ENGINE SWAP -or- SELL! the final say for the most efficient square body motor!

dajn37

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I know this isnt adding much to the thread but my favorite pickup was my 2001 dodge 3/4ton extended cab with the 5.9 Cummins. It was my bosses pickup that was my work pickup. He has a fleet of dodge pickups. All diesel. The 01 had a utility box on it. 100 gallon off road fuel tank. When I was loaded, I was a little over 10,000 pounds. I could hop on I-94 and head to Fargo or Dickinson or wherever I was headed and get 20 mpg cruising 75mpg. I hope to buy one like it someday.
 

dajn37

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But it's always give and take with these things. A diesel is better for some things and worse at others. Not to mention diesel is quite a bit more expensive than gasoline. I was impressed with my 2000 suburban. On longer drives I could get 18mpg. Pretty damn good for a 5000 pound 4×4 and why everyone talks that 5.3 swap so much. But it sure is difficult to get something that hits as many points as you want. always give and take.
 

84 M1008

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First and for most I read the thread and I cant seem to find what rear-end gear you have. That's going to effect this a lot. Lets say you have a 3.08 or a 2.73 which is pretty much the only way your going to get near 20mpg with any of these motor options. Now on the other hand your going to give up a lot of towing power and as long as your ok with this just being your DD and just trying to get the best MPG you can then ok.

1.350- tried and true. reliable tons of aftermarket, but all it is, is a bigger version of the motor you have. So don't plan on getting better mileage with this option or 20mpg. Easiest way for you to make more power and easiest to swap by far.

2.5.3- IMO this is your best option, your going to get around the same mileage as the 350 but engine will be lighter, more reliable and welcome your square to the 21st century.Also check out the 4.8 that's a great little motor

3.6BT Cummins found in the dodge trucks- Your not going to get 20mpg. Bottom line. These engines are heavy but very reliable and make great power. Dodge guys will tell you all the time how great the mileage is towing 20k pounds. its all BS. A 1996 Dodge 12v cummins with 3.42 gears gets around 15 MPG and around 10 towing 10k. Problem is you will start looking at the simple cheap upgrades for it. Once you do them it will just spiral out of control and kiss any kind of fuel mileage goodbye(ask me how I know.)

4.4BT Cummins- great engine its just a 6BT with two cylinders taken off. You will indeed be able to achieve 20MPG or over with these motor and it wont even break a sweat doing it. Only problem I see with it, is its expensive(more expensive than 6BT) and parts are hard to find. With that being said not the best option

5. 6.2 diesel- Great motor but very under powered. I can say this because I DD one for a year. I had 4.56 gears and I could keep up with traffic till about 30MPH then I had to hammer it just to keep up. Didn't like it one bit, also doubt your get 20MPG more realistic is 16-18. Its possible 2wd truck, low(numerical) gears downhill you can achieve over 20 but everyday driving probably not.

6. 6.5 diesel- Made more power than the 6.2 but came with many problems along the way. Not worth the time and money IMO and got around the same mileage maybe a little less than the 6.2

All in all 20MPG is pretty hard to achieve in one of our old squares My personal opinion if I was looking to get the best mileage I can while still being able to retain reliability and made power I would without a doubt go with the 5.3/4.8. there all over the junkyard for dirt cheap.
I had an 86 M1031/K30 with the 6.2, banks turbo, and a super duty 700R4 that got 25+ on the highway and would walk away from any 6.5.
 

rpcraft

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Transmissions aren't irrelevant FWIW. That is why manufactures are switching to more gears and the automatics are becoming the only option. In many cases thanks to new lubricants and better materials finishing processes the power train loss is not as significant between the various types of gear boxes as well compared to what it once was. Obviously it has a lot to do with keeping then engine operating in it's zone of peak efficiency, and fewer gears makes it harder to accomplish that goal, so just food for thought. That being said though, if you are swapping for efficiency purposes, you would be better buying the whole package but that is kind of like stepping over a 10 dollar bill to pick up a penny.

To put it in better terms, do you like the current driveability and power level of your current truck? The add a FI system to it and it's just a simple way to add slightly better mpg's and far better cold start reliability. if you are a weekend warrior and drive your truck only when the sun is shining and the temps are right then leave it as is.

If you are truly wanting an easier path to reliable power and the guts are wrung out on your old bullet then an alternative upgrade path is an LS swap, but I would not consider it a cheaper option, and I'd also offer don't try adding your SBC peanut butter into the LS chocolate because it seldom turns into a Reese PBC. it usually ends up your LS motor is too much for the Basic 700r4 and your stuff gets Bruce Jennered, and then you got a motor that runs hot, blown out tranny, and still looking for a driveshaft.


Guys will tell you they did a 1K LS swap and did a turbo for less than 1500 and that their 700R4 works great. Everything has it's season. If you want it to be done right, look right, and more importantly, work well and last a longtime then you will spend much more than that.
 

Crispy

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...Bruce Jennered...hot, blown out tranny, and still looking for a driveshaft.

Great post, lots of good points...and that gem.

Just to play devils advocate here, soup to nuts ls swap (key being a good running donor) can be done under $1,000 plus the cost of the drivetrain. Really if you want the most basic setup (no headers, no AC, simple tuning, no performance parts) it can cost as little as 4-500 plus the drivetrain. If you're thrifty you can find a u pull it sale and score the drivetrain cheap, but the negates the good running donor part. At that point its a crapshoot.

I'm about $2,000 into mine which is on hold right now but I have just about everything except a tune and few small odds and ends but I paid $800 for my complete drivetrain.
 

Catbox

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I like this thread.

But for me I bought my truck to do chores and get driven just when I want too.
It has a rebuilt 454 in it with the SM465.
The only thing I would really want to change if anything is the transmission.

That would give the truck longer legs for when I need to go somewhere further than around town.
 

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