6.7 or 5.9?

[dutch6]

Dodge has become our truck of choice since we made the decision to tow a 14k trailer. Question is, which setup? I like the idea of the auto 6 speed and the exhaust brake but am concerned about engine problems with the 6. 7 Ideally, cost wise I would like to buy a 2006 5. 9, quad cab dually 4x4 long bed to tow with. Should I be concerned with the reliability of the 4 speed auto available that year?

Can I put an exhaust brake on a 5. 9, 4 speed auto without affecting any warrantys(Dodge or extended)?

Rear axle ratio: 3. 73 or 4. 10?

I would like to "do it right the first time" and get the correct setup. Any advice/recommendations would be appreciated.

 

[jgillott]

First of all, welcome to TDR. I believe you will find a wealth of information reguarding the truck you decide on.



You are correct in your understanding of the history that the 4-speed autos have had over the years. Some have had many reliability issues with them, especially in high performanc/heavy towing applications. However, the newer autos seemed to have gotten somewhat more reliable as the years went on. There are many aftermarket companies out there that build great transmissions for these trucks if you ever do have a failure.



Though they have only been on the road now a little over one year now, many have reported great performance out of the new 6 speed auto. I don't own one personally, but I have driven several. The integration with the factory exhaust brake is great and their overall drivability is much improved over the previous generation 4-speeds, at least in my opinion.

 

[Simplysmn]

I would say go drive the truck that you like and judge it for yourself Yes the 6 sp auto is sweet along with exhaust brake but your the one that is puttin out the money in my oppinion I would go for the 6. 7 and auto but that is due to the fact of I own one and love it yeah fuel ussage Stink's but it has the power right there when ever you need it .

 

[Coalsmoke]

Just a note on fuel economy, for some of us at least its not all that bad. I am at 18. 7MPG mountainous driving with only 4,000kms on the truck, so its not even close to being broke in yet. Every tank has been getting better than the last one in terms of MPG. it will be interesting to see how good it gets once things are broken in.

 

[TAbbott]

Having been down the "emissions road" with big trucks and being familiar with what happens to durability, economy, maintainance, longevity, etc. when you start adding EGR, mucking with the injection timing, adding particulate traps, adding more EGR, more complicated electronics, and more expensive and complicated mechanicals I opted to buy a 5. 9 before the 6. 7's became the only thing available. I haven't been sorry.



While the 6 speed auto may be nice, I still remember how to shift a manual transmission and I wouldn't trade my 5. 9 for a 6. 7. Yes, in stock form, the 6. 7 may make a bit more power, but the aftermarket more than makes up for that if more power is what you want.



Just the fact that the 6. 7 cylinders are siamesed would be enough to scare me. That's how chevy got a 400 out of a 350 small block, but when you really started working them the 400's would give up because of inadequate (no) cooling between the cylinders. The 350's were still being made long after the 400's were history.



JMHO, but I'm unconvinced the 6. 7's are an improvement. Plus, the smaller engine should deliver better fuel mileage, all else being equal ... and it's not equal! The 6. 7 has all of those other things mentioned above going against it.



It's only plus, as I see it, is it's comparatively cleaner exhaust,. Since I live and drive mostly in the desert where we have lots of wide open spaces and relatively few people, I'm not overly concerned about my particular carbon footprint. JMHO.

 

[Simplysmn]

Well Tabbott you have some good point's but I will tell you this put a stock 5. 9 next to a stock 6. 7 with same weight and there will be no race the 6. 7 will walk all over the 5. 9 hands down auto to auto pulling and stopping is just unreal with the 6. 7and auto combo and this is from hands on experience not just hear say .

 

[TAbbott]

Well Simplysmn, it should. It's slightly over 10% larger in displacement, rated at 6. 5%+ more torque, and nearly 7. 7% more horsepower. It also has the benefit of 2 more gears in the auto transmission than does the older model and it's peak torque occurs what, 200 rpms lower. It also has an exhaust brake (or equivalent more complicated turbo that acts as an exhaust brake) standard, while mine was an option (aftermarket PRXB). On paper at least, it's no contest.



