Dodge cummins 5.9 or 6.7 ?

[Kennedycamper]

I'm looking to buy a newer truck for hauling a 5th wheel. For those who have had both 5.9 & 6.7 engines, which do you think is better and why? Right now I'm leaning towards the 5.9, because it has a lot less pollution **** on it. Truck will probably be a 2005 to 2009. Opinions?

[Kennedycamper]

OP here, Wow I didn't know this thread went on this long. I just read the last 6 pages I hadn't seen before. I did buy a new truck. I ran into a great deal on a 2009 3500 dually. I will be doing the deletes soon, but keeping the stuff in case I need to get it smog checked at a later date. It is a much more comfortable drive than the 01 2500 I had.

[Greene728]

IdaD wrote:
The vast bulk of the failures on the 68RFE I've seen reported have involved tuned trucks. Leave the power stock and it seems to perform pretty reliably. I don't have any issues with the way mine shifts, unloaded or with a trailer in tow.

Start tuning and maybe it is weaker than the others. I find stock power more than adequate so I have no intention of finding out.

I completely agree!
Mine will remain stock until warranty is up for sure. Then stock until the day comes I have issues. Then address them accordingly.

[Cummins12V98]

up2nogood wrote:

Cummins12V98 wrote:

up2nogood wrote:

Bedlam wrote:
I think when GM started using the Allison around 2001 for its pickups, it made the others up their game. Ford brought out the 5R110 with the 6.0 PSD in 2003 and 6R140 with the 6.7 PSD in 2011 while Dodge held out until 2007 with the introduction of the 6.7 CTD and 68RFE (although still weak compared to the competition)and finally started using the Aisin in 2013.

Explain weak compared to the competition :h

I can personally attest to the 68RFE being a very capable trans. I sold my 2011 RAM Dually with 3:42 gears towing 28-29K combined and it never gave me an issue. Here is the pan at 65K just before I traded the truck. Fluid had about 50K.

I guess time will tell on the 68, no issues with mine so far.

Still waiting for an answer on what made the 48 such a great tranny. I was under the impression they were pretty troublesome .

In 03-07 the factory started taking note on what the aftermarket guys were doing to keep the 48 from falling apart and those years maintained held the power just fine. The 94-02's need to be upgraded if any power was added. At 100K I added a Banks PowerPack kit to my 98 12V and smoked right thru the torque converter. Upgraded upgraded the trans and worked well towing 20K+ with 300HP and 750TQ at the rear wheels.

[wilber1]

If I have any problem with the way my 68RFE shifts, it is that it waits too long before it shifts down when towing. I find that using the ERS to shift down earlier makes for much smoother operation. I also think the combination of Tow Haul and the EB can be too aggressive when descending grades. I switch Tow Haul off and use the ERS to control speed when descending long grades.

Other than that, I think it shifts just fine.

[cummins2014]

IdaD wrote:
The vast bulk of the failures on the 68RFE I've seen reported have involved tuned trucks. Leave the power stock and it seems to perform pretty reliably. I don't have any issues with the way mine shifts, unloaded or with a trailer in tow.

Start tuning and maybe it is weaker than the others. I find stock power more than adequate so I have no intention of finding out.

Have you tried it in cruise control on a downgrade, that seems the only time I get a bit rougher downshift when trying to hold the speed set on the cruise, but only with the weight of my fifth wheel. As said before all other situations its smooth down shifting.

Being that its supposedly a learning transmission, the downshifting on grades seem to be getting smoother as times goes on when towing.

[IdaD]

The vast bulk of the failures on the 68RFE I've seen reported have involved tuned trucks. Leave the power stock and it seems to perform pretty reliably. I don't have any issues with the way mine shifts, unloaded or with a trailer in tow.

Start tuning and maybe it is weaker than the others. I find stock power more than adequate so I have no intention of finding out.

[cummins2014]

mileshuff wrote:

up2nogood wrote:
Biggest complaint I hear about the 68 is the shifting. Have no idea what that actually means. Mine seems to shift fine. I get a little bit of a harsh downshift while towing in cruise control on a steep grade, and that seems to starting to smooth up. Other then that no complaints

My 2007 with 68RFE often downshifts VERY harsh if I have EB or T/H on. 3-2 downshift at low speeds slams gears beyond anything reasonable. Huge jolt. Once I exit highway I have to turn them both off. Dodge has a TSB to address this exact issue. Had that done back in 2007 but didn't solve the issue and Dodge would not do anything further. I've gotten used to it, just don't use E/B or T/H except on highways which is where they are needed the most. Otherwise its smooth. 92K miles and no trouble.

Its the cruise control downshifting to maintain the set speed on a downgrade when towing thats a bit harsh, otherwise towing on the flat it downshifts pretty smooth towing or empty.

