Alright, so I've gone almost completely down the rabbit hole with jeep mods. While I'm waiting on hardware for the dana 60 to come in, I decided to look at cases, only to give myself more of a headache. My question is, with a 4bt and 3/4 ton setup, 4.56 axle gearing, should I get a Rubicon transfer case, or stronger np231/ stock "gearing"
Transfer case rabbit hole
- Thread starter Revenant4x4
- Start date
There are forum members more experienced than I am, but in the XJs where owners do 4.6L strokers or V8 conversions there are members that have upgraded to the TeraLow (heard they are no longer available for the NP231 unless there is still NOS). A NP241OR is certainly a lot stronger than the NP231J, but whether it's capable of handling the torque of the 4BT; I do not know.
Then there others that have upgraded further to the Atlas TC of which there are numerous ratios available.
You may need to get an adapter plate to bolt up the Atlas to what ever transmission you are using.
The forum member who certainly would know the answers to your questions would be Mr. Blaine.
Then there others that have upgraded further to the Atlas TC of which there are numerous ratios available.
You may need to get an adapter plate to bolt up the Atlas to what ever transmission you are using.
The forum member who certainly would know the answers to your questions would be Mr. Blaine.
For the price of a 241, for about a grand more you can get an atlas. My personal opinion; its an easy choice if tons and motor swap are already part of the equation.
I thought about the atlas, but I still want this jeep tik be decent on the road. Would the atlas gear me down too low?
The high speed of the transfer case would be 1:1, so the only thing that would make it unbearable on the road would be the wrong rear gear choice. Depending on which Atlas you go with, you can tailor your low transfer case range, based on your wheeling needs. For example:
With the 2 Speed Atlas you get 1:1 (High) and a choice of Low Range: 1.5:1 or 2.0:1 or 3.0:1 or 3.8:1 or 4.3:1 or 5.0:1.
The 4 Speed ratios look like this:
1.0:1 / 2.72:1 / 1.50:1 / 4.08:1
1.0:1 / 2.72:1 / 2.00:1 / 5.44:1
1.0:1 / 2.72:1 / 3.00:1 / 8.16:1
1.0:1 / 2.72:1 / 3.80:1 / 10.34:1
1.0:1 / 2.72:1 / 4.3:1 / 11.69:1
I've got the R2.8 Cummins (stock tune) and have been driving it almost daily for over a year, I wouldn't really worry about your T-case strength for a mildly tuned 4BT, but I feel like the Rubicon Tcase costs too much ($2K+ when I've seen them) and I want more than 4:1. Driving style does matter. If you're playing bumper cars and very dynamic, then I wouldn't go lower, but IMO that's not where diesel shines. I would only want my diesel stuff to go through stuff very slow and at the end of the day have twice as much fuel left in the tank as everyone and have less dings by idling through obstacles. There's many more benefits, but those are major benefits.
I would love the Atlas 4, but I'm afraid that without stretching my frame, that I can't get all the clearance I want with such a long setup, even with GPS so I can eliminate the Speedo. I'm gonna go with the Atlas 2 and try to beg for the 6:1, but may settle for the 5:1 and if that's not enough then I'm gonna swap the AX-15 out for TR-4050 with a 1st gear around 6:1.
What tire size are you running? Are you running the NV4500? A good 3/4 ton transmission would be a nice addition and in that case I wouldn't worry about less than 4:1 for a t-case, but I'd still want it. My NV4500, 3.73s and 2.72 Tcase in my truck is a very nice compliment to 33s. I'm lazy and risk adverse, so if I could go slower in my gearing though then I'd do it, unless it's super annoying on the highway, which is why I don't like getting too fancy in the axles.
What mods have been done to the 4BT? If it's stock, in some cases they aren't too crazy, but it depends on how much fuel you're getting to it and your turbo setup. I do really like the additional displacement of the 4BT. I always like more displacement on diesel, but I opted for the 2.8 because of the size and ease with the common rail. However 4BTs are very cool in my book, but still behind the 6BT which is the holy grail engine IMO. Just more engine than I'd want in a Jeep.
I would love the Atlas 4, but I'm afraid that without stretching my frame, that I can't get all the clearance I want with such a long setup, even with GPS so I can eliminate the Speedo. I'm gonna go with the Atlas 2 and try to beg for the 6:1, but may settle for the 5:1 and if that's not enough then I'm gonna swap the AX-15 out for TR-4050 with a 1st gear around 6:1.
