OK with being slow in favor of fuel economy (personally, that's my M.O. with trucks), the 4.10 (or 4.11 in the chart) corresponds to the middle of the "Highway Driving, Good Fuel Economy" column. You have to drive it like it is what it is, and keep your foot out of it though. No jackrabbit starts, plan ahead, etc. I admit some consternation about the regular slogs up and down 285 with the tall gears and altitude though (I really wish forced induction were an easy. I'll have to see how it does. I may wait a few K miles before upgrading tires to really let the engine, etc. break in properly.

@WK2JT , look west and squint, and you might see me waiving from Deer Creek Canyon!

You’re welcome to come drive mine too. I think everyone here who has done gears went through what you guys are debating. The data doesn’t necessarily add up to the real world outcome. There are just so many variables that affect the experience. I was originally going with 4.88’s for 37’s because I was so worried about 5.13’s based on charts and calculators. Now look at me wishing I had gone 5.38’s.

 

[DanW]

I chose 35s and 4.88s
It’s my understanding a dealer won’t flash the pcm any longer

I also used a reputable shop and let them source the gear. I figure if there is an issue it’s easier to get them to fix it that way

At 15k I’m sure any shop would want you to replace the bearings for the carrier ect

Mine only has a few hundred miles on it and there not doing it as far as I know

How are you liking the 488's and 35's? What rpm are you turning at 75mph? I've got a manual JLUR with the 6 speed and am deciding between 4.56 and 4.88's. It's not bad now with 4.10, but I just want 6th gear to be more usable without making 1st too short. Right now I'm thinking 4.56's are the sweet spot, but haven't heard from anyone running 4.88's until now. I'd love to hear your feedback after living with it a bit.

 

[Blade1668]

I'll throw out some of my stuff with my Jeeps. My 91 MJ and XJ have 3:55 stock gears stop tire size is about 29-30 in, LJ "6 speed stick" stock with 3:73 came with 30 in tires (31 tires put speedometer on) my rock crawler XJ I regeared 4:56 w front locker and Trac-Loc rear ran 33s (steel wagon wheels rims AKA heavy) it put speedometer on. Ran great on trails like a goat planned on going with 35-36 in tires was "trying to wear out 33 first" currently the 33s are on LJ it's slightly doged on road.
When I put the 4:56 gears in "everybody" (except a older Jeeper and speed shop owner) said it was to low for 35s I don't think so. That was of the tech 20 or so years back. Dang I'm getting old.
Now one thing that does become a problem can be pinion gear size on deep gearing that could become a issue and the weak link. I wouldn't go to a 4:88 or lower with old D44 axles due to pinion gear size maybe with the "new" D210 in the JT's I'm not sure. That was a big reason many go to D60's not just axle shaft size but for larger pinion.

 

[DanW]

I'll throw out some of my stuff with my Jeeps. My 91 MJ and XJ have 3:55 stock gears stop tire size is about 29-30 in, LJ "6 speed stick" stock with 3:73 came with 30 in tires (31 tires put speedometer on) my rock crawler XJ I regeared 4:56 w front locker and Trac-Loc rear ran 33s (steel wagon wheels rims AKA heavy) it put speedometer on. Ran great on trails like a goat planned on going with 35-36 in tires was "trying to wear out 33 first" currently the 33s are on LJ it's slightly doged on road.
When I put the 4:56 gears in "everybody" (except a older Jeeper and speed shop owner) said it was to low for 35s I don't think so. That was of the tech 20 or so years back. Dang I'm getting old.
Now one thing that does become a problem can be pinion gear size on deep gearing that could become a issue and the weak link. I wouldn't go to a 4:88 or lower with old D44 axles due to pinion gear size maybe with the "new" D210 in the JT's I'm not sure. That was a big reason many go to D60's not just axle shaft size but for larger pinion.

What I'm hearing from guys that do the installation is that they recommend up to 4.88's but that the pinions get a bit small for their comfort at 5.13 and up. But each has also said they've not seen anyone break 5.13's, either. It just makes them nervous.

I'm waiting around on the JL side of the forum for someone with the manual, 35's, and 4.88's to give a review before my final decision, but I'm leaning toward 4.56 right now. I'm pretty happy with all of the gearing except for 6th. I'd like it to be more useable, which would push 5th into a better spot for going up steeper roads and lessen the frequency of downshifting to 4th. But I don't want first gear to become too short, either. With 4.10's, it is already pretty short.

Did you re-gear your JT? If so, what gears, tire size, and transmission do you have?

 

[Blade1668]

What I'm hearing from guys that do the installation is that they recommend up to 4.88's but that the pinions get a bit small for their comfort at 5.13 and up. But each has also said they've not seen anyone break 5.13's, either. It just makes them nervous.

I'm waiting around on the JL side of the forum for someone with the manual, 35's, and 4.88's to give a review before my final decision, but I'm leaning toward 4.56 right now.

Did you re-gear your JT? If so, what gears, tire size, and transmission do you have?

