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Old 06-04-2018, 10:13 PM
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Just got my YJ back and I want to do a 4BT Cummins swap

Hey all, I am new here and I just got my 93 YJ back after being stolen 4 years ago. Luckily it is still in good shape except for the transmission was removed at some point, but the transfer case and drive shafts are still there. Anyway, down to basics, it is a 1993 Jeep YJ with a 2.5l 4 cyl engine and it was an automatic with 31" tires and a 3" BDS suspension lift. I am going to put a Ford 8.8" rear end in it. What year and model of 4BT Cummins do I want to get for this thing? Do I start junkyard diving or should I break the bank and get a crate motor? What transmission? Please keep in mind I would like an overdrive transmission. I am not going to hotrod this motor but it will be warmed over. I am fresh from the drag racing world, I lost my racing licence on a medical and I need another project, and this is it. Any suggestions would be very appreciated.

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Old 06-04-2018, 11:09 PM   #2
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The Ford 8.8 is a good option for what you're looking to do. However, the 4BT has some considerations and coming from the drag/high-HP world, you're gonna feel like you're driving a tractor by comparison. I'm not a huge 4BT fan (a R2.8 on the other hand!) and with your experience and knowledge, a EFI V8 swap sounds like a great option.

A bigger question that remains unanswered - what do you intend to do with the Jeep, wheel it or mostly drive on the streets? What type of wheeling do you enjoy? Also, where do you live? A 4BT may not be emissions legal for transplanting (non-light duty to light duty is typically no-no by EPA/DEQ standards).
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Old 06-04-2018, 11:35 PM   #3
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I've heard good things about the OM617? Diesel I think it's called?
But I don't have any first hand experience with it vs other diesels.
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Old 06-05-2018, 12:23 AM   #4
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Here is a link to an interesting video of putting the Cummins crate engine in a TJ. You would face a similar situation with a YJ.

Until Jeep put the 42RE automatic in the TJ, no automatic had overdrive. I had a '93 (bought new) with the automatic and it seemed like I was stopping every 100 miles for gas. To put the overdrive transmission in the Jeep you would have to have the computer to go with it. You might be better off with the AX-15 manual (which btw is still in production).

https://www.youtube.com/watch?v=I6H5dM-hxdU
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Old 06-05-2018, 12:31 AM
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I am in Alberta, Canada, most of my wheeling is in the Rocky Mountains in Southern Alberta, mostly shale covered mountains, mud, water holes ect. We go out there with the ATV's and my RZR several times a year and my YJ out there all the time before it was stolen. I had I do drive it on the streets in the winter, but I also have my pick up and the wifes SUV. I have never had an emissions check on anything and I have had some pretty rank street rods. The whole point of this build is to have something that is usable, but also to build something different than a gas/alcohol 3000 hp monster that I have to tear down after a 5.7 second run. Diesels don't bother me, I have worked in the oilpatch all over the world for the last 35 years. I have had more than 10 diesel pickups, my motorhome is a pre emission C12 Cat ect, ect.

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Old 06-05-2018, 01:42 AM
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Originally Posted by rgreen65 View Post
Here is a link to an interesting video of putting the Cummins crate engine in a TJ. You would face a similar situation with a YJ.

Until Jeep put the 42RE automatic in the TJ, no automatic had overdrive. I had a '93 (bought new) with the automatic and it seemed like I was stopping every 100 miles for gas. To put the overdrive transmission in the Jeep you would have to have the computer to go with it. You might be better off with the AX-15 manual (which btw is still in production).

http://www.youtube.com/watch?v=I6H5dM-hxdU
Will the AX-15 handle the torque these little diesels put out? That was a good video, thanks
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Old 06-05-2018, 01:53 AM
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Originally Posted by pc1p View Post
The Ford 8.8 is a good option for what you're looking to do. However, the 4BT has some considerations and coming from the drag/high-HP world, you're gonna feel like you're driving a tractor by comparison. I'm not a huge 4BT fan (a R2.8 on the other hand!) and with your experience and knowledge, a EFI V8 swap sounds like a great option.

A bigger question that remains unanswered - what do you intend to do with the Jeep, wheel it or mostly drive on the streets? What type of wheeling do you enjoy? Also, where do you live? A 4BT may not be emissions legal for transplanting (non-light duty to light duty is typically no-no by EPA/DEQ standards).
I have been doing a lot of reading about the R2.8 and that seems like a nice little engine. I will be looking at that as an option for sure. Thanks for the tip!
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Old 06-05-2018, 09:44 AM   #8
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Old bread trucks (P vans) were retrofitted with 4BT's, and they're probably the most common source for donor engines.

