R2.8CumminsCJ

Cmath

Scrambler Enthusiast
LIFETIME
CJ-8.com Member
City
Woodstock
State
Ga
#1
I have loved JEEPS since the first time I sat in my dad's 1984 CJ7 and diesels from the first time that I got to drive
one(1,150h.p. monster). So why not combine the two. Now hold on, don't answer that. I know ,they are loud, smokey ,leaky, way to heavy and will rattle themselves apart. But that describes most of the jeeps that I have had anyway. So I have kept my eye out for a decent option that is compatible and maybe could solve some of the problems . So I was thinking that a modern diesel would solve some of the typical issues associated with diesel swaps. At first I thought that the Cummins 5.9 (6BTE I think) but found there is no way to really beat the weight and balance issues. I looked at plenty of options but never really latched on to any. That was until I started seeing info pop up about Cummins working on a modern swap focused complete package, the R2.8 . Fast forward a couple years , a 15% off email and week later a big box is sitting in front of the shop.:headbang:
 

Cmath

Scrambler Enthusiast
LIFETIME
CJ-8.com Member
City
Woodstock
State
Ga
#3
At the moment it is undecided what this is going to go in , the CJ7 or the CJ8. I am leaning towards the CJ7 . I am thinking it is not as heavy as the 8 and should make for pretty fun ride.Either way the plan is
R2.8
6L80e
4.10 gearing
35"tires
 

FLCJ8

Legacy Registered User
City
Palm Bay
State
FL
#5
At the moment it is undecided what this is going to go in , the CJ7 or the CJ8. I am leaning towards the CJ7 . I am thinking it is not as heavy as the 8 and should make for pretty fun ride.Either way the plan is
R2.8
6L80e
4.10 gearing
35"tires
How does the 2.8 compare to the 5.9 as far as optimum RPM?
My '06 MegaCab has 4.10 gears with an auto OD and it's too high (numerically) for efficiently towing a three horse gooseneck at highway speed.

I almost pulled the trigger on this for my 8, but I already have all the parts for a stroker build. Just waiting on a shop.
:popcorn:
 

cdvcj8

It's Not My Scrambler
LIFETIME
CJ-8.com Member
City
West Friendship
State
MD
#6
:popcorn: I was on the waiting list for info for this, but it seems like the support for automatic transmissions is trailing. My vote (of course ) is to put it in the 8!!!
 

certifiablejeep

Definitley Certifiable
LIFETIME
CJ-8.com Member
City
Bedford
State
NH
#7
How does the 2.8 compare to the 5.9 as far as optimum RPM?
My '06 MegaCab has 4.10 gears with an auto OD and it's too high (numerically) for efficiently towing a three horse gooseneck at highway speed.

I almost pulled the trigger on this for my 8, but I already have all the parts for a stroker build. Just waiting on a shop.
:popcorn:
How much does your trailer weight? I have an '05 and when it is loaded up at highway speeds, I am shocked as to how well it does and how great the mileage is... 4.10's as well.
I notice though when the trailer is empty (~2500 lbs.) it gets worse mileage than when it is fully loaded up... odd, but true.

cb
 

93_Fummins

CJ-8 Member
CJ-8.com Member
City
Edmond
State
OK
#8
I'm not going to naysay the R2.8, because I think it's a great project by Cummins exclusively for the swap minded enthusiasts, but I've read that the performance is quite lackluster in "heavier" rigs, JK's being the example. I'd vote for putting in in the CJ-7, as it seems to be a great swap in TJs. The CJ-8 may just open you up to a bit more payload options and begin to reveal the shortcomings of the performance curve, but then again it depends on your desired use of the rig. I've been yearning for a 4BT to put in my CJ-8, but they are more expensive to procure than 6BTs. Anxious to see how this goes, especially with the transmission choice.
 

Shark Bait

CJ-8 Member
CJ-8.com Member
City
Charleston
State
WV
#11
I wanted to go this route for my CK-8 build since I saw it at SEMA in 2016 but in never made it to market into one. I got the email with 15% off Andy bought about buying one and sticking it int the ge corner for the next project but I believe, or hope, their next crate engine will be the 5.0 V-8. At least that's what I heard rumored. Please keep us updated on the build.
:cheers:
 

Cmath

Scrambler Enthusiast
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CJ-8.com Member
City
Woodstock
State
Ga
#12
From what I have gathered optimum torque range 1,500-3,500RPM. They say it will consistently produce around 267lbf. throughout that range.
With the proper gearing/tire combo cruising under 2000RPM. The difference would be full range access to the power rather than waking up at the top of the range . I have an 05' ram with the 5.9 that I tow with and it has 4.10 gears. I love towing with it. Even highway travel I am still surprised how much it takes to really feel like i'm towing something.
 

Cmath

Scrambler Enthusiast
LIFETIME
CJ-8.com Member
City
Woodstock
State
Ga
#13
The 4bt has been on the top of the list for diesel swaps for a while .At least until the 2.8 became an option. The problem is that all of the 4bt rigs I have been in have been almost unbearably loud and shaky . And I love diesel engines. I have talked to some of the people that have been working on the R2.8 and it is said that it is a much smoother running more modern diesel. We will see.
 

Cmath

Scrambler Enthusiast
LIFETIME
CJ-8.com Member
City
Woodstock
State
Ga
#14
I feel pretty good about the transmission choice. The options are kind of limited on the adapter side. There are adapters available for Chevy/GM, Toyota ,LandRover ,Ford, Jeep and maybe some more. If the 6L80e ends up not working out then it is between 4L80e or AX15.

As for the possibility of lack luster performance I am not really worried about that. Ford puts the R2.8 in the F250 in Brazil and that is about the same as the CJ7 and CJ8 combined. I know that the numbers work for the CJ7 And even for stockish CJ8. Adding up all the plans for my 8 put it in the 5,600lb area. If it feels like there will be extra power then the 8 gets one also. If not then the 8 get LS3/6L80/ATLAS.

The 15% off is what ultimately made me pull the trigger. I think it ended up somewhere in the $1,350.00 area for savings. It's the perfect time to buy one and stash it in the shop for a future project. Every one that has something to do with the R2.8 also say that it is likely the 5.0 Cummins is next on the reposer list but it could be a while.

I can't promise a record setting pace with this project like some of you magical Jeep wizards seem to achieve but this should be fun and I will try to post as many pics /info as possible.
 

93_Fummins

CJ-8 Member
CJ-8.com Member
City
Edmond
State
OK
#15
As for the possibility of lack luster performance I am not really worried about that. Ford puts the R2.8 in the F250 in Brazil and that is about the same as the CJ7 and CJ8 combined. I know that the numbers work for the CJ7 And even for stockish CJ8. Adding up all the plans for my 8 put it in the 5,600lb area. If it feels like there will be extra power then the 8 gets one also. If not then the 8 get LS3/6L80/ATLAS.
I am fairly certain that the Brazillian F-250 Cummins is the ISB3.9, not the R2.8....but I could be mistaken.
 

FLCJ8

Legacy Registered User
City
Palm Bay
State
FL
#16
How much does your trailer weight? I have an '05 and when it is loaded up at highway speeds, I am shocked as to how well it does and how great the mileage is... 4.10's as well.
I notice though when the trailer is empty (~2500 lbs.) it gets worse mileage than when it is fully loaded up... odd, but true.

cb
From what I have gathered optimum torque range 1,500-3,500RPM. They say it will consistently produce around 267lbf. throughout that range.
With the proper gearing/tire combo cruising under 2000RPM. The difference would be full range access to the power rather than waking up at the top of the range . I have an 05' ram with the 5.9 that I tow with and it has 4.10 gears. I love towing with it. Even highway travel I am still surprised how much it takes to really feel like i'm towing something.
Yeah, I guess my post wasn't too clear. Need to stop posting at 2AM. :ZZZ: I was referring to fuel economy.
Mine has zero problems towing anything I've put behind it as well.
It just seems to me that I could get by with lower gears and still work out fine, 2000 rpm is about 68 mph.
My 2000 was the same setup except it had an overhead display that would also show instantaneous mpg, and the difference due to the RPM was very noticeable.
Of course most of the miles were in flat FL, GA, & Carolinas.

The 2.8 appears to have a wider optimum torque range than the 5.9
 

Cmath

Scrambler Enthusiast
LIFETIME
CJ-8.com Member
City
Woodstock
State
Ga
#17
The 3.9 was in the earlier Brazilian f250 .Not sure ISF or ISB. 2014 started F250 and F350(Brazilian) R2.8. I have seen it labeled R2.8 and ISF2.8.I am not sure what the differences between the R and ISF are.
 

Cmath

Scrambler Enthusiast
LIFETIME
CJ-8.com Member
City
Woodstock
State
Ga
#18
I can't wait to find out first hand what kind of fuel economy this will get . I read when testing the early prototype swaps in TJs they got low-md 20s trial riding and high 20s on mixed road driving. I will be happy with consistent 20s. The CJ7 with the original 258(rebuilt) at its best is mid teens and the CJ8 with 383stroker is a sad single digits. So i will be easily impressed .
 

tower210

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Olathe
State
KS
#19
I can't wait to find out first hand what kind of fuel economy this will get . I read when testing the early prototype swaps in TJs they got low-md 20s trial riding and high 20s on mixed road driving. I will be happy with consistent 20s. The CJ7 with the original 258(rebuilt) at its best is mid teens and the CJ8 with 383stroker is a sad single digits. So i will be easily impressed .
This AWESOME!!! :bacon: :bacon:

I didn't think the price for a brand new crate motor was bad when these came out (most of the packaged gm and ford crates are 12-13k; none are diesel). 15% off had to put it as just over 8k; that seems like a steal if you are considering new crates.

I'd put it in whatever you drive most. Seems like that is the best way to take advantage of new diesel engineering and reliability!! :headbang:

Does it require DEF?
 

MrBeep

CJ-8 Vendor Supporter
CJ-8.com Vendor
City
Dillsboro
State
IN
#20
This thread will be watched with lots of interest. Diesel power and economy are hard to beat. :wave:
 
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