With all that said, and I've not driven one, I'd be willing to bet that once I got my old 5. 9 handshaker into 4th gear, any contest would be over and it wouldn't be the 6. 7 coming out on top. JMHO. As they say, that's what makes horse races -- differences of opinion.

 

[Coalsmoke]

There really is a noticeable difference with these 6. 7s, not just in paper #s but in how they perform. TAbbott, you should go take one for a test drive, you might like it so much you'll buy it The first thing I noticed was the unreal power band, and it gets better from there, but no point putting it all on paper, a person has to drive one a bit to see for them self, as every person should. No-one should be taking these 2cent opinions as gospel when making a big truck decision. Also, why are you worried about siamese cylinders. I have found a couple of people bring this point up in the past, but never properly validated, and really unless we are planning on trying to bore the block or even jam 800hp out of it, people shouldn't need to worry about it. In fact, one could argue that a siamese block can generally handle more abuse due to its generally increased rigidity, but that's a whole different ball of wax. If these engines start loosing heads at 100,000miles in mass numbers I'll get worried, until then, I have faith in Cummins and the fact that siamese bores are nothing new to the engine market.

 

[AMink]

You can get a Jake brake on a 2006 5. 9. I have one on mine and love it. It works great. I can't compare the engines; never drove a 6. 7. The 48re transmission on the 06 is WAY better then the 47re that was in my 97. I think the newer 4 speeds are as good as any stock transmission out there, including the much vaunted Allison. No, I can't prove it, but it works very well. Mileage isn't where my 12 valve was, but then again, neither is the power!:-laf I will trade a few mpg's for a whole lot of hp and torque any day and the CR 5. 9 has that in spades. On the other hand, the 6. 7 is good too!

 

[jtwcummins]

Don't drive a 6. 7. I went to look and took one for a test drive. Sold my 97 12v and bought new truck. Pushing 10k miles and love driving it. As I say over and over, the hardest part about driving the 08 is keeping my foot out of it and that really kills mpg. I found my overhead within a couple of tenths of hand calculated mileage and if I pay attention to what my right foot does get 17-18mpg driving around here, about the same as my 97.



Hiway speed is hard to control since 2000rpm is close to 80mph. 2 OD gears are nice.

 

[EArp]

I'm certain the 6. 7 is a great truck. I guess the determining factor would be if the ability to upgrade the engine/transmission with power adders and such is an issue. If you want to upgrade, go with the 5. 9 no doubt. There's so much more aftermarket stuff you can get your hands on. Obviously once you start upgrading the 5. 9, there would really be no comparison in power and towing ability. As a matter of fact, for only a relatively small investment, i'd be willing to bet with an installed exhaust brake and a smarty jr. , you'd out-tow any 6. 7. In addition, the 5. 9 stock will get a bit better mileage and it's a tried and true motor that you KNOW will last as long as you maintain it properly. JMHO.
Thanks
Eric

 

[Coalsmoke]

5. 9s have their fair share of issues too. Last thing I'd want to buy is a 5. 9 engine that has been juiced up and run a bit too hot and now might drop a valve seat or a oil nozzle (just a couple examples if we are going to sit around and talk about what-ifs). Anyways, it is my opinion, that the 5. 9 just can't match the 6. 7 in terms of its mapped power band and refinement. Sure the 5. 9 can be made to have 400HP fairly easily, but with the power band on the 6. 7, the 350HP is all I need and then some. That said, if my 08 came with a 5. 9 in it would I love it any less? Probably not. Like everything, different strokes...

 

[dutch6]

Interesting that you mentioned the 4 sp transmission as that was part of my question too. I would like to buy a '06 3500 quad cab LB, DRW to tow my 14k trailer with but I am concerned with the 4 sp trans reliability and the compatibility with the exhaust brake. If a few more of you folks would weigh in and comment on the 4 sp trans I would appreciate it. Besides, $30k for an '06 is way better than $45k for the '08.

