Ram 2500 4x4 Cummins-opinions

[deerefan]

Earlier trucks, like the 2004 third gens, had 3.73s I think they kept that going until the 6.7 came out. Back in 2005 and 2006 a lot of guys were wanting 3.42 gears. And it actually worked sort of OK with the pre-emissions Rams.

The 3.42 ratio has worked fine for me so far. I believe the more aggressive trans gearing has allowed these rigs to work with 3.42 ratios.

 

[dodge man]

You could have a 2.00 rear end and if the tranny is geared to match it, it would be fine. I know my 2004 Cummins had a 4.10 rear end, which would have been great as long as it had one more gear in the transmission. It was only a 4 speed auto and it need on more over drive gear.

 

[heavy hammer]

I do thing my 05 with a six speed manual needs one or two more gears. I have the 4.10 in it and it drives great but could use a little more.

 

[deerefan]

I do thing my 05 with a six speed manual needs one or two more gears. I have the 4.10 in it and it drives great but could use a little more.

The only experience with a Cummins and a manual trans was a 2000 1 ton 2wd that belonged to a friend. I drove it helping him haul cattle to the scales. It was straight piped, had “rv” (I guess bigger??) injectors and either 4.11 or 4.56 gears. It had plenty of power. Honestly, it started my interest in Cummins, just took me 13 years to build my business up to the point of needing one.

 

[Raspy]

The 3.42 ratio has worked fine for me so far. I believe the more aggressive trans gearing has allowed these rigs to work with 3.42 ratios.

There is something to that. The third gens had the 48R trans. it had a 1st gear that was too high for proper towing and a 4th that was similar to what we have today. About .69 or so. The Aisin has a very low 1st that never strains for pulling power, sort of like a granny gear.

A significant difference is how the engine is tuned. The 5.9s, with a little tuning will pull from practically idle on up and do it aggressively. The 6.7 is so hobbled by its emission tuning that it needs to run a bit faster to build boost and to keep from downshifting.

The problem with the 3.42 gears is that 6th will not pull anything because it is running too slow to build boost. As soon as you want power, it has to downshift. High altitude or pulling a moderate trailer pretty much disables 6th gear. Even a head wind or the slightest grade. I have run for many hours in 5th and even 4th, just to keep it from hunting. The only time it felt, more or less OK, was at sea level and with no load in the truck and not towing.

Now, with the 4.10 gears, 6th becomes a useful gear. It will build boost and pull grades or pass if done with careful throttle use. Of course, mine is also deleted and mildly tuned.

Other differences that are nice are the more aggressive engine brake, lower gearing from a standstill that, under normal driving, makes the truck more peppy. The Aisin, which can't be tuned, likes the gearing better and shifts better. So, the bottom line is better drivability, better shifting, better braking and more useful gears, since 6th was mostly useless if doing any work. The noticeable seat-of-the-pants engine feel is that now, the top gear is between what 5th and 6th was before. 6th is a little higher than the old 5th was. With my 295/70r18 tires I'm right at 1800 RPM at 70. Cummins wants the engine running at a minimum of about 1800 while working and it will build about 26 PSI boost quickly if asked. I doubt any of this will have a bad affect on mileage because I was using 4th and 5th most of the time before.

Manufacturers tend to gear vehicles too high for my liking and I've geared down a number of times. Without fail, every one of those trucks drove better.

When comparing with the 3.73 gears in the 3rd gens, remember too, those trucks came with 265/70r17 tires. Now the stock tire is a 275/70r18 with about 29 revolutions less per mile. They put in higher gears and larger diameter tires for a big overall change in gearing.

 

[Monster5601]

The Aisin has a very low 1st that never strains for pulling power, sort of like a granny gear.

The 6.7 is so hobbled by its emission tuning that it needs to run a bit faster to build boost and to keep from downshifting.

The problem with the 3.42 gears is that 6th will not pull anything because it is running too slow to build boost. As soon as you want power, it has to downshift. Even a head wind or the slightest grade.

The Aisin, which can't be tuned, likes the gearing better and shifts better.

Cummins wants the engine running at a minimum of about 1800 while working

The Aisin's first gear is 3.75, the 68RFE is 3.23, and the 48RE was 2:45.

Beginning with 2013 RAM Cummins production, emissions were removed from the engine (with exception of EGR which is used sparingly) was move downstream into the exhaust. Engine tuning moved back to efficiency and performance.

I run a 2015 3500 RAM Cummins, SRW, 68RFE with 3:42s often pulling 15,000 pounds of RV. When I pull I use tow/haul mode and never experienced a lack of power or gear hunting. The truck cruises in fifth gear up to about 63 MPH then it drops to sixth gear. Head winds do not change the gearing albeit the strongest headwinds I've driven into were running in the low 30 MPH range. Reasonable inclines do not cause a downshift just a higher boost.

As far as the performance of the Aisin, you may want to see the posting over on the Cummins forum, seems the Aisin have more complaints than the 68RFE.

The RPM range is best determined by running Cummins PowerSpec program. Based on your gearing, payloads and towing weights, PowerSpec will recommend the proper RPM range. For my RV towing, PowerSpec recommended an RPM range between 1,600 to 2,200 RPM. PowerSpec is free to download.

 

[deerefan]

Had a rough idle for a short time yesterday. Bought some Seafoam. What injector cleaners do you guys use?

 

[showcattle]

I use PowerService or Seafoam. I also periodically add 8 oz of 2 cycle oil to a full tank of fuel. I can actually hear a difference.

