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Cummins swap questions & answers

42K views 68 replies 23 participants last post by  Chevelle468 
#1 ·
I am getting too many PM's to answer in a way that would help. In an attempt to help more, this thread is only for gas to CTD swap questions, thoughts, and concerns. I will post a list of major parts needed and the major struggles I encountered. My experience is only with a 2nd gen 1500, so my answers will be based on that.

Fire away.
 
#2 ·
Someone ought to sticky this. I've seen this question more than a few times on e this exact question. Good luck with it Jeff! :bigthumb:
 
#3 ·
Jeff, my cummings motor rattles to much and only gets like 15MPG basic driving,and with Diesel fuel running around the $3.00 mark around here,and gas only being $2.68 how hard or easy would it be to take out the cummings motor and put something more economical, like a 318 v-8 out of my 2wd 1/2ton 95 dodge I have sitting in the driveway??, I also would like to keep the turbo, will this swap work???
:flipoff: :flipoff: :flipoff: :D:
 
#4 ·
Jeff, although, I like to be the humorous one, I will be contacting you in the future, as A have my 98 up for sale,{think its already spoken for} but when I get the shop done, my new project is gonna be iether a 3rd gen {blown motor or taking good motor out{I HATE THE COMMON RAIL!} or a 99+ SD ford250,or 350, either way they are gonna be 4-door, but I am gonna go with the 12-valve engine again, and will be asking 100s of questions,wireing, fit, and junk thats not needed ETC ETC........so gear the fawk up!!!!! :bigthumb: peace- out! :flipoff:
 
#5 ·
THANKS!!!................JEEPBOY!! :bigthumb:

I think I will start acually with as far as knowing what kindof setup im gonna go with is 12-valve engine, P-pumped of coarse, but have really been racking my brain on going with a manual, or auto, I bought a parts truck a while back from up in N. MN and the owner had the simply for the engine, it was a 95 12-valve cummins 2wd with auto, he only used the engine, had an adapter machined to adapt the engine to the stock 2001 ford 250 auto, I guess Jeff what im trying to ask is, do you think if you could do it over again with the experiance you have gained, would you have tried to maybe go a diffeent route as far as say truck model?, ford? Chevy, I even would love to find a wrecked 3rd gen gasser {nice blown hemis are somewhat easy to find} :D: , and drop a 12-valve into it.... If you were to build another truck, and it was gonna be a DD, what would you have droped that motor into??? what setup? auto, manual?
 
#6 ·
I'll post up some questions for Jeff, since I was going to do a swap in the old truck.

What electronics/wiring is needed to do the swap? Assuming it's a 12 valve.

What kind of modifications did you have to do to the fuel system?

Was there anything you learned from the swap? Quicker ways, tips, tricks, etc.?
 
#7 ·
and for any one thinking about an old school swap ..... post up here too .... i am doing a first gen 12v diesel into a 79 trailduster (the same as any 70's power wagon)
 
#8 ·
On 2007-10-13 21:04, Deuce wrote:

Jeff, could you offer a short list of your biggest problems to at least get the ball rolling?

Thanks Deuce for moderating, although I got a good chuckle out of the edited posts.

Most of my main problems came from switching over to a manual. Once in, brakes were a big problem. I never seemed to truly have good braking after the swap.

Having a COMPLETE donor truck made things pretty simple. The motor mounts are in the same location, all the front end pieces such as core supports were totally interchangeable. The shear weight of the cummins was the biggest obstacle of getting it in.

Once in, wiring caused some headaches, especially behind the dash. I went without any WAIT TO START lights or associated diesel lights. I pulled the dash down (not out), but I just didn't find it worth it to re-wire the dash once I knew it would start. The speedometer/cluster plugged right into the 318 harness and worked like a charm. Running the wiring under the hood was a pain, but very do-able. I had to piece together two wiring harnesses to get all the lights to work properly. The front wiring harness is a diesel, the middle is the 1500, but for whatever reason -- I had to run the 2500 harness to get the all the rear lights to function. :dunno:

A 1500 suspension will hold a diesel up for a short time, but will eventually sag -- took mine about 30 days til a spring collapsed. All the steering components were interchangeable, including the power steering lines. One thing I ran into was making a auto steering column work with a manual. Easiest solution was to wedge the shifter into neutral permanently so the key would turn the ignition on and off without issues.

