Why should I regear?

[Joe's_Roxy]

I know this is an old post but do you have a manual transmission or auto? I'm considering regearing my rubicon 3.6 with 6mt but I don't know if it's worth going to 4.56 and if 4.88 would be to much. I drive highway alot but I'm constantly down shifting from 6th to 4th on hills and I see alot of them. Thanks

Hey Mac, Depends on tire size. On my 2018 JLR, I put 315/70-R17 Patagonia MT02s on it. Off-roaded in Palo Duro Canyon this spring and decided I needed to regear. I went with 4.88s to get the lower crawl ratio. Not, my 1st gear - 4-low is AWESOME. I just point and go at any obstacle I want. I usually off-road in 4-low 2nd or 3rd gear if the terrain isn't too bad.

On the highway with the 4.88s, I am seeing 6th gear at 60 mph around 2k rpms. And I can get 20 mpgs out of the 3.6.

I am very pleased going with the 4.88s overall!

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[Mac2457]

What size tires are you running?

Sorry, should have mentioned I upgraded to 35x12.5's.

 

[Mac2457]

Hey Mac, Depends on tire size. On my 2018 JLR, I put 315/70-R17 Patagonia MT02s on it. Off-roaded in Palo Duro Canyon this spring and decided I needed to regear. I went with 4.88s to get the lower crawl ratio. Not, my 1st gear - 4-low is AWESOME. I just point and go at any obstacle I want. I usually off-road in 4-low 2nd or 3rd gear if the terrain isn't too bad.

On the highway with the 4.88s, I am seeing 6th gear at 60 mph around 2k rpms. And I can get 20 mpgs out of the 3.6.

I am very pleased going with the 4.88s overall!

What rpm's would you see 70-75ish? I live in NY and if I do 60 I would get run off the road lol.

 

[Joe's_Roxy]

What rpm's would you see 70-75ish? I live in NY and if I do 60 I would get run off the road lol.

I believe it was around 2500 rpm. Well within the power band of the 3.6. I do mostly back roads and don't drive mine on the interstate much.

 

[Mac2457]

I believe it was around 2500 rpm. Well within the power band of the 3.6. I do mostly back roads and don't drive mine on the interstate much.

Great, thank you. I've been looking for real world experience. I do frequent the interstate alot but also going from the Hudson Valley over the Bear mountain regularly I'm forever shifting. I also do pull a trailer occasionally also and it makes the shifting even more frequent. I appreciate your insight, it was a big help thanks!

 

[grimmjeeper]

Sorry, should have mentioned I upgraded to 35x12.5's.

4.56 would be adequate. 4.88 would be good too. The XR package comes from the factory with 4.88s and 35s with the manual transmission. So keep that in mind.

 

[Mac2457]

4.56 would be adequate. 4.88 would be good too. The XR package comes from the factory with 4.88s and 35s with the manual transmission. So keep that in mind.

Thank you for the reply. I do pull a light trailer from time to time also. I feel like the 4.88's would be better. My only concern was highway Rpm's between 70-75 but that concern was address.

 

[grimmjeeper]

Thank you for the reply. I do pull a light trailer from time to time also. I feel like the 4.88's would be better. My only concern was highway Rpm's between 70-75 but that concern was address.

Yeah, I'd go with 4.88s for trailer duty, no question.

 

[JeepinPete]

Moving from 4.10's to 4.88 with your tire size will kick the RPM's of 6th gear 130 rpm higher than your current 5th gear at 75 mph. 4.56 would bring them within 25 rpm. Try driving around in 5th for awhile and see how it feels.

I've been playing around with running 4th, 5th and 6th at highway speeds for the last year or so, 4.10's w/ 37's. I have no difference in mpg in 5th or 6th, 4th is a little worse primarily because it will not "coast" (for lack of a better word) downhill as well at higher rpms. I cannot hear or feel the increase of rpm at highway speed in my Jeep until it is over 3k rpm. Wind noise drowns out any engine noise.

 

[Mac2457]

Moving from 4.10's to 4.88 with your tire size will kick the RPM's of 6th gear 130 rpm higher than your current 5th gear at 75 mph. 4.56 would bring them within 25 rpm. Try driving around in 5th for awhile and see how it feels.

I've been playing around with running 4th, 5th and 6th at highway speeds for the last year or so, 4.10's w/ 37's. I have no difference in mpg in 5th or 6th, 4th is a little worse primarily because it will not "coast" (for lack of a better word) downhill as well at higher rpms. I cannot hear or feel the increase of rpm at highway speed in my Jeep until it is over 3k rpm. Wind noise drowns out any engine noise.

Thanks, I'll check that out. Honestly I spend alot of my time in 4th and 5th anyway but still, as soon as I hit an incline I lose momentum and there is nothing behind the pedal so I need to down shift. Sometime even to 3rd in certain situations. I bought a manual because I enjoy rolling through the gears but I just feel its to much to the point where it's annoying sometimes lol.

 

[grimmjeeper]

Thanks, I'll check that out. Honestly I spend alot of my time in 4th and 5th anyway but still, as soon as I hit an incline I lose momentum and there is nothing behind the pedal so I need to down shift. Sometime even to 3rd in certain situations. I bought a manual because I enjoy rolling through the gears but I just feel its to much to the point where it's annoying sometimes lol.

I had a manual 3.6 in my JK. I enjoyed it a lot less than I thought I would.

With all of the clutch issues in the JL, I wouldn't even consider a manual again. But then the diesel came out. I may have considered a manual with a diesel but it wasn't an option.

Rowing gears is a lot more fun when the engine has even a little torque below 2,000 RPM.

 

[Mac2457]

I had a manual 3.6 in my JK. I enjoyed it a lot less than I thought I would.

With all of the clutch issues in the JL, I wouldn't even consider a manual again. But then the diesel came out. I may have considered a manual with a diesel but it wasn't an option.

Rowing gears is a lot more fun when the engine has even a little torque below 2,000 RPM.

Funny you said that. My jeep is in the shop right now for the clutch. I had the recall done earlier this year and I kept hearing a vibration (best way to describe it) while downshifting. It was far and fiew between and I meant to get in in sooner but I have a hard time finding the time to be without my wheels. A couple of weeks ago I was moving my empty trailer from one side of my house to the other and I got the overheating clutch warning.
I'm annoyed they won't do any other power plants with the manual. I keep praying for a 5.7 but I'm sure it will still be out of my price range...My next jeep, if I decide to get another one, will likely be an automatic.

 

[Jeep Junkie]

I think 35's on stock gears is bad for the longterm health of your engine and transmission because they have to work hard. 35's will make your tranmission fluid and engine coolant run at higher temperatures. Regearing removes that extra stress from them. $3000 for regear is still cheaper than a new transmission and engine. Plus regearing makes your Jeep zippy. By the way, I paid $1,700 for 4.88 Dana gears and $1000 for Eaton front eLocker, so $2,700. Shop around!

 

[Zandcwhite]

I think 35's on stock gears is bad for the longterm health of your engine and transmission because they have to work hard. 35's will make your tranmission fluid and engine coolant run at higher temperatures. Regearing removes that extra stress from them. $3000 for regear is still cheaper than a new transmission and engine. Plus regearing makes your Jeep zippy. By the way, I paid $1,700 for 4.88 Dana gears and $1000 for Eaton front eLocker, so $2,700. Shop around!

The engine doesn't work any harder because it doesn't know wether the gearing is coming from the axle or the transmission. It sees the exact same load with 3.45 gears in 6th, 4.10 gears in 7th, or 5.13 gears in 8th because they all have the same final drive ratio at that point. The transmission doesn't work any harder in 4th gear than it does in 8th gear. The 3.45s that come in a sahara or sport with 32" tires is mathematically equivalent to 4.10s and 38s. Some prefer ultra deep gears, but you certainly don't need them with this transmission. That's just not how it works.

 

[grimmjeeper]

The engine doesn't work any harder because it doesn't know wether the gearing is coming from the axle or the transmission. It sees the exact same load with 3.45 gears in 6th, 4.10 gears in 7th, or 5.13 gears in 8th because they all have the same final drive ratio at that point. The transmission doesn't work any harder in 4th gear than it does in 8th gear. The 3.45s that come in a sahara or sport with 32" tires is mathematically equivalent to 4.10s and 38s. Some prefer ultra deep gears, but you certainly don't need them with this transmission. That's just not how it works.

The one factor that can come into play is the lockup feature of the torque converter.

Modern transmissions with good computer control are better than they used to be. But if you have a big mismatch like 3.45 gears and 35s, you may end up with the computer never locking up the torque converter. That reduces efficiency and generates extra heat. If your cooling system can handle it, it's not a huge deal. But it's less than ideal.

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