The 4BT is a good bit heavier than the 2.5l you have now, and a bit heavier than a 4.0l (~100lbs more).

Known issue is vertical clearance, especially under-vehicle. These engines are pretty tall. Your 3" lift *should* be enough.

They're stupid simple, though. They make peak torque around 100 rpm's off idle, and stay near peak torque til close to 2000, commonly referred to as a torque wall lol.

I say go for it if you want. I have one I was gonna put in my 1987 YJ, but I virtually had a 5.3l fall in my lap (got stuck with it after picking it up for a friend in need), so I'm using that instead. But, I'll use the Cummins in a J10 or Wagoneer project in the future.

If you gear right for the engine/torque range, they get excellent fuel mileage and operate well on and off road.

Definitely put up a build thread when you get started!
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Old 06-05-2018, 10:07 AM   #9
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How does the 4bt & om617 Mercedes diesel compare?
I have a 6bt in my dodge truck & it's a great motor. So I'm assuming the 4bt is equally good.
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Old 06-05-2018, 02:39 PM   #10
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Generally speaking, the OM617 is more "civilized" and street friendly. Parts are also more easily available.

The 4BT is more parts limited, is heavier, noisier and less refined for daily use. That being said, the 4BT has a good track record for squeezing more performance out of it.

Here's a link I have saved in my "Diesel Options" folder

https://forum.ih8mud.com/threads/4bt-vs-om617.766894/
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Old 06-05-2018, 03:15 PM   #11
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Generally speaking, the OM617 is more "civilized" and street friendly. Parts are also more easily available.

The 4BT is more parts limited, is heavier, noisier and less refined for daily use. That being said, the 4BT has a good track record for squeezing more performance out of it.

Here's a link I have saved in my "Diesel Options" folder

https://forum.ih8mud.com/threads/4bt-vs-om617.766894/
Damn I was thinking a v8 swap for mine, but now that om617 is looking pretty appealing!
Great link thanks
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Old 06-05-2018, 03:59 PM
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The more I read about this Cummins R2.8 the more I like it, and I am pretty sure I will go with one of these, barring any major issues they have that I haven't read about yet. My questions are will an AX-15 manual transmission and a New Process 231 handle the HP and torque this engine puts out (161hp @360 0 rpm and 267 lb-ft tq @1500-3000 RPM)? Rear axle will be a ford 8.8 out of a Ford Explorer with a locker and the front a D30 with a locker gears will be 3.73 running between a 31" and a 35" tire. Will this driveline hold up to this setup or will it fold the first time I put pressure on it?

https://www.kijiji.ca/v-engines-and-...ine/1352099881

I just found this on Kijiji 4 hrs north of me, may have to go on a road trip next week and grab this
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Old 06-05-2018, 04:15 PM   #13
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Sorry to jack your thread Bear.
(But anyone else thinking om617)
I just saw this;
25 land speed & endurance records, I'm impressed....
The turbo om617 seems the way to go, to me
https://en.m.wikipedia.org/wiki/Mercedes-Benz_OM617
Wiki has a great page on where to source om617's & break downs of each variant.
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Old 06-05-2018, 04:31 PM
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No worries, all information is good
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Old 06-05-2018, 05:06 PM   #15
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The more I read about this Cummins R2.8 the more I like it, and I am pretty sure I will go with one of these, barring any major issues they have that I haven't read about yet. My questions are will an AX-15 manual transmission and a New Process 231 handle the HP and torque this engine puts out (161hp @360 0 rpm and 267 lb-ft tq @1500-3000 RPM)? Rear axle will be a ford 8.8 out of a Ford Explorer with a locker and the front a D30 with a locker gears will be 3.73 running between a 31" and a 35" tire. Will this driveline hold up to this setup or will it fold the first time I put pressure on it?

https://www.kijiji.ca/v-engines-and-...ine/1352099881

I just found this on Kijiji 4 hrs north of me, may have to go on a road trip next week and grab this
The R2.8 is cool but the ~$9k price tag is hard to justify... With any luck, it will come down in $$ over the next few years.

The AX15 and NP231 should handle that power easily as it is close to 4.0L power output.

Depending on what tire size you end up with, you may want a bit more gearing for a better crawl ratio and slower crawl speed.
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Old 06-05-2018, 07:02 PM
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That $9K turns into a $12K price tag up here in Canazuela (the new Venezuela), but it is what it is, it is one way of getting a new engine, not one I have to dig into and rebuild, or find it needs a new rotating assembly ect, ect. I love driving this Jeep and think it would be my daily driver locally as well as playing out in the mountains. Hell I think I would even put an AC unit in it because I am old and can only take the heat so much now days. I just sold my race car, I still need to sell a bunch of spares and other racing equipment, so it is time for a toy that gives me something to work on and I can enjoy running it as well. This is me with my old hobby

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Old 06-06-2018, 09:59 AM   #17
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The Ram 6BT was a crazy ideal that the Chrysler engineers had to compete with the normally aspirated Chevy diesel which had power and got good fuel economy but was slow. They went to Cummins and got a commitment to get a limited number of 6B short blocks, IIRC it was only 30,000 per year initially. Chrysler designed and produced the head which was configured for turbocharging hence the 6BT.


