Another Cummins swap

For everything related to converting and up keeping diesel engines in an FSJ
Post Reply

Topic author
boomersrule55
Posts: 6
Joined: Fri Dec 24, 2021 10:17 pm

Another Cummins swap

Post by boomersrule55 » Fri Dec 24, 2021 10:48 pm

Hey everyone, I am currently looking into a 4BT or Cummins 2.8 swap for my 88 GW, though I am leaning towards the 4BT because I have two 12V's, one in a 95 4x4 dodge and the other in a 96 Winnebago pusher, so I have experience working on these motors. I would like to run a 4L60, 4L60e or 700R4 with a matching TC to avoid adapting to the stock GW TC, any advise on this? or how about running a 47RH with NP 241DLD behind the 4BT will it Fit? I was going to crawl under my 95 and measure it out... just want to know if anyone has tried these swaps, thanks


scout4bta
Posts: 2
Joined: Sat Jul 21, 2018 10:45 am
Location: Willcox AZ

Re: Another Cummins swap

Post by scout4bta » Sat Dec 25, 2021 3:54 pm

I'm currently doing a 4BT swap into my 89 GW, using a 46RH (non lockup) from a first gen Dodge Diesel and a Atlas T-case.
I would advise against the 4L60's or the 700R4, these don't have good record of holding up behind the 4BT torque. The 47RH will work as long as it came from a behind a Diesel. The NP241DLD is a "light duty t-case, used on gas motors, Use a NP241DHD from a Diesel application.
1989 GW, Dieselize in progress


Topic author
boomersrule55
Posts: 6
Joined: Fri Dec 24, 2021 10:17 pm

Re: Another Cummins swap

Post by boomersrule55 » Sat Dec 25, 2021 8:35 pm

Got it thanks, sounds like a 47RH will fit my swap, however I am pretty sure I have a NP241DLD behind my 95 12v, at least that's what the spec tag said when I last checked the oil and doing calcs to put a Allison 1000 in my 2500, which I abandoned and sold the Allison...anyways I was hoping to mate a 4BT to the 47RH and a TC without running thru adapters... I will crawl under my 2nd gen and check overall the length of 47RH and TC, thanks for the help.


scout4bta
Posts: 2
Joined: Sat Jul 21, 2018 10:45 am
Location: Willcox AZ

Re: Another Cummins swap

Post by scout4bta » Thu Dec 30, 2021 12:24 pm

All you need to mate the 4BT to the 47RH is a trans adapter from a 94-98 Dodge Diesel, there may be later years that will work.
My 46RH is approximately 31 7/16" long. The Lockup TC will add about another 1" or more.
1989 GW, Dieselize in progress


Topic author
boomersrule55
Posts: 6
Joined: Fri Dec 24, 2021 10:17 pm

Re: Another Cummins swap

Post by boomersrule55 » Fri Dec 31, 2021 2:35 pm

Ok thanks, however I am thinking of now trying to find a complete 94-95 6BT automatic 4x4 drive train, which I happen to own but I am not willing to sacrifice for this project, I will be able to crawl under there and do some math which will help. I see others have put 6BT's in FSJ's just worried about the weight and such. I have a rough country 3" lift in my shop that will be going in and will probably have to box the frame and add extra spring loading. The prices they want for a 4BT is way out there and I am not sure about the R2.8 and that rear cam drive or ohc diesels overall, even though I own a 2018 6.7 4x4 which has been a great truck so far with only 18k on the clock it's probably to soon to tell, so I will start researching a 6BT swap on this and other sites to see all involved.

User avatar

Pablo
Posts: 148
Joined: Sun Dec 15, 2013 6:58 pm
Location: Arizona

Re: Another Cummins swap

Post by Pablo » Sat Jan 08, 2022 4:43 pm

4bt's came with more than one bellhousing. What you can put behind one depends on the bellhousing you have. You can swap them. Some bellhousing are darn near unobtainable used.

I would not pay the current 4bt prices. I would look at Isuzu's in the 3.9 range from NPR trucks or investigate Cummin's newer 3.9 ISB series. Perhaps buy a whole vehicle and part it out to make your money back.

The Cummins 2.8 I hear nothing but good things, but in my opinion it is a tad bit too undersized for this application at stock power levels. I had a 2.8 sized crappy Italian diesel in a Jeep Liberty. That engine was rated at almost the same power levels stock as the Cummins 2.8, so rough power expectations can be based off it. The engine did fine in the smaller Liberty, which weighed 4200 pounds. The FSJ has more drag and when your frame is boxed, probably has the same or more weight than the Lib. When I increased the tires from 28 to 32 inch tires on steel wheels, the stock power was a bit lagging. I re-geared at the same time, but that didn't really make up all the difference. It was the added weight on the tires and wheels that took the punch out of it. I had to reprogram/tune the ECU to be satisfied with the power: boosting it from 160 HP to 190 HP and up to 360+ foot pounds. If you spend the money on the Cummin's crate 2.8, you will probably want to keep the warranty and not mess with some aftermarket tune. I think a 2.8 would work with a manual transmission for a MPG cruiser. Otherwise, too small and too under powered.