My JT is stock, Max-Tow on factory tires n rims. But will probably go to 33in tires if not 34-35in later but not soon and maybe 2 in spacers too. Lacking on some clearance. It's my D.D. being I've got a few Jeeps, I need to get back to swapping parts over for 90XJ to 91 XJ
By the way I drove though IN. today. Oddly enough heading back to Danville AL.

 

[LostWoods]

What I'm hearing from guys that do the installation is that they recommend up to 4.88's but that the pinions get a bit small for their comfort at 5.13 and up. But each has also said they've not seen anyone break 5.13's, either. It just makes them nervous.

I'm waiting around on the JL side of the forum for someone with the manual, 35's, and 4.88's to give a review before my final decision, but I'm leaning toward 4.56 right now. I'm pretty happy with all of the gearing except for 6th. I'd like it to be more useable, which would push 5th into a better spot for going up steeper roads and lessen the frequency of downshifting to 4th. But I don't want first gear to become too short, either. With 4.10's, it is already pretty short.

Did you re-gear your JT? If so, what gears, tire size, and transmission do you have?

You do lose a pinion tooth from 4.88 > 5.13 I believe but I'm not sure I'd be worried on 35s or even 37s as long as you're not going full send all day long. The pinion shafts are massive compared to the JK D44 (see below, those are both 5.38s) and the teeth are wider/shallower than in the past which adds a lot of strength against shearing.

 

[spectre6000]

For those not at altitude in the conversation, it's worth noting that @DocMike is short 51 hp right off the bat, @WK2JT is down 43 hp (assuming he's at 5K'), and I'll eventually shave fully 60 hp (an entire VW beetle, and a late production, most powerful engine they got version at that)... Air density decreases at a rate of 3% per 1K' above sea level, and that directly correlates to reduced power. Our gearing conversations have a slightly different underpinning, and may not apply 100% to OP or anyone else down in the "way flats".

 

[DanW]

For those not at altitude in the conversation, it's worth noting that @DocMike is short 51 hp right off the bat, @WK2JT is down 43 hp (assuming he's at 5K'), and I'll eventually shave fully 60 hp (an entire VW beetle, and a late production, most powerful engine they got version at that)... Air density decreases at a rate of 3% per 1K' above sea level, and that directly correlates to reduced power. Our gearing conversations have a slightly different underpinning, and may not apply 100% to OP or anyone else down in the "way flats".

Thank you for pointing that out! I hadn't thought of it and it is an important consideration.

 

[WK2JT]

For those not at altitude in the conversation, it's worth noting that @DocMike is short 51 hp right off the bat, @WK2JT is down 43 hp (assuming he's at 5K'), and I'll eventually shave fully 60 hp (an entire VW beetle, and a late production, most powerful engine they got version at that)... Air density decreases at a rate of 3% per 1K' above sea level, and that directly correlates to reduced power. Our gearing conversations have a slightly different underpinning, and may not apply 100% to OP or anyone else down in the "way flats".

For those not at altitude in the conversation, it's worth noting that @DocMike is short 51 hp right off the bat, @WK2JT is down 43 hp (assuming he's at 5K'), and I'll eventually shave fully 60 hp (an entire VW beetle, and a late production, most powerful engine they got version at that)... Air density decreases at a rate of 3% per 1K' above sea level, and that directly correlates to reduced power. Our gearing conversations have a slightly different underpinning, and may not apply 100% to OP or anyone else down in the "way flats".

I completely agree with this. It is one of the variables to consider. However, I will say I already wanted 5.38's with the 37's before I left Atlanta at 1,000' (I keep mentioning 37's as I know the OP is talking about 35's). Are the 5.13's the wrong gear for my setup, certainly not. However, I was still wishing I went deeper after being worried 5.13's were already too deep. Add in the elevation that spectre6000 points out and it just made me want them that much more. The higher your elevation, the more you will want to lean on going deeper. If you're at sea level, your margin for acceptable gear ratios is a little wider and more forgiving. Just don't worry yourself into going too conservative. I bring all of this up to help anyone considering gears as I know the anxiety it can cause and if you're ever in the Denver area, feel free to contact me. Best cure for all of this is forced induction.

 

[WK2JT]

You do lose a pinion tooth from 4.88 > 5.13 I believe but I'm not sure I'd be worried on 35s or even 37s as long as you're not going full send all day long. The pinion shafts are massive compared to the JK D44 (see below, those are both 5.38s) and the teeth are wider/shallower than in the past which adds a lot of strength against shearing.

So I believe this was true for the JK D44 axles, but I'm fairly certain the AdvanTEK D44's in the JL/JT all use the same 8 tooth pinion for 4.88, 5.13 and 5.38. Only the tooth count on the ring gear changes (39, 41, and 43 respectively). 4.56 has a 9 tooth pinion and the 4.10 picks up 10 teeth. Don't quote me on that as Dana has updated their site and it no longer lists the specifics for any ratio above 4.10, but you can count the teeth in the pictures lol. Agreed thought... you should be fine unless you are going crazy. In that case, take a look at dynatrac or currie axels.

https://spicerparts.com/parts/axle/...ring-and-pinion-gearing-for-jeep-gladiator-jt

Sponsored