D50 Diesel Build


Active member
I figure it may be time to begin a thread to document my slow burning ‘87 D50 diesel project.

I’ve a 1987 Ram 50(D50/MM) macrocab, 2.6 4G54, KM145 5 speed, 4x4, that is rust free, has good bones but a tired engine w/200k+ miles. After looking rather extensively for this exact combination, I lucked out and ended up finding it a block away in my neighbor's sideyard; they’d owned it for years and years and only kept it around for the odd dump run/lumber haul/etc.

The general plan is to swap in a new D4BF (4D56t) along with a beefed up drivetrain, suspension, brakes, etc from various Gen 2s and MSs. My ultimate objective is to build a robust, simple, fairly easy to maintain/repair, minimal electronics, long lasting, and reliable truck capable of hauling decent loads, solid fuel economy, and long distance trips/possible overlanding expeditions.

I don’t do any hard core ‘crawling’, but rather lots of hauling firewood/motorcycles/soil/etc, winter driving in heavy snow/mountainous terrain, lots of tough dirt/gravel/logging roads, and long road trips. The private hope is that I may be able to take off on a long self supported overland trip in the coming years, perhaps head for Tierrra del Fuego; toughness, reliability, range, and simplicity are paramount.

I’ve spent the past year or so tracking down and sourcing odd, specific, and hard to find parts, and after a less than focused spring/summer, am nearly at the point of tearing the D50 down to the frame and building it back up. Below is a broad stroke synopsis of my planned build, parts not yet acquired are in grey italics:

-Brand new crate D4BF (4D56t) motor,
-EGR block off
-EGT sensor
-Boost gauge
-2.5” exhaust
-Front mount intercooler
-OEM 2.6 SWB 3 row radiator

-OEM viscous clutch fan
-Block heater freeze plug
-Snorkel intake
-Water separator fuel filter/heater
-Fumoto oil drain valve
-Tune injection pump

-V5MT1 5MT, rebuilt - ‘97 MS 3.0 ‘LS’, JA4MT31P2VP004615
-4D56t to V5MT1 bellhousing - ‘06 L200 K74

-Centerforce II Clutch, # CFT581780
-MS rebuilt MC/SC
-CAD free 8” 4.636 front diff - ‘03 MS 3.0, JA4MT21H03J006737
-100mm CV shafts - ‘94 SR 3.5, JA4MR51M3RJ001621
-9.5” 4.636 locker rear leaf spring axle - ‘99 MS 3.5 ‘LTD’, JA4MT41R1XP033372

-Marks 4WD 3.15:1 transfer case gears, # PAJ-GEN2-3.15M
-ARB front & rear lockers, # RD110 & RD212
-ARB compressor, # CKMTA12

-MS 315mm front caliper brackets - ‘01 MS 3.5, JA4MT41R71P030970
-MS rear disc brakes - ‘99 MS 3.5 ‘LTD’, JA4MT41R1XP033372
-MC/Booster/Proportioning valve - ‘97 MS 3.0 ‘LS’, JA4MT31P2VP004615

-Stainless braided hoses
-Fresh rotors, pads, rebuilt calipers/MC

-MS UPCA & LCA - ‘97 MS 3.0 ‘LS’, JA4MT31P2VP004615

-OEM upper & lower ball joints
-Sway Away HD torsion bars - # 1726
-OME HD leafs & shackles, # CS023R & OMEGS16
-Poly bushings throughout
-Bilstein 4600 shocks

-MS sway bars - ‘99 MS 3.5 ‘LTD’, JA4MT41R1XP033372

-MS rebuilt steering pump & box - ‘97 MS 3.0 ‘LS’, JA4MT31P2VP004615
-MS knuckles - ‘97 MS 3.0 ‘LS’, JA4MT31P2VP004615
-MS idler w/ADD chromoly kingpin kit - ‘97 MS 3.0 ‘LS’, JA4MT31P2VP004615

-OEM tie rod ends

-LED bulbs throughout
-JW Speaker LED 5” x 7” headlights w/heater - # 8910
-Dakota Digital tach converter
-Pyro & boost gauges

-D50/MM ‘sport’ dash gauges w/tach & speedo
-New stereo
-Dual batteries
-Glow plug timer switch
-Cruise control
-Air conditioning
-Intermittent wiper switch

-Aisin FHM-002 manual locking hubs

-16” x 7” steel ‘NATO’ style rims, 5x
-Falken Wildpeak ATW3 235/85r16, 5x

-New OEM paint, B76 Twilight Blue Metallic
-POR15 frame/etc
-Flat bed w/drawer, under deck boxes, & 2” reciever
-Tubular front bumper w/Warn winch
-Skid plates
-Larger or 2nd fuel tank

-POR15 floor
-Insulation & soundproofing
-New grey carpet

-OEM grey macrocab interior plastics/trim
-OEM grey center console

-Custom ABS door panels
-Bucket seats w/arm rests, possible bouncy seat bases if they can be made to fit
-Tint/security film

At the moment I’m monitoring MrRay’s thread regarding the variances in V5MT1 input shafts to determine if I’ll encounter the same issue and/or how to rectify it, https://expeditionportal.com/forum/threads/seeking-help-with-dead-jdm-v5mt1-mystery.208734/.

I bought a complete ‘97 MS w/V5MT1 to harvest parts from and haven’t yet pulled the V5MT1 to determine if it’s input shaft will fit the 4D56t to V5MT1 bellhousing I imported from Europe many months ago. I was entirely oblivious to this potential complication until MrRay posted a few days ago; the discrepancy in input shaft diameter hasn’t been mentioned anywhere that I’ve been able to find.

Once I’ve the V5MT1 pulled, I’ll open it up, address the input shaft and anything else suspect and then hopefully be able to verify which set of transfer case gears I need to order from Marks 4WD in Australia. I’m strongly leaning toward the 3.15:1 gears if I can get them as I see no downside beyond slower speeds vs the 2.7:1 or 2.85:1 but much more control and torque at low speeds, yet will need to wait until the transfer case is open to verify spline count and shaft diameter. https://www.marks4wd.com/low-range-overdrive-gears/paj-gen2-3-15m.html

Anyone have any advice regarding my choice of the 3.15:1 gears?

The other aspect of the build I’m trying to figure out is what radiator/fan configuration to go with. I’m well aware of the fact that the D4BF/4D56t needs a robust cooling system to protect the alloy head, esp when driving slowly w/AC, etc.

Option 1 - Take advantage of the fact that I’ve a brand new clutch fan, and pair it with a Gen 1 2.6 SWB 3 row brass radiator after having it rodded out. I’m fortunate to have a great local radiator shop about a mile away, 2.6 3 row radiators are pretty easy to find, relatively cheap, and benefit from the ability to be brazed via torch should any repairs become necessary in the middle of nowhere, and the fan can be easily modified to run constantly should it be necessary.

This seems to be regarded as a more than ample and reliable set up by many on the Australian Pajero forums with much more experience with the D4BF/4D56t motor, blisteringly hot conditions, and lots of off road/overlanding culture.

Option 2 - Members of the mightyram50.net forum, who are more into the mini truck and performance ‘scene’, have figured out that Nissan 240 SX radiators are a near perfect size match for the D50/MM. Mishimoto offers pretty nice aluminum 240 SX radiators in both 2 and 3 row as well as dual electric fan shroud. There are plenty of cheaper no name options on eBay/etc, but Misihmoto seems to have a pretty good reputation and a lifetime warranty.

-2 Row, https://www.mishimoto.com/nissan-24...MI96KmqLPF5AIVAcJkCh1o_QePEAQYASABEgLjmvD_BwE
-3 Row, https://www.mishimoto.com/nissan-240sx-s13-performance-aluminum-radiator-89-94-sr20-triple.html
-Dual electric fan shroud, https://www.mishimoto.com/mishimoto-nissan-240sx-aluminum-fan-shroud-89.html

The 3 row aluminum radiator would be nice insurance against potential overheating when heavily loaded, in the heat, running AC, and on rough terrain. My best friend is an aluminum boat welder by trade so I’m confident I’ll be able to modify/add any brackets needed to securely mount it.

My hesitation lies with the potential reliability, or lack thereof, in remote areas. Aluminum is more prone to damage and much more difficult to repair in less than ideal circumstances. Additionally, I’ve no doubt the electric fans draw more than enough air, w/potentially less parasitic drag, but should they fail, they can’t be easily repaired on the trail whereas the clutch fan can be physically wired/zip tied to run constantly, ensuring you can limp home.

I’ve saved up and paid a pretty penny for my brand new motor and want to adequately protect that investment, so the few hundred dollar price differential between the two setups isn’t much of a concern. I’m confident the aluminum radiators and electric fans are amply reliable, they’re spec’d on nearly every new car, and maximizing my MPG is important to me, yet despite that I’m hesitant about going in that direction. Cooling is one aspect of a truck that can really ******** you if it fails in a rough spot, and my luck typically follows Murphy’s Law.