If you want a driver and RV tow rig, the 6bt could be a way to go. I would not put it in a machine you intend to offroad/wheel as it is too heavy up front and raises the center of gravity too much if you are not really careful. You are going to need stronger axles front and rear and may need to clearance / notch the firewall. Fitting a mechanical fan will require more length. I don't like how there is no room in every 6bt FSJ swap I have looked at. They look like the intake piping and motor were sandwiched in there and that you will have to take the inner and outer fenders and grill off to get to much of anything.
  • 65 FSJ Wagoneer, under the knife
  • 67 FSJ Wagoneer, peacefully taking a break
  • 94 XJ, long-armed on 33's. Bolt on ghetto fab fantastic
  • 16 BU, wife's snow commuter
Formerly: 06 KJ CRD (Constantly Repair Diesel)

User avatar

BaldBeardedBastard
Posts: 98
Joined: Fri Jan 29, 2016 2:52 pm

Re: Another Cummins swap

Post by BaldBeardedBastard » Fri Jan 14, 2022 6:46 pm

Hey Boomerules55,
I have a build thread going my Cummins 2.8 build. I am going to throw my $0.02 and say that its pretty much the ideal motor for the truck.

I definitely hear what Pablo is saying about the VM 2.8( his build thread on his 4bt is a definite read), but the Cummins 2.8 is a 170 hp, 310 ft-lb motor that weighs about 40 lbs less than the original 360 I had in it. Without a regear( still on the list) and 3.31s this scoots and I am getting around 24-26 mpg highway so far(skinny pedal and trans tuning hasn't made it too terrible representative though). It is not a monster by any measure, but it is a fun reliable motor that from the crate needed 3-4 wires hooked up.

I second what Pablo is saying- it depends on what you want to do with it. Dead simple and proven? 4BT is a great choice. More modern smaller displacement? 2.8 or maybe even an EcoDiesel(?). Want to pull a mountain and upgrade axles? 6bt. Sadness and slowness? Nissan SD3.3 :-)


Topic author
boomersrule55
Posts: 6
Joined: Fri Dec 24, 2021 10:17 pm

Re: Another Cummins swap

Post by boomersrule55 » Fri Jan 14, 2022 9:36 pm

Hey thanks guys for your in input, I have been actively looking at my options, and a 6bt is definitely out and a 4bt is my #1 choice like most guys, but the prices are thru the roof... I keep going back to the 2.8 and recently called cummins asking the usual questions about powering my GW, and also asked about other crate motors coming up in the future... they said there is talk about it, so if I can't something soon I will probably wait. After driving my 5.9 12V and 6.7 I am afraid I will be disappointed in the 2.8, but maybe not, I need to hitch a ride with someone who has a 2.8 in a GW and see for myself before investing 10K in a new motor. I won't be towing with the GW, just cruising around northern AZ, just want to get the waggy on the road!


Topic author
boomersrule55
Posts: 6
Joined: Fri Dec 24, 2021 10:17 pm

Re: Another Cummins swap

Post by boomersrule55 » Tue Jan 18, 2022 12:27 pm

Hey all, just picked up the new to me 4bt from a guy who had it rebuilt by Diesel Power Services out of Birmingham AL , this guy had it rebuilt last march to put in his jeep, but abandoned the project after getting to busy with work. He brought the motor out to NM to sell, thinking there would be more jeep guys out west, so after a 1100 mi 21hr solo road trip I got it back to AZ. I talked to to the shop manager at DPS and he told me it has a new head, pistons, rebuilt injectors, rotary pump and turbo, was completely gone thru and test run for a thermostat test, hopefully this will be a good start to the project. So on to next process of gathering all necessary components before pulling the old motor. I am looking at a 47RH-NP 241 combo out of of 12V dodge if I can find one, also anyone know of good motor mount kits for the GW, I would like to run hydraulic , and a direct mount power steering kit, thanks all.


Topic author
boomersrule55
Posts: 6
Joined: Fri Dec 24, 2021 10:17 pm

Re: Another Cummins swap

Post by boomersrule55 » Wed Jan 19, 2022 10:22 am

I am looking to install a direct mount vacuum- power steering pump combo to go on the 4bt with ve pump, does anyone know what years will interchange, I see them on Ebay and they look the same but the years vary, thanks.

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest