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Old 06-21-2014, 06:19 PM   #1
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Talking Diesel swap

So I have always wanted a 4bt diesel jeep and want to know what I need I'm in the process of installing a 4.5" lift now. My buddy also has a liquid cooled 4 cylinder duetz motor that I was considering to put in cause the price of a 4bt . Will the stock axles be alright not going with a crazy tire size probably staying around 33s and how do you do the fuel system, have a ax15 already for the swap

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Old 06-24-2014, 02:44 PM   #2
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The biggest thing about a 4bt swap is cost. A buddy of mine has well over 10K into his and he isn't even completed yet.

The stock axles wont work for a diesel swap. The diesel produces too much torque for either axle to handle. Even with 33's on them. 1st time you want to romp on it, something will break. Guaranteed. Doesn't matter if it's the 4bt or the duetz motor.

You need much heavier axles to handle the torque of a diesel. Dana 60 or 70 or a 14 bolt, Something that was designed to handle the torque.

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Old 06-24-2014, 11:26 PM   #3
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found one for 2500 don't have the funds to get it yet but its turbod intercooled. what about an 8.8 rear end, hopefully i don't have to spend 10k got the lift kit for it already
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Old 06-25-2014, 02:21 PM   #4
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I have an 8.8 in mine, and I love the axle. But I wouldn't go with anything less that 1 ton running gear if I had a diesel power plant. The 8.8 would be a 5 times better axle than stock, but all in all, it isn't going to handle the torque any better. On the street it would be fine. Out in the woods where you need it to perform, all it would take is 1 spot of pure traction, and a deep stomp on the skinny pedal, let the black smoke roll, and listen to the snapping of metal parts!...lol.

Your engine now produces around something like 80lbs of torque, and the diesel is 6 or 7 times that. So you need drivetrain that can handle 6-7 times more than you can give it now. Just to be in the safe zone. Even the strongest axle can still break under certain circumstances.
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Old 06-25-2014, 10:39 PM   #5
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ok so bigger then an 8.8 and was just gonna stick with the same gears its like 3.73 right? for the fuel system what do you do with that and a clutch do you run with the ax15? a buddy of mine did a t case upgrade for his v8 swap but doesn't remember where he got it or the name
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Old 06-26-2014, 07:07 AM   #6
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If its a manual now, it has 4.10's in it for a gear ratio. And the manual trans behind a 2.5 is an AX5, not an AX15. They are found in the 4.0L YJ's.

As far as fuel delivery, you can use the same tank, and just use an electric inline fuel pump.

As far as clutch, the pressure plate will need to be made for the 4BT flywheel, and then get a clutch disc to match the spline count on the input shaft of the AX 15. Getting a bell housing to match between the 2 will be your biggest obstacle.
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Old 06-26-2014, 08:45 PM   #7
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It has the ax5 now I bought a ax15 from a buddy who blew his 4.0 up. So won't have to do new fuel lines? Can I use the fuel pump in the tank and have a inline pump?
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Old 06-26-2014, 08:47 PM   #8
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There Is a site that I was reading if you get a 4bt with the ford trans keep the bell housing and get an adapter for the ford bell housing to the ax15
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Old 07-02-2014, 11:50 AM   #9
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If you decide to go 4bt the 3.73 gears with 33s produce the best fuel economy. When I do mine I plan on keeping my 4.10 and 35s. I'm still in the early planning stages of mine.
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Old 07-03-2014, 10:12 PM   #10
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I'm still in the process of getting a motor jeep funds are tight at the moment ditched the duetz idea parts would be a pain to find if out of state and it's only pushing 94 hp would be like putting my 2.5 back in it lol
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Old 07-04-2014, 07:58 AM   #11
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What's the true advantage of swapping the 4bt. Compared to the amc 4.2 the hp and torque isn't a drastic increase for a naturally aspirated 4bt.
But I do understand the "holy crap a diesel jeep!" aspect.
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Old 07-31-2014, 11:48 AM   #12
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whoa.... ok lets get some things straight....

First, the AX-15 is probably not the best thing to put behind a 4BT, not to mention it is a pain in the ass to do so, but I do believe the ford bellhousing idea does work, but I have no idea what you would do for a clutch at that point. I always recommend pulling an NV4500 from a 6BT dodge ram, including bellhousing, clutch, adapter plate, ect, everything will bolt straight to a 4BT, and it is a super tough trans. You can get an adapter from AA to mate the NP231 t-case to the NV4500 and you are done.

Fuel Delivery, same tank, same lines, but you have to drop the tank, pull the electric pump and install a dip tube. There is a mechanical lift pump on the 4BT, you do not need an electric fuel pump at all.

I agree, the 8.8 is probably not the best axle, but it is much better than the D35, and an easy/cheap upgrade.

I would not agree that 3.73s on 33" tires will get the best fuel economy, this engine redlines at 2800 rpm, you want cruising rpms to be around 2000, this all depends on what speed you consider cruising though.

why would you ever consider a naturally aspirated 4B..... that would actually be a 4B..... since the the "T" in 4BT is for "turbo"....

The 4BT can produce tons of power reliably without a whole lot of modification.

if you need motor mounts, check out this place.

Jeep-Motor-Mounts
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Old 07-31-2014, 12:24 PM   #13
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Sweet. I've been looking for some good motor mounts

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