 

[RWPor]

5.9 vs 6.7

I have an 07 5. 9 with a 4 speed automatic with 17k miles. The freeway milage is 23 mpg this has been repeated several times. The milage in the 5. 9 is better than the 6. 7's 15 /18 freeway. The 48 re is fine and has been made much better over the years and an afetr market TC and VB make it a very reliable. Usually the problems with the transmission are from chipping the engine and adding more hp and tq. I have had no problems with the truck.



When I bought mine , new , I had a choice between the 5. 9 and 6. 7. The 6. 7 was having many problems with codes and poor milage and many reflashes.

Since mine is also a daily driver I don't have to worry about blowing out the dpf and plugging everything up driving around town. I have a a3. 5 trailer and it does just fine.

 

[Simplysmn]

Tabbott well said and I am sorry if I came off wrong but theses new truck's are just Plain Awesome yes I had my first gen motor in a 85 crewcab and Loved every min of it and did alot of pulling with it but I guess it all comes down to what the person buying the truck wants . and the seat of the pant's and expression on your face when you drive a 6. 7 tell's it all .

 

[dutch6]

Since I will probably be buying used, the issues of a used truck having been "juiced up", overworked transmission or other items of abuse could be a problem. Would the onboard computer store codes to that effect? Are there any other ways to check a prospective truck than just relying on a Dodge technicians word?

 

[Coalsmoke]

The easiest thing to do is to buy new, the second easiest thing is to find a truck from a single owner whom you feel takes exceptional care of their equipment and understands the cause and effect relationship of maintenance, etc. Someone like myself who can provide reasoning behind all maintenance intervals, can provide numerous sequential oil analysis reports and good thorough records of all work I've performed on the truck. That's not to say that these things are necessities, but when I am helping a new CTD owner look at trucks, these are some of the first items I want to know about before starting the inspection. Maybe look for a long time TDR member selling their truck. Otherwise, you can take an oil sample from the trans and engine and send it off for analysis. That will give a bit of an idea, but without having an oil analysis pattern to go off of from that specific truck, its usefulness is limited, and if they just changed the fluids it wont tell much other than the oil is good to go some more.

 

[LILHauler]

Since I will probably be buying used, the issues of a used truck having been "juiced up", overworked transmission or other items of abuse could be a problem. Would the onboard computer store codes to that effect? Are there any other ways to check a prospective truck than just relying on a Dodge technicians word?

I have to agree with you dutch. I wanted to buy used also and all the trucks I checked had the potential of bing at the rigs with lots tons of hours from idling. Not the best thing when the odometer only shows 60K miles. I had to get the hour meters checked all the time by a tech. Lots where juiced at one time, you can tell by the left over Velcro and they handled very used also. We went to an out of town dealer that had 5 used trucks that fit our wants 5. 9's and 6. 7's with less that 30K on them. After driving many 5. 9's we drove our first used 2007. 5 6. 7 auto. 2 blocks was all I needed to tell my wife and I that this was the truck hands down. Tight steering, smooth shifting and tons of power and this truck had less than 25K on it. The mileage is right in between some of the 5. 9's I drove. One 5. 9 auto with 4. 10's would only get 11mpg. This 6. 7 is getting me 17mpg. So is this mileage that bad, no I am happy with it and it's power it puts out. Not a single problem with it after adding 5k miles.

I tell my wife to drive it with an egg under your right foot. It will light up 4 (DRW) tires around a corner in a blink of an eye. Does she love to drive it?? If she had the keys to it, she would drive it all the time

 

[EArp]

When I bought mine, I had the choice between the 5. 9 and the 6. 7. I opted for the 5. 9 for really only a couple reasons. I don't like all the emissions stuff on the 6. 7, and I didn't like buying a motor that's still so new to come out. In the future, I know if I buy another new truck it'll have the emissions stuff on it. When that time comes, i'm sure i'll feel more comfortable knowing the 6. 7 has been out for a while. Right now, i'm extremely content with my decision. I'm getting an average of about 20 mpg, and i have the comfort of knowing when my warranty runs out i've got alot of options to upgrade to a super powerful truck if i want to. That said, if the 6. 7 didn't have the emissions stuff and had a proven track record, i would've probably chosen the 6. 7 for the upgraded transmission and installed exhaust brake.