what to buy 5.9 or 6.7 cummins truck

J

jaybuller

USCG MK
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Mar 27, 2009
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Im looking at buying a newer truck. I want a 2005 to 2010 cummins 4x4 auto. not sure on what engine or tranny is the best for these trucks as ive only messed with 7.3s and 12vs. I just dont want to buy one with 150k and start having all kinds of problems with it. LIke blown headgaskets or injectors crapping out. Also do these trannys hold up good? Im only gonna be tuning it for now and setin it up for good mpg not gonna be going for big power any time soon. thanks yall.
 
go with a 03-04 they have the better piston design in them than the newer 5.9 motors but if you are stuck on 05 or newer go with either 05-06 they have less emissions crap on them to have to deal with.
 
ok so 03-04 for the 5.9, now how bout any problems with the 6.7s? i found a 2007 6.7 mega cab that i like with 133,000 miles on it. say it all runs and drives good no prblems and its only 23.500 for it.
 
also what is the expected mpg out of a stock 6.7l auto 4x4 mega cab on stock tires and stock lift.? and what can i do to get the mileage up over 20mpgs?
 
jaybuller said:
also what is the expected mpg out of a stock 6.7l auto 4x4 mega cab on stock tires and stock lift.? and what can i do to get the mileage up over 20mpgs?
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A few things would have to become decorations for you to get that kind of mileage. All the emissions stuff would have to go then put on a exhaust and a tuner. As soon as the egr goes you will need headstuds and probably a wastegate in order to keep things in check. The egr cooler really helps keep drive pressure in check with it off things can get out of hand quickly, there have been a lot 6.7's with blown head-gaskets. The 6.7 can get a little expensive in a hurry, 03-04 5.9 would be a lot cheaper. My truck got about 13.5 in stock form :doh: and had a check engine light every week it seemed like.
 
my 05(wrecked) and 04.5 both got 17-19 mpg with 35's with 50hp injectors and a good converter you could see 20 mpg in a 03-06.
my buddies 07.5 is only getting 14 mpg with all the emissions crap on it.
 
I would get a 6.7 and delete all the emission crap. The only downside is I have heard some stories of blown head gaskets. The nice thing about the 6.7 is a 6 speed auto and exhaust brake.

Tobin
 
I have heard the 6 speed auto isn't up to the task of a modified cummins motor and some guys are swapping out to a 48re
 
Backhoe man said:
A few things would have to become decorations for you to get that kind of mileage. All the emissions stuff would have to go then put on a exhaust and a tuner. As soon as the egr goes you will need headstuds and probably a wastegate in order to keep things in check. The egr cooler really helps keep drive pressure in check with it off things can get out of hand quickly, there have been a lot 6.7's with blown head-gaskets. The 6.7 can get a little expensive in a hurry, 03-04 5.9 would be a lot cheaper. My truck got about 13.5 in stock form :doh: and had a check engine light every week it seemed like.
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I had the same question as the OP and so the bolded statement: Is that only true if your racing it or does the EGR cooler keep drive pressure in check so much that without you pretty much NEED head studs?
 
semperfidoordie said:
I had the same question as the OP and so the bolded statement: Is that only true if your racing it or does the EGR cooler keep drive pressure in check so much that without you pretty much NEED head studs?
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I never blew my gasket but I did not run the stock turbo for long, it is a big part of the problem. As far as needing head-studs I would say yea cheap insurance compared to a down truck and having to pull the head off and all of that. If you just want a stock truck with no emissions and a stock charger I would put in studs, with just a tuner you can see about 475hp on the stock charger. At that level your gasket will give up in a very short time a waste-gate will help but your exhaust brake will probably not work as well as it should with a waste-gate in the system. The exhaust brake is going to create around 60 psi of back-pressure which should start to open the waste-gate some say it does not but if your gate is not opening with 60 psi under it then it is not doing its job.
 
Backhoe man said:
I never blew my gasket but I did not run the stock turbo for long, it is a big part of the problem. As far as needing head-studs I would say yea cheap insurance compared to a down truck and having to pull the head off and all of that. If you just want a stock truck with no emissions and a stock charger I would put in studs, with just a tuner you can see about 475hp on the stock charger. At that level your gasket will give up in a very short time a waste-gate will help but your exhaust brake will probably not work as well as it should with a waste-gate in the system. The exhaust brake is going to create around 60 psi of back-pressure which should start to open the waste-gate some say it does not but if your gate is not opening with 60 psi under it then it is not doing its job.
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Thanks for the help. I guess if I can find a decently priced 6.7 I'll be throwing studs, a tuner, exhaust and all the basics on it. Now if I want to delete all the emissions **** should I leave the EGR cooler in place and block it or get rid of it completely? I currently have all that **** deleted on my Duramax but this will be my first Cummins.
 
with a 6.7 over 20mpg is pretty easy with deletes i have 3 of them around the shop all over 20mpg and only one with head gasket problems was on mine but the other 2 are all stock on 60 horse tunes and deletes and easily get over 20mpg with no issues depends what you wanna do if you wanna make big power either get a g56 or plan on swapping to a 48re just my$.02
 
hmmmmmmmmm lets see, 3 grand to get all the deletes done and you have done nothing for performance, or take that three grand, do head studs, nozzles, kick ass turbo and a smarty for about the same and have about a 500 hp truck, that will need a 5 thou trans to handle it, or a beefy clutch.......
 
mikmaze said:
hmmmmmmmmm lets see, 3 grand to get all the deletes done and you have done nothing for performance, or take that three grand, do head studs, nozzles, kick ass turbo and a smarty for about the same and have about a 500 hp truck, that will need a 5 thou trans to handle it, or a beefy clutch.......
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$3K?? I deleted mine with a $900 H&S, a $15 flange I made and a $40 piece of 4" pipe....you don't HAVE to remove everything to delete it, just un plug it and get rid of the DPF;)

Chris
 
mikmaze said:
hmmmmmmmmm lets see, 3 grand to get all the deletes done and you have done nothing for performance, or take that three grand, do head studs, nozzles, kick ass turbo and a smarty for about the same and have about a 500 hp truck, that will need a 5 thou trans to handle it, or a beefy clutch.......
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LMAO, dude... $3k for deletes? why do people talk about **** that they have ZERO idea about? :confused:

MEANWHILE, all you need for a 500hp truck with a 5.9 is a Smarty and a turbo...

the "deletes" are a friggin' exhaust system... you're going to buy a programmer for a 5.9, so no big difference there.

but with a 6.7 you get the 03/04 piston design, more cubic inches, more reliable injectors, newer truck, etc. etc.

I'm driving an 03 because I got it cheap, but I've had my eye out for a good deal on a 6.7
 
thats the going rate for a complet job, not a hack job, by a local shop. just went through this last week with them about a truck a friend of mine was going to buy.
 
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I paid 380 for a turbo back 5" exhaust, 520 for a used smarty, and 100 for a complete egr delete kit.. Mine gets anywhere from 18-21.5 depending on how I drive it... I say get a 6.7!
 
6.7 injection system is a big plus over the 600 5.9 motor.

Tobin
 
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