Again -- when swapping a manual at the same time -- lots of other things had to be changed. Foot pedals had to be added, bigger hole cut out in floor, and internal components like flywheel. I learned the hard way the internal splines of the t-case are different in an auto and manual.

Feel free to ask questions on any of the above. This is just a start to jog your brain.
 
#9 ·
On 2007-10-13 20:11, doodah wrote:
Jeff, although, I like to be the humorous one, I will be contacting you in the future, as A have my 98 up for sale,{think its already spoken for} but when I get the shop done, my new project is gonna be iether a 3rd gen {blown motor or taking good motor out{I HATE THE COMMON RAIL!} or a 99+ SD ford250,or 350, either way they are gonna be 4-door, but I am gonna go with the 12-valve engine again, and will be asking 100s of questions,wireing, fit, and junk thats not needed ETC ETC........so gear the fawk up!!!!! :bigthumb: peace- out! :flipoff:

If I had to choose a truck to drop a cummins in, I would have definitely went with a newer Dodge cab style or Ford SD. I am always looking for a newer cab from a big rear end collision, maybe even a side impact. Most people know that older 1 tons or such trucks need a kidney belt permanently attached to the seat. For ease of install tho, I would stick with the dodge base.
 
#10 ·
On 2007-10-14 18:25, doodah wrote:

If you were to build another truck, and it was gonna be a DD, what would you have droped that motor into??? what setup? auto, manual?

I looked into keeping the manual, but knew I would want to add lots of power. With the motor mods, I knew it would require a built auto tranny to handle it. After seeing the price needed for a good solid trans, the manual was simply the way for me to go. I wanted a truck to tow and wheel with at the time, so again -- the manual was it for me. I also thought a manual was cool.

Seeing where the truck has ended up now, I probably should have left the auto in it. I had to switch t-cases as well since the output splines of an auto trans was 23 splines, while the output shaft of a manual trans is 29 splines. Thus meaning if you swap from auto to manual, you will either need to get the right t-case or swap the shafts in the tranny.
 
#11 ·
On 2007-10-14 18:26, Jason wrote:
I'll post up some questions for Jeff, since I was going to do a swap in the old truck.

What electronics/wiring is needed to do the swap? Assuming it's a 12 valve.

ANSWER: To do nothing more than the motor, you will need the ECU and the wiring harness under the hood only. I am pretty sure you could get the diesel to start and operate with only this. A dual battery wiring setup is needed depending on the generation/year of the motor. Since its a 12V, you can run it with 0 power so long as you get it started. Having a complete donor truck will save you since all the wiring will be there. I am not running any diesel wiring behind my dash. If I were to do it again, I would never pull the dash, just the steering column if installing a manual. The speedo clusters are plug and play with the 2nd gen wiring harnesses.


What kind of modifications did you have to do to the fuel system?

ANSWER: I tried swapping tanks, but could not get the larger diesel tank in the truck. The cab configurations were different (went from a single cab long bed diesel to a n ext cab short bed gas) so the larger diesel fuel tank would simply not fit in the stock location. I cleaned the gas tank out as best as possible, then just screwed the top/diesel float into the gas tank. Added appropriate lines and vents -- good to go. I did nothing with the internal fuel system at the time. The only thing to run were correct fuel lines -- I went all stainless steel lines from the tank to the pump.


Was there anything you learned from the swap? Quicker ways, tips, tricks, etc.?

