5.9 or 6.7 and which gerabox for towing?

[birchit]

Hi together,

I am thinking about switching to a cummins instead of mine 6.4l PW 2016. I tow around 7800 lbs 20 times a year and 4500lbs around every second weekend. We have steep mountains with around 14-18 percent slope.

What combination of cummins engine and gearbox would be the best choice? Searching for reliability with standard engine setup (maybe with EGR and all the **** off).

I had with the 66rfe after 111k following issues: Last gear broke down, so we rebuild the gearbox with SONNAX parts to make it more reliable. No it works a little bit rougher through gear changes, but thats okay. And we put a bypass in the gearbox cooling system to keep it cooler, which helps the "rougher" too. ;-) In the transfer case the fork broke, so we could only drive in low gear. Wasn't a big deal to repair, but we had to bring the PW over 3000miles on the trailer back home which sucks...

So for me the torque of the cummins would be great and I know about driving short distances with such a big diesel motor. I am driving an old 44000lbs military semi 12.7l , so I am used to it. Better said I love it.

Please support me with your experiences - I am looking for doing minimum 300k miles with it by doing all services which wold be necessary.
By the way: How are your mpg's with light trailers in the mountains?

The key points would be:

- 5.9 oder 6.7?
- Automatic or G56 oder something similar if available
- GEN 3, 4 or 5
- Spare parts availability for 5.9 and GEN 3 are still okay?


Thanks for your help guys and girls!

 

[06 Dodge]

IMHO Gen 3, 2004.5, 2005 or 2006 with the Cummins 5.9l, your choice of either a well built Goerend auto RE48 or its equal or G56 manual, rear gear axel choice for climbing steep hills would be 4:10 or 4.88 if available, as for the early Gen 4 6.7l don't have any experience with it, its emissions system that I have read were not all that good and required $$ to repair but then if your not in the USA you could delete the emissions...

 

[truck2014]

IMHO Gen 3, 2004.5, 2005 or 2006 with the Cummins 5.9l, your choice of either a well built Goerend auto RE48 or its equal or G56 manual, rear gear axel choice for climbing steep hills would be 4:10 or 4.88 if available, as for the early Gen 4 6.7l don't have any experience with it, its emissions system that I have read were not all that good and required $$ to repair but then if your not in the USA you could delete the emissions...

The weights he is towing the Gen 4 6.7 with 3:42 gears will pull any hills he's talking about , ya emissions can be an issue . Mine has been pretty good 2014 6.7 Cummins 3500 68rfe 3:42 gears towing a 15,500 GVWR fifth wheel all over the mountain west without a problem.

I would get a 6.7 in any configuration long before I'd be getting a 5.9 .

 

[Ritchie_Rich]

2016 6.7 towed 14k fiver 7yrs over 10-12k passes no problem. Now tow 8k TT with the same results.
20-21mpg empty highway, 8-10mpg fiver, over 13.5mpg TT. Just don’t use it as a grocery getter.

 

[Ritchie_Rich]

Forgot to mention it’s a 68rfe and 3.42s.

 

[Dennis Shellito]

The 6.7L with the 68RFE trans is worlds better than the 5.9L with the 47 or 48RE transmissions. The only thing that tears a 68 trans up in my limited opinion is hotrodding, as the Cummins has way too much torque on the input. The 6.7s also come with an exhaust brake, and that is a big plus while towing. I too have taken a 5er over many mountain passes and on straight hiways I have had the cruise set on 75mph while doing so without a downshift from 6th gear, although my 11 6.7 Cummins has 3.73 axles under it.

 

[mtnrider]

6.7 all day long, preferably a 14+. The 4th gens are better trucks all the way around compared to the 3rd gens (I've owned them all).


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[Area 51]

6.7 all day long, preferably a 14+. The 4th gens are better trucks all the way around compared to the 3rd gens (I've owned them all).

Well, if we are going to spend money, let's just buy a brand new truck.
My neighbor just sold a Gen 2 for $14,000, in great shape, and would do all the towing he's talking about.
But sure, newer is better...except for the smog junk and cost.