[Mickey_D]

I have a 2014 2500 with the 68RFE and they do shift different than a gasser transmission, especially when not towing. Occasionally you can get a harsh shift, mostly if you quickly let off the throttle right when it wants to shift, but it is not bad. The annoying thing that it does is if you are running about 50 to 55 at about 1100rpm in 6th with no turbo boost, if you add throttle to accelerate, mine will down shift a gear or two, let the engine rev up and add boost (while not adding much acceleration), and then upshift back to 6th and then takeoff. With the 10K travel trailer or 14K equipment trailer behind it, the transmission actually seems happier and more relaxed. From looking at the forums, seems like most failures come from either abuse (hardcore mudding with giant tires) or on deleted and hot rodded trucks that are putting out a lot more than stock power.

[mileshuff]

up2nogood wrote:
Biggest complaint I hear about the 68 is the shifting. Have no idea what that actually means. Mine seems to shift fine. I get a little bit of a harsh downshift while towing in cruise control on a steep grade, and that seems to starting to smooth up. Other then that no complaints

My 2007 with 68RFE often downshifts VERY harsh if I have EB or T/H on. 3-2 downshift at low speeds slams gears beyond anything reasonable. Huge jolt. Once I exit highway I have to turn them both off. Dodge has a TSB to address this exact issue. Had that done back in 2007 but didn't solve the issue and Dodge would not do anything further. I've gotten used to it, just don't use E/B or T/H except on highways which is where they are needed the most. Otherwise its smooth. 92K miles and no trouble.

[cummins2014]

jus2shy wrote:

up2nogood wrote:

Bedlam wrote:
I think when GM started using the Allison around 2001 for its pickups, it made the others up their game. Ford brought out the 5R110 with the 6.0 PSD in 2003 and 6R140 with the 6.7 PSD in 2011 while Dodge held out until 2007 with the introduction of the 6.7 CTD and 68RFE (although still weak compared to the competition)and finally started using the Aisin in 2013.

Explain weak compared to the competition :h

Stock for stock, it doesn't have as much holding power as the other two transmissions. However, for our typical duty cycle for towing RV's and other typical trailers for a class 3 vehicle, it's adequate. The 68RFE (stock) is pretty much limited to 800 lbft of input as per RAM, which is why they don't offer a hotter tune stock for that transmission and why they went with the AS69RC Aisin transmission for the high output 3500's (which are pushing 900 lbft of torque at this moment). However, the 68RFE can be beefed up significantly to handle much more power as is the same case with other transmissions.

Thanks, I have been aware of that, I guess if I need 900 ft lbs, then I will have the aisin . There does not seem to be much more complaints about the 68 then the aisin on the cummins forum.

Biggest complaint I hear about the 68 is the shifting. Have no idea what that actually means. Mine seems to shift fine. I get a little bit of a harsh downshift while towing in cruise control on a steep grade, and that seems to starting to smooth up. Other then that no complaints

[Bedlam]

The Class 4 & 5 trucks run a detuned CTD, yet are exclusively Aisin or manual - Engine output is not the whole story why the 68RFE is not offered. I think the 68RFE only has enough capacity for the SRW's but the main reason is it sold is because it offers higher profits than an outsourced transmission.

My prediction is that Allison will now need to step up its transmission once the DM is upgraded. I don't think it can handle the torque of the competition.

[jus2shy]

up2nogood wrote:

Bedlam wrote:
I think when GM started using the Allison around 2001 for its pickups, it made the others up their game. Ford brought out the 5R110 with the 6.0 PSD in 2003 and 6R140 with the 6.7 PSD in 2011 while Dodge held out until 2007 with the introduction of the 6.7 CTD and 68RFE (although still weak compared to the competition)and finally started using the Aisin in 2013.

Explain weak compared to the competition :h

Stock for stock, it doesn't have as much holding power as the other two transmissions. However, for our typical duty cycle for towing RV's and other typical trailers for a class 3 vehicle, it's adequate. The 68RFE (stock) is pretty much limited to 800 lbft of input as per RAM, which is why they don't offer a hotter tune stock for that transmission and why they went with the AS69RC Aisin transmission for the high output 3500's (which are pushing 900 lbft of torque at this moment). However, the 68RFE can be beefed up significantly to handle much more power as is the same case with other transmissions.

[Grit_dog]

Did the op buy a truck yet?? 8 pages later.
Already said but I'd only get a 5.9 with a manual trans. The autos are ok but the gear splits on a 4 speed behind the Cummins are horrible.
The way used diesel truck prices are now I couldn't see buying a 5-10 year old one unless it was really a deal. It doesn't even take $10k extra to get an almost new '14 or '15 Tradesman CC Cummins over a late 3rd gen truck.
At the very least I'd drop the couple thousand more on an early 4th gen.

[Bedlam]

I thought the same Allison 1000 was used in the Kodiak C4500 and C5500. I know 2005 was the year it went from 5-speeds to six but little else changed. Class 6 was the Allison 2000.