ANSWER: Research first. Know exactly where you want to go with the truck from the very start. Expect to spend more money than you budget, and more time as well. Get a complete parts list from a dodge dealer before beginning. I tried piecing it together as I went -- nickel and dimed TO DEATH. Buy OEM parts from the beginning, not POS autozone anything.
 
#12 ·
So im assuming if I get a 1st gen donor truck i sould be set to drop it into my 95 2500. Are the motor mounts the same? And what should I look for in a donor truck. What happens with the trany whats better my 46rh or the older 3speed auto? Also what with the tcase. What are my options. Thanx for the help
 
#13 ·
On 2007-11-08 07:33, nw4wheeler wrote:
So im assuming if I get a 1st gen donor truck i sould be set to drop it into my 95 2500. Are the motor mounts the same? And what should I look for in a donor truck. What happens with the trany whats better my 46rh or the older 3speed auto? Also what with the tcase. What are my options. Thanx for the help

Motor will drop right in. Motor mounts will be the same. Get as much of the wiring harness as you can. There will prob be several different connections that will need to be changed over -- having a complete harness will make it much easier. You may also need the wiring behind the dash -- fortunately I was able to use most of mine.

Tranny depends -- what do you plan on doing with it? I fully believe in the ever reliable NV4500. T-case will need to be changed or pulled from the donor truck. You need to decide which tranny you are going to go with it, and then get the correct t-case to match it. Spline counts will be different depending on which tranny you have/get.

I only know about the t-cases for 2nd gen trucks on up. You will either have a 23 spine for an auto, or 29 spline for a manual.

Hope this helps. Feel free to ask any more questions. Again, figure out where you want to go with the truck and what you want to do with it. Good luck.
 
#14 ·
From Kevin Carter via email...


My son purchased a 1998 Dodge Ram 1500 4wd from his grandfather and has been wanting to swap the engine out for a CTD. I have tried to read all your posts on paymentsucks and know you may be tired of answering questions about your swap or too busy, but if you don't mind I have a few questions.

In one of your posts you said something about writing up an article or paper on the swap and I would like to know where I can get a copy if you have done this.

Did I understand correctly that a 12 valve CTD would be a better choice for the swap because of the electrical changes needed for a 24 valve?

I would plan on swapping out the current automatic transmission with an automatic from a 2500 diesel and not try to convert to manual. Do you know if the 2500 transmission will mount the same as the old 1500 transmission? Do you think current linkage would also work?

From reading the post, I will also plan on swapping out the front axle but will the current rear axle work?

Will the transfer case need to be swapped?

Will the current drive shafts need to be replaced?

Will the radiator need to be swapped?

I'm a little confused on intercooler, do all CTD have an intercooler or were they added sometime later?

If the engine and transmission mount up without any modifications and the axles and springs swap out without any frame modifications, I don't see this being too big of a project to tackle. I certainly don't want to over simplify it, but I also don't want to make it more complicated than it really is.

Will the CTD and transmission from a generation 1 dodge fit correctly in a 1998 or should I only look at gen 2 donors? Not sure if I can find a complete donor truck but I have seen several CTD and transmissions for around 2-3 thousand and I would still need the front axle.

Any other advice you might want to throw on us, please do.

Thank you for your time,
Kevin Carter
 
#15 ·
Hey Kevin, gonna try to answer as much as possible here. I never did a write-up on it. I just simply ran out of time and motivation. This is why I started this thread -- it will be as close to a writeup as I will prob do.


The following answers reflect my experience only and are not necessarily a bible to follow. You should do lots of research and make sure you truly want to commit the time and money before starting. While its a straightforward swap and not terribly hard, prepare to be somewhat nickel and dimes to death along the way.



12V or 24V?

In my opinion, a 12V is the best way to go for simplicity. They are easy to work on, lots of parts laying around for them, lots of easy mods, very proven, no need to worry about the "53" block, and so on. It was the best option for me at the time. It is not necessarily going to be easier for electrical reason since you will still need to swap wiring harnesses (which was a huge PITA for me) -- again, it was just the simplicity of the 12V I was after.






Do you know if the 2500 transmission will mount the same as the old 1500 transmission? Do you think current linkage would also work?

Tranny mount is the same as well as the crossmember. I am not sure on the linkages, although I am sure they will prob work or need some light minor modification.







From reading the post, I will also plan on swapping out the front axle but will the current rear axle work?

Current rear axle will work, but may not work for long. I ram around on the 1/2 ton stuff for a few months until the front coils finally gave way. I would seriously suggest getting one ton axles, esp for the front. A rear Dana 60, 70, or 80 is cheap and an easy install.






Will the transfer case need to be swapped?

Yep -- you will need to find a 23 spline tcase to fit an auto trans. The poor 231 tcase out the gasser would not like the diesel power anyway.






Will the current drive shafts need to be replaced?

This will depend -- they don't need replaced, but you may need them lengthened or shortened depending on current lift and other mods. I used the rear 1/2 ton driveshaft and ujoints the whole time I ran one ton axles. I pulled the yoke off the 9.25 axle and installed it on the Dana 70 from the one ton. Splines on the yoke were the same. I would recommend a driveshaft out of a diesel since the ujoints are beefier, but I made do with what I had. I was budgeting somewhat when I did mine and did not want to have to get a new driveshaft made.

Front driveshaft should be fine tho -- look in a junkyard if yours doesnt work for one out of a diesel with your same cab/bed configuration.





Will the radiator need to be swapped? I'm a little confused on intercooler, do all CTD have an intercooler or were they added sometime later?

Yes - here is where having a complete donor truck was nice. While the radiator may work, I would want all the cooling power I could get to keep my investment running cool.

I would strongly recommend finding a cummins with an intercooler. I can't remember what year of first gens they were added in (maybe 89 or 91). Someone else can chime in.






Will the CTD and transmission from a generation 1 dodge fit correctly in a 1998 or should I only look at gen 2 donors?

I would find a second gen motor since more of the electrical is the same, esp behind the dash. The first gen motor will fit in just fine tho. I am unsure if the earily first gen trannies will bolt up to the 2nd gen crossmember tho. That would be an easy fix with minor modification if it didnt.

Finding a complete donor truck is the way to go, but I know its damn near impossible. I got lucky with mine -- but I also looked for a year and constantly made calls. The complete truck just saves you all kinds of time and money on parts, while giving you a chance to sell off the rest and recoup some money. It can be easily done without a donor truck handy, but this is where you research first and getting the needed parts before starting will come into play. Some of the longest delays came from waiting for the dealer to get my parts in -- and the constant run to parts stores got old REAL FAST.

GOOD LUCK.
 
#16 ·
Awesome write up.

I really wish I could find a 2500 gasser to do the swap, but finding one for whatever reason is getting rediculous.

Like I said in my post, I have a complete truck as the donor, so that will help.

Plus Im going to end up having a shop do the swap for me since I dont have the time right now, and Im in a time crunch to get it done before the end of December.

I dont care about the wait to start light, or the fuel in water light, etc.

My main concern was the wiring. But from what you've said, it seems to be not that difficult of a task.
 
#18 ·
On 2007-12-20 22:49, TxDuramaxRedneck wrote:
so pretty much you need to change all the drive train. I guess yall talked me outta swapping one in my 1/2 ton seems like it would be alot easier, cheaper in (long run) and more reliable to just buy a whole truck


Yep -- to reliably run the diesel, the whole drivetrain should be swapped. It is cheaper to just buy a whole truck, unless you find one heck of a deal like I did. Just keep looking -- it took me about a full year to finally find a deal.
 
#19 ·
Just curious, how come you never went into this into much detail in your buildup thread? :dunno:
 
#20 ·
On 2007-12-31 12:58, The Ultimate Maddog wrote:
Just curious, how come you never went into this into much detail in your buildup thread? :dunno:

When I started that thread, the cummins swap had been done for a few months. I really just didn't know where to start. There are so many little things that came up -- esp since I swapped in the manual at the same time. I had no decent pics either -- kind of hard to explain everything without the pictures.
 
#21 ·
What was your final cost when it was still on one tons? and how many hours do you think it took to get it to that point (the engine swap, the transmission, the tranfer case, axels, suspension, and wiring)

I'm thinking about doing this since you can't get a regular cab short bed diesel, and there's nothing wrong with my body or frame.
 
#22 ·
why are you having to fool with wiring inside the truck/underneath the dash? i can understand wanting the main gauges to work, but souldnt lights, and other misc accesories be dependent on something else besides the computer that controls the engine?
 
#23 ·
On 2007-12-31 13:17, superhawk2002 wrote:


When I started that thread, the cummins swap had been done for a few months. I really just didn't know where to start. There are so many little things that came up -- esp since I swapped in the manual at the same time. I had no decent pics either -- kind of hard to explain everything without the pictures.

Actually I guess a better way to have said that would be, How much did you pay for your donor truck, and did you have to buy anything besides the truck.

I was adding numbers up in my head, and it doens't make any sense for me to spend $1000 on 1-ton axels, then 1,500 to have them re-geared. Then $500 or so on 8 lug wheels, $250 on 1-ton steering. 1,500 on 5 inches of lift (when a 2500 suspension already puts me 2 inches higher, and 3" suspension lifts are like $700). I'm already up to like 4,500 and I'm still stuck with a 1500. If I can get a cummins, a nv4500, a heavy duty suspension, and t-case for a couple thousand more I'm there...
 
#25 ·
On 2008-02-20 00:07, Cereal Killer wrote:
What was your final cost when it was still on one tons? and how many hours do you think it took to get it to that point (the engine swap, the transmission, the tranfer case, axels, suspension, and wiring)

I'm thinking about doing this since you can't get a regular cab short bed diesel, and there's nothing wrong with my body or frame.


Final cost prior to rocks without suspension lift and wheels -- around 8 to 9,000 dollars. That includes both trucks and all the necessary things to swap. I had prob 100 hours in the actual swap of motor and axles. A lot of that was not knowing what I was doing and having to stop for small parts. Wasn't bad for a truck with 120,000 miles and tons of new drivetrain parts.



On 2008-02-20 00:25, Random Task wrote:
why are you having to fool with wiring inside the truck/underneath the dash? i can understand wanting the main gauges to work, but souldnt lights, and other misc accesories be dependent on something else besides the computer that controls the engine?


Different years and models had some various connections throughout the entire truck that were not interchangeable. My problems with wiring were a result of different year model trucks.





On 2008-02-20 13:57, Cereal Killer wrote:


Actually I guess a better way to have said that would be, How much did you pay for your donor truck, and did you have to buy anything besides the truck.

I was adding numbers up in my head, and it doens't make any sense for me to spend $1000 on 1-ton axels, then 1,500 to have them re-geared. Then $500 or so on 8 lug wheels, $250 on 1-ton steering. 1,500 on 5 inches of lift (when a 2500 suspension already puts me 2 inches higher, and 3" suspension lifts are like $700). I'm already up to like 4,500 and I'm still stuck with a 1500. If I can get a cummins, a nv4500, a heavy duty suspension, and t-case for a couple thousand more I'm there...

2000 bux for the donor truck. Had to buy lots of stuff. Read the above posts. For most -- it does not make sense to do the swap. I did it cause I had the time and found one helluva deal on a donor truck.




On 2008-02-20 14:28, halo 216 wrote:
well since I have a 2k 2500 its basically an engine swap with wiring? if i find same year engine with harness attached it should attach up to firewall?

Pretty much. Should be straighforward depending on your tranny selection. I can't be fore sure if the wiring will be the same -- are you getting a 12V or 24V? The dealership told me nothing would interchange except for the lights, but pretty much everything was interchangeable besides the dash wiring.
 
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