Atlas 4-speed gearing

HenikonLJ

HenikonLJ

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So after yesterday's snow wheeling adventure I've decided the Rubicon 4-1 case is to low sometimes and I need another low range.
With the 6 speed I found myself either in low range 4-5th gear and revving out more than I want. But in high I was in 1st-2nd and stalling out sometimes.
So with that issue I've decided I want to do a doubler of some sort but because I'm not auto a Rubicrawler is out of the question so that leaves something aftermarket like the atlas 4 speed.
Now the question is what gearing would be worth it. Part of me thinks the 11.70 over the 10.34 what say the people who run an atlas?
 
The 3.8:1 4 speed Atlas would probably work, you will have to do some driveshaft modifications. I run a 3.8:1 2 speed Atlas behind a small block chevy, turbo 350 and 4:88 diff gears, it serves me well.
 
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What is your tire size? What are your axle gears?

If you stall out in first,in snow that is telling me your axle gears are wrong
 
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Rickyd said:
What is your tire size? What are your axle gears?

If you stall out in first,in snow that is telling me your axle gears are wrong
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I know my axle gears are not correct but that's not my current issue. The 4-1 is to low and 1-1 is to high I need something in between like a 2.72. so the question now is what should the new gearing be behind the 2.72 a 3.8 or a 4.3.

To directly answer your question 4.10 and 35s completely aired down. Not going to waste my time putting money into the axles when I'm building tons for it.
 
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Mike_H said:
I had the same issue with a 5-speed and the Rubicon t-case. The auto swap fixed it all. 4 Hi is very usable again.
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Yeah I wouldn't mind doing a auto but the manual is great for what I do currently. Rather not have money tied up into something that works good sofar
 
mrblaine said:
If you won't "waste" that money, it makes less sense to "waste" money on t-case gearing for the wrong axles then.
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How will it be wrong tcase gearing for the wrong axles when the question was 3.8 or 4.3.
I've ran Toyota duals 2.28/4.7 with numerous combos and honestly only used the ultimate low when showing off or in real bad snow.
Curious more so what the jeep guys have found that work best for them in a 4 speed version. I'm beginning to think the 3.8 for future ideas of a v8.
 
HenikonLJ said:
How will it be wrong tcase gearing for the wrong axles when the question was 3.8 or 4.3.
I've ran Toyota duals 2.28/4.7 with numerous combos and honestly only used the ultimate low when showing off or in real bad snow.
Curious more so what the jeep guys have found that work best for them in a 4 speed version. I'm beginning to think the 3.8 for future ideas of a v8.
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Those 2 are so close it doesn't matter.
 
HenikonLJ said:
How will it be wrong tcase gearing for the wrong axles when the question was 3.8 or 4.3.
I've ran Toyota duals 2.28/4.7 with numerous combos and honestly only used the ultimate low when showing off or in real bad snow.
Curious more so what the jeep guys have found that work best for them in a 4 speed version. I'm beginning to think the 3.8 for future ideas of a v8.
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If you are seriously looking at the 4 speed Atlas, you probably don’t want to be considering the 3.8 or the 4.3 in the case. The four speed is simply a 2.72 planetary in front of a regular Atlas 2 speed. So a 3.8 is going to give you a low of 10.3:1. A 4.3 is going to give you 11.69:1. Neither of those work well in many situations. Put a V8 in front of it, and you will never use those ratios.

I run the 4 speed with a 2.0:1 ratio in the case. That gives me 1:1, 2:1, 2.72:1, and 5.44:1. Those ratios work well for me. It worked well behind the I6, and now behind the Hemi.

Note that I run an auto. Your six speed might work better with the lower ratios.
 
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What you don't seem to get is that you're trying to compensate for extremely inappropriate axle gears with a different TC. And then you say you're replacing your axles but didn't mention what gears you plan to run in them.

Makes it tough to offer useful advice
 
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I would finish your axles first, then determine if you need to change the transfer case.
 
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NashvilleTJ said:
I run the 4 speed with a 2.0:1 ratio in the case. That gives me 1:1, 2:1, 2.72:1, and 5.44:1. Those ratios work well for me.
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I try to explain to folks with autos that if you are going to spend the money on a 4 speed, spend it wisely. Pay for 4 ratios that you can actually use. It makes zero sense to put the Rubicrawler in front of the 231 and wind up with 2 ratios the same. Get something useful for you money, they aren't cheap, don't waste some of your money on duplicate ratios.
 
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mrblaine said:
I try to explain to folks with autos that if you are going to spend the money on a 4 speed, spend it wisely. Pay for 4 ratios that you can actually use. It makes zero sense to put the Rubicrawler in front of the 231 and wind up with 2 ratios the same. Get something useful for you money, they aren't cheap, don't waste some of your money on duplicate ratios.
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I sure am glad you talked me off the ledge...I was pretty close to selling my 4:1 T-case and doing exactly that...But that was all before the auto and based on driving the jeep as a manual. Once the auto was in and I drove it a bit, I realized my idea was silly. Now...I still think something like what Jeff has would be pretty nice, but its not something I feel I need to change right now. With the manual, I was SO sick of 4-low being the only really usuable 4 wheel drive I had.

It cannot be overstated enough how much control a torque converter gives you...so, yes, absolute "crawl ratio" isn't nearly as low as it shows with a manual, but the math doesn't account for the infinitely variable speed of the T/C.
 
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Mike_H said:
I sure am glad you talked me off the ledge...I was pretty close to selling my 4:1 T-case and doing exactly that...But that was all before the auto and based on driving the jeep as a manual. Once the auto was in and I drove it a bit, I realized my idea was silly. Now...I still think something like what Jeff has would be pretty nice, but its not something I feel I need to change right now. With the manual, I was SO sick of 4-low being the only really usuable 4 wheel drive I had.

It cannot be overstated enough how much control a torque converter gives you...so, yes, absolute "crawl ratio" isn't nearly as low as it shows with a manual, but the math doesn't account for the infinitely variable speed of the T/C.
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Not far removed from conversations about brakes. You can tell folks using all the nice words in a dictionary that you can come up with what the differences are and why that matters, but until they actually go drive something with great brakes, you're just wearing out your keyboard. You can explain all day long what the difference is between the rig controlling what you do and you controlling what the rig does and they don't get it until they go do it. Then it is obvious.
 
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g.hayduke said:
What you don't seem to get is that you're trying to compensate for extremely inappropriate axle gears with a different TC. And then you say you're replacing your axles but didn't mention what gears you plan to run in them.

Makes it tough to offer useful advice
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What everyone seems to not understand is that's not the question. I didn't care what my final drive ratio is. I want to know what people have found works best in the jeep world with the 6 speed. Think of the rest of the drivetrain as stock with stock tire sizes for all I care.
I know the deeper gearing will give me more control. I know if I get the deeper gearing and end up swapping to an auto way down the line I'll have new issues like running through the brakes and "less" control. I know those facts but what I don't know is what people have found that works best in the jeep platform the 4.0 is a different powerhouse than I'm used to I don't trust it living on the limiter like my old yotas.
I've ran yota duals behind a 3.4 5speed and was always switching between the 4.7 or 2.28 cases didn't matter if I was on 35s and 4.30 gearing or 40s and 4.10s. different times I needed more gearing options.
 
mrblaine said:
Those 2 are so close it doesn't matter.
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Thanks for being honest 👌 if you where to choose one over the other what would it be? Trying to research and read everyone's opinions about the matter always leads to the same scenario. Either they wish they went deeper or wish the didn't go as deep. Even talking to a few local guys with the 2 speed one guy ended up selling his 4.3 and went to a 5.0 running the 4.0 and ax15 the other guy has a 3.0 gear behind his 5.3 and 4l80 and is looking at adding a underdrive to get a little lower.
Have another guy with a 1uz v8 r150 and 4 speed who has the 3.8 and loves it.
 
HenikonLJ said:
What everyone seems to not understand is that's not the question. I didn't care what my final drive ratio is. I want to know what people have found works best in the jeep world with the 6 speed. Think of the rest of the drivetrain as stock with stock tire sizes for all I care.
I know the deeper gearing will give me more control. I know if I get the deeper gearing and end up swapping to an auto way down the line I'll have new issues like running through the brakes and "less" control. I know those facts but what I don't know is what people have found that works best in the jeep platform the 4.0 is a different powerhouse than I'm used to I don't trust it living on the limiter like my old yotas.
I've ran yota duals behind a 3.4 5speed and was always switching between the 4.7 or 2.28 cases didn't matter if I was on 35s and 4.30 gearing or 40s and 4.10s. different times I needed more gearing options.
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I don't think there is that much experience with a 4 speed atlas on the forum. @NashvilleTJ gave a pretty good answer, and If I were building a 4 speed case, I would end up around those ratios as well. You already know the 4.0:1 is low enough. So, if you put 2.73 in front of that and end up 10.92, do you really see yourself using it? You don't want the 4.0 on the limiter (your words). So, how do you maximize the usefulness? You know the underdrive is going to be 2.73:1. What combined with that gets you around a 4 or 5 to 1? 2.0:1 and 2.73 is 5.46:1. I think that would be the range your looking for. Gives you two more useful ranges AND you go lower yet in your Low, Low range.

If I were to sell my 241, I would look for a rubicrawler and an old NP205. That would give me 2.73:1, 1.9:1, and 5.2:1, behind an auto. That would be a REALLY nice combo. Creepy crawley in the rocks and a couple other ratios to play with when I'm in the sand, mud and snow.
 
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I'm glad this thread is happening because with the auto swap underway and the 4:1 Tera-4 Low I'm not sure what wheeling will be like. My crawl ratio is going from 82:1 to something like 53:1. I'm not too worried about it due to the T/C, but I was already looking at my gearing with a Rubicrawler, but due to the weakness of the Tera 4-Low I'd have to remove it and go with a 231. That would make my ratios 1:1, 2.72:1 and 7.44:1. Nothing in the 3.8-5.5 range. All I'd be getting for $2000 is 7.44:1. Seems like a large waste of money. I concluded it's best to wait and see how it wheels with the auto.

My ideal world is a 241 with a Rubicrawler. Just need to shell out another $4500.
 
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JMT said:
I'm glad this thread is happening because with the auto swap underway and the 4:1 Tera-4 Low I'm not sure what wheeling will be like. My crawl ratio is going from 82:1 to something like 53:1. I'm not too worried about it due to the T/C, but I was already looking at my gearing with a Rubicrawler, but due to the weakness of the Tera 4-Low I'd have to remove it and go with a 231. That would make my ratios 1:1, 2.72:1 and 7.44:1. Nothing in the 3.8-5.5 range. All I'd be getting for $2000 is 7.44:1. Seems like a large waste of money. I concluded it's best to wait and see how it wheels with the auto.

My ideal world is a 241 with a Rubicrawler. Just need to shell out another $4500.
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You know what folks with autos never discuss? That's right, crawl ratio. The auto is far too forgiving and easy to control for that number to even begin to matter. I have never known or cared to know the crawl ratio of a single axle, tire, and gear combo I've had in any of my rigs over the years.

Your ideal world in nowhere near the same planet as mine. I have zero use for 10.88-1 unless someone has given me the task to see how much of their stuff I can break. Then that is a very useful ratio with the auto. The chassis won't even torque over much when you blow up a rear axle.
 
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