I’d welcome any good advice or input.
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Looking for that thing i just had in my hand...
Thanks for starting the thread over.

On the aluminum rad, make floating mounts (like what modern cars have) because the aluminum core does not like to flex at all. Our old copper/brass cores don't give a ********, that's why they can be hard mounted. It'll last a long time if it's not hard mounted and you use proper coolant (heavy use service intervals)


Active member
Thanks Toasty.

Think the increased cooling of the aluminum radiator, properly mounted, would out weigh the loss of durability or would an OEM 3 row radiator in top shape, fully rodded out/etc, be sufficient?

BTW, outstanding work on the SAS swap, I've been following along on IG and you're doing really great and clean work, its a joy to watch.


Looking for that thing i just had in my hand...
The OEM radiators are fantastic, i run a stock radiator and cooling system in my Montero. The only mod is a thermal switch in the AC fan, i can wheel at altitude or crawl in the desert while running a AC with no issues.

Thanks! Glad you're enjoying my project.


camp loser
😁I'd also recommend getting a water injection setup post your inner cooler setup Ideally you'd go 1 per port but thats not a have to, you'll find going thru the mountains you'll have tons of power left over but due to egt's you'll have to slow down so having the water injection helps cool that flame and keep you moving down the hiway at speed. You may need to weigh this out for your self first i was running 37" mil surplus tires and the heavy wheels with inserts to match so that makes a difference, this was on a 89 2dr montero with a 3.0 yota turbo diesel, not inner cooled. with 31's on it i ran 80 mph up the same hills and never came out of overdrive. diesel is awsome i love that motor.


Active member
Lord, I'm anxious to see how much power this project will end up, how usable it is, EGTs, MPGs, etc. There seem to be so many variables at play when reading of other's experiences and impressions:

New crate vs tired/used/high mileage/unknown history motor
Intercooled vs non-intercooled
Gearing, 4.22 vs 4.636 vs 4.9
4D55t vs 4D56t/D4BF
Tire diameters, widths, & weights
Heavier LWB vs lighter D50/MM/L200
Auto vs 5mt
Stock vs larger(2.5") straight exhaust
Injection pump tuning/settings

The biggest take away so far is that virtually everyone who has experience with or undertaken and documented a swap with this motor seems to universally love it, so I've really high hopes; you, 4D55Performance, Jeff@QuadShop, PLH, Toasty, etc.

Once I've the truck up and running and the motor broken in a bit I'd like to explore more in depth tuning options like injection pump settings, water and methanol injection cooling, boost levels, and hopefully get it on a dyno.

Thanks for the advice and input, please keep it coming, particularly those of you with direct experience with this motor and the mods I've planned.
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I can contribute.
cooling, the newer brass cores from pacific, and others, offer louverred fins, and dimpled tubes.all in a successful effort to increase cooling efficiency, without increasing size.
I am going to address the cooling system this winter on my 6G gen 1 montee.
I will flip the axle support arms, tie them into the LCA lower bolt, and this leaves a perfect space to install a 3.5 gen 2 radiator, with the above mentioned 3 row core.
my goal is to almost never have to use my Taurus elec. fan.
clutch fan for me is best option, but heading the list of my many faults is apparently I'm a lazy goon, so I tossed all the fan aparatus, in favor of a 25 minute timing belt change every year.

I've owned and own diesel and gas. I'm curious about the Hyundai engine.
I'm leaning toward a 4g64, due to the huge support for that engine. the incredible cheap power they generate, and quiet operation, coupled to light weight.

the diesel, meh. my experience in a small light rig is they don't have the h.p. I like on extended long, drives, think, west texas.
so. I hoped to be proved wrong, and buy a crate 4Dbf myself.
and noise I'm so dang tired of noise.
diesels are dam noisy.


Active member
Thanks for the input 'Round.

I'm leaning toward running the OEM viscous fan mated to a rodded out OEM 3 row radiator from a 2.6 SWB gen 1. Perhaps I'll end up with an aluminum radiator/electric fan set up once I've the truck up and running, depending upon the temps and mpg I see.

I'm pretty confident the crate D4BF with an intercooler, V5MT1 5mt, 4.636 gearing, 3.15:1 t case gears, and 235/85r16 AT tires will fit my needs as far as power and torque goes. Spencer (4D55Performance) has a fair bit of experience with this motor, as well as the earlier 4D55, and has posted the following based upon his impressions:

"To answer a few questions these engines make a lot more power than advertised. The figures always listed are the 4D56 out put figures from 1992. This motor has changed a lot over the past 23 years. I would say they make more like 125 hp and 200 ft lbs of torque. I have one in my 1983 MMM and it achieves around 28mpg. It feels like it has as much power as my 2014 Cummins. The thing just flat out moves and it does not care if you are going up steep mountain grades in overdrive. They are no where near as fuel efficient as the 4d55 but the trade off is worth it for the power. The power band is also very different than the 4d55. The 4d55 makes peak torque at 2900 RPM's while the Kia 4d56 makes peak torque around 2400 RPMs. The Kia 4d56, as I call it, is a much much more reliable engine than the 4d55. All the issue have been resolve so these new engines are good for 500K miles where the 4d55 was only good for 100K miles. They are just worlds apart."

Since I'll be tearing my truck to the bare frame and fully removing and stripping the cab for paint, I'll be making extra effort to add as much sound deadening and insulation as possible to both sides of the firewall, floors, doors, ceiling, etc, as well as new carpet to reduce noise and aid in cooling and heating.
ok good news on the diesel. on my rig i can go either way 'cause i have a wrecked diesel from japan, but here is my next question:

the importation from Korea, was it smooth and trouble free?
Kia 4D56
they are the same engine??


Active member
Yeah, the Hyundai D4BF is the same motor as the Mitsubishi 4D56t. There are a few very minor differences like valve covers, front vs rear sump oil pan, etc but otherwise they're exactly the same. My understanding is Hyundai bought the design/rights from Mitsubishi several years ago and manufactures them.

I ended up buying my motor from another vendor I got in touch with via either EC21 or Alibaba, I forget now, but it took quite a while to convince him to sell me just 1 motor, his minimum order quantity was much higher, something like 25+, so I'm not sure I'd recommend him. The link below should work and is a direct vendor for Hyundai Mobis, which is the parts and service wing of Hyundai.

Importing it was a bit nerve wracking at the time not knowing what exactly to expect per EPA import requirements, etc, but ended up being no problem at all.

The biggest hitch was figuring out a payment option both the vendor and myself were comfortable with. With such a large purchase and having no experience with him or reputation/reviews/etc to count on, I wasn't comfortable with a simple wire transfer; should something go wrong I would've had no recourse.

The vendor didn't accept credit cards, and repeatedly declined several of the escrow services I suggested, despite my offers to cover the fees. He ended up relenting and accepting Paypal, but after the transaction made a big deal out of the cost of the fees it cost him; evidently he was unaware of how much it would actually cost. As a result, I highly doubt he'd agree to another Paypal sale.

The vendor I bought from put me in touch with a broker who took care of everything and I want to say the shipping/broker fees were +/- $1,000 USD, on top of the +/- $3,000 USD for the motor.

For me, the most stressful element ended up being the waiting for my motor to clear customs with the federal gov shut down looming. I ended up picking it up about 36 hours before the shutdown went into effect on 12/22/18, and had it not been cleared by then, it looked like I might have been on the hook for a massive 'storage fee' from the bonded warehouse it was stored in. Admittedly though, that was merely a bizarre coincidence and shouldn't impact you or anyone else's purchase

My advice would be to get everything in writing in advance and pay via some method that offers you a degree of protection/insurance, escrow service, Paypal, credit card, etc, but should I ever want or need another motor, I'd have no hesitation ordering again, the value is just too damn high compared to anything else on the market.
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wow, great news. I believe I read about ur tribulations elsewhere on the net. or someone similar.
3000 is boomin' dirt cheap for a new motor.
brokers offer an escrow of sorts, a payment transfer f.o.b., after its free on board, or did for commodities.
perhaps a single engine is too much trouble.
I'm a little surprised the shipping was so costly though.
did it come into l.a.?
now I'm chasing a diesel concept again from what u say, I can do this quite nearly as cheaply as building a gasser.


Active member
The +/- $1,000 covered shipping, import fees, duty, broker fees, bonds, etc from Busan, South Korea to Seattle, WA where I picked it up from a bonded warehouse not far from the port.

The other option is to contact Maximum Overdrive just outside Vancouver, BC, several others have sourced D4BF engines from them, http://www.maxoverdrive.ca

I'm fairly certain that's where Jeff@QuadShop acquired his for the diesel Mazda B2600i he's building, https://www.expeditionportal.com/forum/threads/my-mazda-diesel-expedition-project.29762/
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I wondered if Canada was the place to buy.
jam it in the back of the pickup, and head home. BC, is just up coast from me.
u say the power of the 4D, is dramatically improved over the first series....thst would be fantastic

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