Mojave should come with 4.56 gears 4.10s dont cut it

[Zachanadandy]

My Mojave with 4.10 gears and 37s stays in 6th gear or below most of the time. I recently took a trip to the mountains, and interstate driving saw some time in 7th gear. I honestly never saw the Jeep go into 8th gear in the 8-hour round trip. I'm going to hold off re-gearing until my 37s wear out, then I am going with 40s and a re-gear.

8+ hour drives are very common for us being our AZ property is 540 miles from the house. 37s and 4.10s it sees 8th all the time. Cruise control is usually set at 80-85mph. Headwind, hills, etc it's immediately 7th and sometimes 6th. But downhill or tailwinds and it's right back in 8th. I've seen 8th in the dirt out in the desert plenty of times. If I went to 40s I'd regear, but no need at this point. I don't know how people aren't seeing 8th? Uphill both ways? Never drive over 60mph? I couldn't take a trip without seeing 8th of I tried.

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[Splenda]

8+ hour drives are very common for us being our AZ property is 540 miles from the house. 37s and 4.10s it sees 8th all the time. Cruise control is usually set at 80-85mph. Headwind, hills, etc it's immediately 7th and sometimes 6th. But downhill or tailwinds and it's right back in 8th. I've seen 8th in the dirt out in the desert plenty of times. If I went to 40s I'd regear, but no need at this point. I don't know how people aren't seeing 8th? Uphill both ways? Never drive over 60mph? I couldn't take a trip without seeing 8th of I tried.

Maybe it's the 94 pound tires and 30 pound wheels? :-/

 

[Zachanadandy]

Maybe it's the 94 pound tires and 30 pound wheels? :-/

I'm sure that doesn't help, but even there downhill should be low enough load for 8th?

 

[Splenda]

I'm sure that doesn't help, but even there downhill should be low enough load for 8th?

I don't recall ever seeing 8th gear before I swapped out the wheels and tires.

 

[Salty Dave]

I won’t pretend to know what is right for everyone. I can only speak to my experience. My 2020 JTR with 37’s and 4.10’s was miserable, seldom seen 7th mostly 6th at 75 mph. Regeared to 5.38’s it would still go to 7th on slight inclines, but would mostly run in 8th. Had modest mpg gain over several different driving conditions. When I say modest I’m talking 6/10 mpg. The benefit for me was only seen when towing.

My 2025 JTR stock configuration at 75 mph seldom shifts to 8th. I’m hoping this will improve with more miles on it.

I’ve read so many accounts of people experiencing much better mileage and using higher gears than I do. At times I feel like my experience is not the norm.

I plan on putting 7,500 miles on the new one before switching to 37’s. At that time I will either leave it with the 4.10’s or change to 5.13’s. I will not go as low as 5.38’s.

 

[Splenda]

I won’t pretend to know what is right for everyone. I can only speak to my experience. My 2020 JTR with 37’s and 4.10’s was miserable, seldom seen 7th mostly 6th at 75 mph. Regeared to 5.38’s it would still go to 7th on slight inclines, but would mostly run in 8th. Had modest mpg gain over several different driving conditions. When I say modest I’m talking 6/10 mpg. The benefit for me was only seen when towing.

My 2025 JTR stock configuration at 75 mph seldom shifts to 8th. I’m hoping this will improve with more miles on it.

I’ve read so many accounts of people experiencing much better mileage and using higher gears than I do. At times I feel like my experience is not the norm.

I plan on putting 7,500 miles on the new one before switching to 37’s. At that time I will either leave it with the 4.10’s or change to 5.13’s. I will not go as low as 5.38’s.

Maybe miles will help. Mine only has 7k miles.

 

[professorkx]

I had thought the motor and AT were the same for all years of Gladiators, but there certainly seems to be disparate experiences with the same gear ratio and tire size. So, is the motor and AT the same for all years? This might explain the differenc

 

[Splenda]

My understanding is that it is healthier for the 3.6 to run at higher RPMs anyways, so maybe they changed the shift strategy to keep the engine at higher RPMs. I am, of course, talking out of my arsehole.

 

[Zachanadandy]

My understanding is that it is healthier for the 3.6 to run at higher RPMs anyways, so maybe they changed the shift strategy to keep the engine at higher RPMs. I am, of course, talking out of my arsehole.

Healthier under load doesn't mean healthier all the time or they wouldn't have wasted money with the 2 stage oil pump and they'd set the idle at 2500rpm. 8th gear is only intended for light loads, flat, downhill, etc. With 37s 4.56s are a better match for it to work as designed but nobody wants to spend regear money to move 1 gear ratio so they jump the shark and go way deeper than they needed to. Then they are convinced it drives better because it will hold 8th gear even up hills like it was never supposed to.

 

[Badunit]

8th gear is only intended for light loads, flat, downhill, etc.

Then they are convinced it drives better because it will hold 8th gear even up hills like it was never supposed to.

Doesn't holding 8th indicate that the transmission is under "light load"? Otherwise it would downshift to 7th or 6th as designed, right? The engine has plenty additional rpms to give, no one modified the transmission and nothing external is forcing it to stay in 8th, it doesn't feel the need to downshift because the load is still "light".

 

[Zachanadandy]

Doesn't holding 8th indicate that the transmission is under "light load"? Otherwise it would downshift to 7th or 6th as designed, right? The engine has plenty additional rpms to give, no one modified the transmission and nothing external is forcing it to stay in 8th, it just doesn't feel the need to downshift.

Holding 8th at higher rpms because you geared to the moon? Vs shifting into 9th? The math is simple and Jeep didn't spend thousands of hours testing with different gear ratios with infinite gearing options and then just choose 4.10s for 33s at random. 4.56 gears are the nearest to stock option you have for 37s. If you want a little more than stock I could see 4.88s. 5.38s like one guy ran? Hard no. It holds 8th for sure. We went 5.38s on 38s in our JLUR. Biggest waste of money I've ever spent on a mod period. It was in 8th by 40mph. It held 8th on the freeway unless you were climbing a legit grade. That doesn't prove it's under light load, that proves that it's out of shifts. Why have an 8 speed when you're in top gear by half the legal speed limit? 0-60 was the same. Around town mpg was up by 1 mpg. Freeway it was down 2-3mpg. I don't know about you but I burn a lot more fuel on a roadtrip than I do driving around town in a month so I'll take better freeway mpg any day. Again, I'm not saying there's never a case for regearing, but small changes aren't worth the cost and going to extremes is worse than running stock 4.10s and 37s from my experience having run lots of combos in modern Jeeps.

 

[ShadowsPapa]

and Jeep didn't spend thousands of hours testing with different gear ratios with infinite gearing options and then just choose 4.10s for 33s at random.

You'd be interested in a fast-change differential I found for sale, I believe used by AMC, to test under various ratios and so on. They could swap gears in minutes without much effort.
Sort of wish I had bought it as I also have most of one of their Prestolite distributor testers from the old plant in Kenosha as well as a few other tools and such.

The flip side of overloading at low RPM is running an engine at a higher RPM than needed is fuel, of course, but also wear.
Jeep figured the sweet spot, and that includes for cooling and more (the RPM of the water pump, fuel burned vs. ability of the cooling system to remove the BTUs generated)

 

[Badunit]

...It held 8th on the freeway unless you were climbing a legit grade. That doesn't prove it's under light load, that proves that it's out of shifts.

2200-2500 rpm is far from red line; it is not "out of shifts" (downshifts, that is, which is what we are talking about). Mine downshifts, just not on small hills. It will downshift several gears if I press the accelerator hard enough.

Gearing is a compromise. "Optimum" gearing is an opinion that depends on the criteria used for determining "optimum". My engine is spinning 11% faster than before. Whether the increased rpms causes more wear or the reduced load causes less remains to be seen. It has a small affect on mpg but I don't care, it was not one of my criteria.

 

[ShadowsPapa]

2200-2500 rpm is far from red line; it is not "out of shifts" (downshifts, that is, which is what we are talking about). Mine downshifts, just not on small hills. It will downshift several gears if I press the accelerator hard enough.

Gearing is a compromise. "Optimum" gearing is an opinion that depends on the criteria used for determining "optimum".

He's talking about upshifts. It's out of shifts as it can't go any higher.
If running 2500 RPM on the highway with no load, you're wearing that engine a heck of a lot faster than the rest of us.

 

[Badunit]

He's talking about upshifts. It's out of shifts as it can't go any higher.
If running 2500 RPM on the highway with no load, you're wearing that engine a heck of a lot faster than the rest of us.

But we were talking about downshifts and "light loads" and how not downshifting appears to indicate the transmission is under a light enough load (otherwise it would downshift, right?). Upshifting is a totally different subject. We can easily all agree that once it is in 8th it has nowhere higher to go.

I don't know what else to say on this subject. A lot of space has been taken up by this back-and-forth between the three of us. Both/all sides have said their piece, repeatedly. No resolution or concurrence is in sight. I'll try to not respond to any future replies in this thread, if I can hold my tongue.

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