What tire size are you running? Are you running the NV4500? A good 3/4 ton transmission would be a nice addition and in that case I wouldn't worry about less than 4:1 for a t-case, but I'd still want it. My NV4500, 3.73s and 2.72 Tcase in my truck is a very nice compliment to 33s. I'm lazy and risk adverse, so if I could go slower in my gearing though then I'd do it, unless it's super annoying on the highway, which is why I don't like getting too fancy in the axles.
What mods have been done to the 4BT? If it's stock, in some cases they aren't too crazy, but it depends on how much fuel you're getting to it and your turbo setup. I do really like the additional displacement of the 4BT. I always like more displacement on diesel, but I opted for the 2.8 because of the size and ease with the common rail. However 4BTs are very cool in my book, but still behind the 6BT which is the holy grail engine IMO. Just more engine than I'd want in a Jeep.
Oh and the Atlas T-cases have a 2Lo, which is really cool for a few situations, but mostly towing on hills and stuff. If you've got a 3/4 ton transmission this isn't an issue though.
This is a lot of information that I needed, thank you. I'm currently building the 3/4 ton axles from almost scratch, then from there I need custom driveshafts.
As for transmission I'm keeping the ax15, just going for the terminator upgrade. I've decided I'm going to try and go with the 4 speed atlas tcase, if itll fit with the Dana 60 rear and 4inch lift without extending wheelbase.
Lastly I dont have the diesel yet, I'm torn between the 3.9 cummins or the r2.8. R2.8 would be lighter and better fuel economy but the 3.9 4BT is cheaper, easier to add power and almost completely mechanical so the mud and water wouldn't be as much of a problem.
So basically, I'm torn between atlas 2 speed or 4 speed, and r2.8 or 4bt 3.9. I want about 400-500ft lbs of torque from the engine.
Also I'm pretty sure atlas 4 speed without speedometer is 1in shorter than stock np231 in my tj
As for transmission I'm keeping the ax15, just going for the terminator upgrade. I've decided I'm going to try and go with the 4 speed atlas tcase, if itll fit with the Dana 60 rear and 4inch lift without extending wheelbase.
Lastly I dont have the diesel yet, I'm torn between the 3.9 cummins or the r2.8. R2.8 would be lighter and better fuel economy but the 3.9 4BT is cheaper, easier to add power and almost completely mechanical so the mud and water wouldn't be as much of a problem.
So basically, I'm torn between atlas 2 speed or 4 speed, and r2.8 or 4bt 3.9. I want about 400-500ft lbs of torque from the engine.
Also I'm pretty sure atlas 4 speed without speedometer is 1in shorter than stock np231 in my tj
Terminator upgrade? I need more information because my AX-15 is old. I really really want an AX-15 with a 4.3 or 5.15 Toyota first gear, but I can't seem to find much info on how to do that.
The problem without extending the wheelbase is that your rear driveshaft angle is going to be an issue pretty quickly. People already shorten up the NP231 with tiny slip yoke eliminators to handle many of the 3+ in lifts, especially with a tummy tuck, which I want. If you have found otherwise, I'm all ears, because I really want an Atlas 4. On top of that angle issue, you may need a bigger U-joint, which will give the rear driveshaft less flexibility.
However, you're doing an engine swap. MOVE EVERYTHING FORWARD. And if you move it forward, I would think very heavily about the R2.8, but it's gonna be tight. You will definitely have to relocate the DOC and the oil pan may be an issue, but maybe you can move it forward an inch and then with adjustable control arms, push your rear axle back an inch or 2 for some really nice clearance when you're finished. I thought I've read that when guys start running 37s or more that they tend to do a stretch.
On my YJ build (hopefully it'll happen this decade), I'm already planning to stretch it several inches, but I'm gonna go with a doubler 231/300 and I'm planning a TR-4050 or I've seen some lighter NV4500s.
As far as the 4BT being cheaper, they certainly used to be and from what I could tell was that I could get one for $4k. Then to rebuild and upgrade it, I'd be around $4k or more. The p-pump, if you could get the one everyone likes is a pricey injection pump on top of that, so you could easily be in that engine, depending on what you can find and who you can get to work on it and their pricing for more than a R2.8, all said and done. R2.8 is about $8k out the door. Installation is a problem with either, but kits are very pricey for either.
I think the 4BT is more rugged and would handle the 400 ft lbs better than the R2.8, but to get there you're gonna have a lot of money in the 4BT, if you are paying people. The R2.8 can be turned up to 400 ft lbs just by a quick tune (EFI Live is $1,300 or a mild tune runs about $1k), but I'm not sure it's proven reliable at that point on anything that's had more than a handful of miles on it and that is very dependent on how hard someone is on it. Now down the line there's talk of an aftermarket crankshaft to stroke the 2.8, which would be very cool to see it at around 3.2L and with a built bottom end your guess is as good as mine what all it could handle. Bottom end is fairly light duty on the R2.8 from what I've heard, so eventhough you can tune above 200 hp and over 400 ft lbs, I wouldn't trust it for something I want to get 250k miles out of.
The problem without extending the wheelbase is that your rear driveshaft angle is going to be an issue pretty quickly. People already shorten up the NP231 with tiny slip yoke eliminators to handle many of the 3+ in lifts, especially with a tummy tuck, which I want. If you have found otherwise, I'm all ears, because I really want an Atlas 4. On top of that angle issue, you may need a bigger U-joint, which will give the rear driveshaft less flexibility.
However, you're doing an engine swap. MOVE EVERYTHING FORWARD. And if you move it forward, I would think very heavily about the R2.8, but it's gonna be tight. You will definitely have to relocate the DOC and the oil pan may be an issue, but maybe you can move it forward an inch and then with adjustable control arms, push your rear axle back an inch or 2 for some really nice clearance when you're finished. I thought I've read that when guys start running 37s or more that they tend to do a stretch.
On my YJ build (hopefully it'll happen this decade), I'm already planning to stretch it several inches, but I'm gonna go with a doubler 231/300 and I'm planning a TR-4050 or I've seen some lighter NV4500s.
As far as the 4BT being cheaper, they certainly used to be and from what I could tell was that I could get one for $4k. Then to rebuild and upgrade it, I'd be around $4k or more. The p-pump, if you could get the one everyone likes is a pricey injection pump on top of that, so you could easily be in that engine, depending on what you can find and who you can get to work on it and their pricing for more than a R2.8, all said and done. R2.8 is about $8k out the door. Installation is a problem with either, but kits are very pricey for either.
I think the 4BT is more rugged and would handle the 400 ft lbs better than the R2.8, but to get there you're gonna have a lot of money in the 4BT, if you are paying people. The R2.8 can be turned up to 400 ft lbs just by a quick tune (EFI Live is $1,300 or a mild tune runs about $1k), but I'm not sure it's proven reliable at that point on anything that's had more than a handful of miles on it and that is very dependent on how hard someone is on it. Now down the line there's talk of an aftermarket crankshaft to stroke the 2.8, which would be very cool to see it at around 3.2L and with a built bottom end your guess is as good as mine what all it could handle. Bottom end is fairly light duty on the R2.8 from what I've heard, so eventhough you can tune above 200 hp and over 400 ft lbs, I wouldn't trust it for something I want to get 250k miles out of.
RSGear makes the terminator, its basically a bulletproof ax15 for around 1700 new. And look at bleepinjeep's video for the install of the 4 speed atlas, it's about the same size, maybe an inch shorter without the speedo. If I get more information on the r2.8 with power capabilities I'll probably do that, but I do all my own work, so either one I'd save money with labor cost. I just think the 4bt would be better for my needs. Would be really badass to have either diesel, as long as it's a cummins imo. The engine is the last thing I'm upgrading, so I have more time to research. Just starting to look now so I get all questions answered and do my homework before jumping headfirst into a swap
I'm was thinking the Bleepinjeep is now Dirt lifestyle and I thought he stretched his Jeep. I hope RSGear still makes that AX-15. That's gonna happen pretty soon if they do. I keep wanting to find out how to do the Toyota gears in it too. I kinda know what is needed, but kinda isn't enough and the specific Toyota transmissions are rare and likely discontinued. Marlincrawler used to offer a beefed up AX-15. I might see what they think their version can handle.
Btw, I saw some stuff on the terminator, 1 place said 485 ft lbs and another 385 ft lbs. Either would be fine for me, but if you're looking to really get some torque out then I'd clarify.
I'll try to catch more of the Youtube stuff to see what's out there and send some emails.
Btw, I saw some stuff on the terminator, 1 place said 485 ft lbs and another 385 ft lbs. Either would be fine for me, but if you're looking to really get some torque out then I'd clarify.
I'll try to catch more of the Youtube stuff to see what's out there and send some emails.
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