 

[sw99]

I run Power Service in every tank - Diesel Kleen +cetane boost silver bottle in the summer and white bottle in the winter.

 

[Raspy]

The Aisin's first gear is 3.75, the 68RFE is 3.23, and the 48RE was 2:45.

Beginning with 2013 RAM Cummins production, emissions were removed from the engine (with exception of EGR which is used sparingly) was move downstream into the exhaust. Engine tuning moved back to efficiency and performance.

I run a 2015 3500 RAM Cummins, SRW, 68RFE with 3:42s often pulling 15,000 pounds of RV. When I pull I use tow/haul mode and never experienced a lack of power or gear hunting. The truck cruises in fifth gear up to about 63 MPH then it drops to sixth gear. Head winds do not change the gearing albeit the strongest headwinds I've driven into were running in the low 30 MPH range. Reasonable inclines do not cause a downshift just a higher boost.

As far as the performance of the Aisin, you may want to see the posting over on the Cummins forum, seems the Aisin have more complaints than the 68RFE.

The RPM range is best determined by running Cummins PowerSpec program. Based on your gearing, payloads and towing weights, PowerSpec will recommend the proper RPM range. For my RV towing, PowerSpec recommended an RPM range between 1,600 to 2,200 RPM. PowerSpec is free to download.

Well, sorta

It seems that starting in 2013 Cummins made the throttle response painfully slow to prevent smoke and reduce re-gens. Some of the emission control is in the exhaust, some of it is in tuning, some is in combustion chamber design and some is EGR. In 2013 with the addition of DEF, they were able to go back to the 2003 and early 2004 combustion chamber design that is more efficient, then use an after treatment to keep it clean while getting better mileage than the 2012 and earlier 6.7s that held out as long as possible before going to DEF. And they tuned them to not pull very well below 1600 RPM. That's OK, but the gearing and the tranny tuning meant that the truck spends a lot of time in the 1350- 1500 RPM range, by design. This can be overcome with Tow/Haul, or blocking out 6th, but it's a pain in real world driving. Once up a bit in RPM, and given a few seconds to build boost and fuel accordingly, they pull like a locomotive. This is not about a lack of power, it's about tuning or engine manners. There have been a lot of complaints since 2013 about throttle response.

It makes no difference to me how many people complain about the Aisin. I certainly am not going to change a trans because others may complain about theirs. The Aisin is an extremely robust tranny with an incredible torque converter. A real tool for heavy work with a deep 1st gear for getting loads moving effortlessly or for four wheeling. The problem is never whether it can handle the power, it's how it shifts based on it's map that is anticipating engine torque. It is not programmable, like the 68RE, and therefore the owner must tune the engine and gearing to work with the tranny. I've been discussing tranny and tuning issues on Cummins Forum since 2003, always looking for the best compromises. If you can't get the latest 4th gens up to at least 1600 RPM while towing, they are not going to respond well and that speed is somewhere north of 70 with stock gearing and 34-35" tires. Which means poor drivability or 5th gear most of the time, or even fourth in the mountains on grades. It doesn't take a Power-Spec program to tell someone where the engine is happy as the Cummins is a very easy engine to read. 1600-2200 is the natural full range it likes. 1800-2000 is the real sweet spot for hard work. 1600 is a good all day cruising RPM with light loads. Keeping it slightly higher in its RPM range while working hard also cools it better with faster and more even coolant flow. Plus, the locomotive roar is intoxicating at about 2000 RPM.

I've addressed the issues by deleting and tuning the engine to work well with the tranny. This means better throttle response and more power, while staying within reason for cool exhaust and good shifting. Some timing and no EGR, for efficiency. Then re-gearing to 4.10 for improved drivability, more useful gears and better engine braking. It puts the RPM where it is most useful at about 1600 at 60, 1800 at 70. It never needs to run faster than 2200, but will sometimes while braking where it's puts out about 150 HP in retarding force. The result is immediate throttle response, full boost quickly and no downshifting unless I give it full throttle. It loves to pass on grades while towing. With the 3.42 gears it was annoying to drive unless 6th was locked out when towing or at high altitude in the mountains. Part of this is caused by 34.3" tires that rotate about 29 times less per miles than the stock tires.

I chose the Aisin because I had put up with a 46RH and a 48RE for 400,000 miles and was tired of their nature. During that period though, the Cummins tuning meant instant throttle response from an idle on up. The consideration was to not pull too hard or the tranny would either overheat because of it's lockup strategy, or slip the lockup clutch. But the engine was always ready to go. The Aisin is designed to hold about 50% more torque than the engine can produce stock or with mild tunes, and it runs cooler than the engine oil because of it's lockup strategy. Now, with about 150,000 on the clock on my 2014, the only tuning issue related to the tranny is getting the shift completed under load, that is where proper tuning is important. Then it will take whatever the Cummins can dish out unless your talking about cranking huge HP numbers into it. No matter how hard mine gets worked, when changing the fluid, it comes out looking fresh and red with no visible metal in suspension.

After tuning and gearing, I can lean into it from about 60 MPH and it will respond with boost and power without having to wait for it to think about it, then decide to downshift, then slowly ramp the fuel to avoid smoke. When unloaded it is very responsive and eager to go. Shifting is better because of the lower gears. And now it has 6 working gears that can all be used most of the time. Mileage seems to be unaffected and it makes no visible smoke that I can see while driving. Excellent.