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Cummins swap, what do ya think????

7K views 51 replies 18 participants last post by  xxxxxxxxxxOl'Blue 
#1 ·
Hi y'all, Well I really don't know if this is the right place to post this or not, but I've had a Cummins swap running through my head for a couple of years now. I won't be doing this right away. This is something that I would be collecting parts for and will do when my 7.3 gets really tired. I know our motors and the Cummins have advantages over each other as well as disadvantages. I used to drive trucks and the Cummins powered rigs seemed the best that I drove, so I figure the best motor should go into the best truck. Also the only real purpose for a Dodge is to provide these motors.

What I'm really after is to hear from owners of Fummins trucks about their experience with a swap and differences from the Navistar engine in the way it moves. I also am willing to hear any ideas on how to do this in the most cost effective way over time(I expect years of parts collecting), and good reasons not to do it besides fan boy loyalties.

Should I get a good block and build the engine a bit here and there, or save up for a complete engine and rebuild it?

Thanks
 
#2 ·
Unless you are building a dedicated sled puller, it is purely a novelty. I have no brand bias and actually have converted a Ford, my opinion is it's cool to have but really no major benefit.
 
#4 ·
I would think if your due for an eng. the cummins would get much better MPG.
 
#13 ·
That's what I'm really going for once the engine gets tired. At 107,500 I still have time to go for that to occur considering a well taken care of 7.3 lasts into the 300k range.
So I figure if I do this I should start collecting parts in the near future, or as my wife allows me project money. LOLLOL
 
#8 ·
*Subscribing!

I was thinking of this same thing when I wanted a little more towing power, but ended up doing injectors and new tuning (and buying an as-yet-uninstalled intercooler). I've toyed with the idea of trying to get my truck to run consistent 13's in the 1/4-mile so it can be a backup for my bracket car if it breaks, but traction is an issue with 2WD.
 
#15 ·
make that 3!! i averaged 20mpg bone stock. (3.55 gears)
if you not worried about money to convert id say go for it. but if you just want a lil more pep rebuild the 7.3 and some stage 1s custome tunes, and a intercooler. kinda my goal right now building a "tow" rig.
 
#17 ·
my 93 5speed cummins dually with 3.07 rear got 25mpg and 350hp..

92 4x4 5speed 3.54 stock gets 25mpg has no balls.

85 ramcharger with 3.73 35in tires and an auto got 13mpg

02 2500 4x4 auto. 18mpg all stock

92 2wd 5 speed pump tweaked exhaust and got 25mpg

89 auto stock 3.07 2wd got 30mpg no balls,

85 dodge gas truck 8mpg
 
#18 ·
97 OBS that was getting rock steady 17mpg every tank before 2 injectors went bad. Just installed new Swamps stage 1's, so anxious to see if mpg returns.
 
#19 ·
Check out my sig: the F350 (7.3) averages 14, the F250 (12V) averages 15.2 (14.5 winter, 16.5 summer). All basically city. I can do more to the 12V to increase mpg's (bump the timing) and recently changed injectors which will improve it too. Seems modified 7.3's lose mpg's based on my avg's compared to those posted on here.
 
#21 ·
Apparently I'm one of the few who has always gotten crap for mileage. I got 17 on the highway a couple time when new, but it's all been down hill from there. I'd be lucky to get 12 on the highway today.
 
#28 ·
I heard somewhere that you can keep the PCM but lose the IDM to control the E4OD?????? I wonder how that would work????????
It works kinda. I ran mine like that for a while, just have to hook the TPS up at a minimum then I had a switch to lock the converter. I am sure if you took the time to review a wiring diagram and see all the parameters the PCM uses to run the trans you could get it to run OK. Ultimately the PCS is the best way to go. Watch the forums, I got my PCS used for $600.
 
#27 ·
I know the milage debate is off topic for the cummins swap but those getting high MPG from their 7.3L 4x4 do you have manual hubs? Also, those getting low MPG do you have auto hubs? I'm about to do a SAS w/ manual hubs & wondering how much this will help my MPG. Thanks all. Sorry if I should have just started a new post or this ? already posted.
 
#39 ·
If you like the engine, I'd say go for it, it's your rig. I'd love to have a 72 Chevy CC LB 4x4 with a turbo charged John Deere 404 engine. Funding and time are the only things holding me back.

For now I'll stick with my stock truck and enjoy 21mpg.

J
 
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