For those interested in the 4BT, here's a video from Jay Leno's garage you might enjoy.
https://www.youtube.com/watch?v=0c68L_tieVs
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Old 06-06-2018, 10:46 AM   #18
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I don't know what the power potential of the R2.8 will be. It was designed to meet CARB and EPA standards so it could be installed legally in light-duty vehicles. It seems efficiency was their intended goal and I haven't heard anything, even from Cummins, about what this bad boy would be able to achieve.

The 4BT on the other hand can be something serious! It has a few known power "steps" and can be mild to wild, good for a former drag car tuner who likes to tinker The only issue is again parts availability. You'll want to stock spares of a number of known failure points (not that there's many, but the ones that are have a lead time).
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Old 06-06-2018, 04:00 PM
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The problem with going with a 4BT would be me lol. I have a hard time stopping at "some" modification LOL. I know within a few years that thing would be turned up as far as I could make it, I would be breaking transmissions, Tcases, u joints, driveshafts ect. and I would be spending big dollars building the whole thing to hold up and it would end up very unstreetable. I have been down this road before and it was a lot of fun, but it turned into a lot of work, and a lot of money and I spent more time pulling wrenches than racing. If I go with the R2.8 I get a project to keep me busy and then I get a good reliable Jeep with more than enough power to do what I want it to do going down the street/highway or out wheeling in the mountains. This is why I am going with the R2.8.
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Old 06-06-2018, 04:31 PM
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I just started a new thread on the R2.8 Repower

https://www.wranglerforum.com/f290/cu...r-2307066.html
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Old 06-06-2018, 05:46 PM   #21
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The problem with going with a 4BT would be me lol. I have a hard time stopping at "some" modification LOL. I know within a few years that thing would be turned up as far as I could make it, I would be breaking transmissions, Tcases, u joints, driveshafts ect. and I would be spending big dollars building the whole thing to hold up and it would end up very unstreetable. I have been down this road before and it was a lot of fun, but it turned into a lot of work, and a lot of money and I spent more time pulling wrenches than racing. If I go with the R2.8 I get a project to keep me busy and then I get a good reliable Jeep with more than enough power to do what I want it to do going down the street/highway or out wheeling in the mountains. This is why I am going with the R2.8.
This is exactly why I'm building a stroker and not doing an LS swap

Looking forward to seeing your project come along!
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Old 06-07-2018, 08:28 AM   #22
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Generally speaking, the OM617 is more "civilized" and street friendly. Parts are also more easily available.

The 4BT is more parts limited, is heavier, noisier and less refined for daily use. That being said, the 4BT has a good track record for squeezing more performance out of it.

Here's a link I have saved in my "Diesel Options" folder <img src="https://www.wranglerforum.com/images/smilies/smile.gif" border="0" alt="" title="Smile" class="inlineimg" />

https://forum.ih8mud.com/threads/4bt-vs-om617.766894/
The 4BT is basically a 6BT, minus 2 cylinders. Same pistons, valves, etc. Which means parts are pretty abundant. There are way more 6BT's available than 4BT's, though, so the initial cost for the engine can be much higher than the 6.
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Old 06-07-2018, 12:38 PM   #23
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The 4BT is basically a 6BT, minus 2 cylinders. Same pistons, valves, etc. Which means parts are pretty abundant. There are way more 6BT's available than 4BT's, though, so the initial cost for the engine can be much higher than the 6.
The 4BT remains a common swap here in AZ - the #1 complaint I hear is that parts are hard to come by locally. Now it could simply be the local market or lack of popularity compared to other regions. That being said, I should clarify that when I said parts are "limited" I meant as in going to the store or local shop to get something. If you're wheeling and something breaks on a 4BT, you better have a spare, get lucky on Amazon Prime 1-day, or find a good tow company. When compared to something like an LS engine or even the OM617, the parts availability is indeed limited (again, referring to locals and people within the SW region who run 4BTs).

With the interwebs, parts are easily sourced, which I think is why the Paint Shaker remains popular. That being said, the internet is a blessing and a curse for the 4BT and older Jeeps in general. The popularity of "hub" stores and 2-day shipping is making more and more part stores stock less and less.

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