Getting ready to move up to a 3500. I've shopped the available trucks, and have a good idea of what I want. The two I have narrowed down to are a '14 and a '15 Ram 3500. Identical with the exception of the rear axle ratio. One has the 3:73s and the other has 4:10s. I'll be towing a 5th wheel in the 18-20K range fully loaded,and by the spec sheets, both will do the job. I'll be running empty a lot, which way would you go?

I assume both are duallies?Get the 4.10 rear end. You wont regret it.

second vote for 4:10. worth it.You can Thank Us later.

For a trailer in the 18 to 20K range I would go with the 4:10's over the 3:73's.JMHO

rear axle gear ratio | Good Sam Community

IdaD
Explorer
Nov 27, 2016
I have a 2500 so it's got 3.42s, but I actually really like it and I don't see why you'd need to bump it up unless you have a very heavy combined load. To me having 6 speeds really helps make the lower ratios work well when you consider both towing and non-towing performance.

I just ran across southern Idaho both directions for the holidays and had the truck loaded down with two adults, three kids, one labradoodle and way more "stuff" than you'd think necessary for a few days away. With the cruise set at 83 the truck just idles along at about 1800 RPM and never downshifts even on some pretty sizable grades into headwinds. Very nice freeway cruising truck. Also considering the temperature, speed, terrain and wind, I was very pleased to get close to 18 MPG.

Obviously there's a tradeoff when towing and with the weights OP is considering a lower ratio probably makes sense, but for somewhat lighter trailers there are some significant advantages to getting the lower ratios. Just throwing out some food for thought.
burningman
Explorer II
Nov 27, 2016
Well, in fact it is possible to lug an automatic. If you've done like I have and upgraded your auto trans to fully built, billet-everything bulletproof specs which includes the ability to manually lock the torque converter, it is possible to lug it.
Also, if your '02 Cummins hasn't got enough power, you don't need a whole new truck.
Do a few simple things like installing a wire-tap tuner and bigger injectors and it will run right with the new ones. The basic engine in your truck is just as stout as any. It's all about the fuel system.
If you have a Cummins and you want more power, it's there for the taking.
blofgren
Explorer
Nov 20, 2016
rhagfo wrote:
blofgren wrote:
With my manual transmission equipped Cummins, I simply see if it will pick up speed in whatever gear I'm in. If it does, then I don't consider it to be lugging. And it will happily tow my 16k high profile fiver on level ground at 1,500 rpm with no problem at all.

Too many gassers, shifting to diesel and don't understand how they work!
Diesel don't need to be screaming at higher rpm to provide power, they are designed to run at lower RPM.
I tow in the flats in OD, and at 60 or never have issues accelerating without down shifting. When I come to a noticeable hill I will drop one gear to 4th, and climb at about 2,000 rpm.
Even at idle I have 40 to 50 psi of oil pressure.

Exactly. I tow the vast majority of time in 6th gear and this includes moderate rolling grades. When I approach a larger grade I will perform a relaxed downshift into 5th gear which will bring it up to 2,200-2,300 rpm which will suffice on most grades. It is only on extreme mountain passes that I need to go down another gear to 4th. And my oil pressure is right where yours is.

I'm very happy with my 3.73 gears because it provides a great ratio for both towing and solo driving. My previous 2 trucks were 4.10 which were great for towing but suffered in solo driving with increased rpm which equates to more noise and burning more fuel. Certainly a necessity for towing very heavy but not for most IMHO.
4x4ord
Explorer III
Nov 19, 2016
Huntindog wrote:
On every motor I have rebuilt the rod bearings were egg shaped... The piston side well into the copper. This is what happens when the lubrication film breaks down. Eventually it will cause the death rattle of a rod knock.

Lower oil pressure is NOT a solution.

Your motor, your choice.

Yup eventually.....after about 1 million miles on the Cummins. So rev er up a little, fuel is cheap.??
Huntindog
Explorer
Nov 19, 2016
On every motor I have rebuilt the rod bearings were egg shaped... The piston side well into the copper. This is what happens when the lubrication film breaks down. Eventually it will cause the death rattle of a rod knock.

Lower oil pressure is NOT a solution.

Your motor, your choice.
4x4ord
Explorer III
Nov 19, 2016
The oil pressure gauge in the Ram is actually more of an idiot light. So long as oil pressure is above 6 psi the ECM will determine what pressure to display on the gauge based on rpm and temperature. Ford doesn't have an oil pressure gauge.
Turtle_n_Peeps
Explorer
Nov 19, 2016
Huntindog wrote:
Turtle n Peeps wrote:

#2. Ever hear of variable displacement oil pumps?
Sure. But the Cummins doesn't use such a pump.

So I am not sure why you are bringing it up.

Because the Cummins doesn't need such a pump. The Cummins, like many engines, put out WAY more oil pressure than needed. The by-pass is always in play. My point is many manufactures are learning that you don't need a ton of oil pressure to make bearings happy. Spec on my 6.5 is 15 PSI at idle and I'm sure the Cummins is close to that also.

As far as hard on an engine or wearing an engine out sooner; that's just being silly. Technically correct, but silly. Much like me saying I took a leak in the ocean so now it's more full. :B

You and I both know that 80 to 90% of engine wear is caused by cold starts. At least I do anyway. Many, many studies have shown this.

If one is really that concerned about engine wear you should concentrate on the big picture of cold starts and less about RPM. Besides like I said; you can't lug any modern truck with an automatic.
mowermech
Explorer
Nov 19, 2016
Since I once had an older (1994) Dodge Ram 3500 dually CTD, manual transmission (5 speed) with the 4.10 rear end, I can speak from some experience. The truck was set up to tow a fifth wheel, and the Gross Combined Weight was 21,800 lbs. When going up a steep pass (Homestake in Montana, Donner in NV/CA, Vantage Hill in WA, etc.) I often had to shift down to 4th to keep the pre-turbo EGT below 1300.
When not towing, I often wished for a higher rear end ratio, 3.73 or even 3.54.

The truck I have now (see sig.) has 3.54 gears, and I love it. It tows my 7X14 box trailer with two ATVs aboard no problem at all! However, I do wish it had an exhaust brake. The old '94 did, and it was great whether towing or not.
If I had to make the OP's choice, I would go for the 3.73 gears.
rhagfo
Explorer III
Nov 19, 2016
blofgren wrote:
With my manual transmission equipped Cummins, I simply see if it will pick up speed in whatever gear I'm in. If it does, then I don't consider it to be lugging. And it will happily tow my 16k high profile fiver on level ground at 1,500 rpm with no problem at all.

Too many gassers, shifting to diesel and don't understand how they work!
Diesel don't need to be screaming at higher rpm to provide power, they are designed to run at lower RPM.
I tow in the flats in OD, and at 60 or never have issues accelerating without down shifting. When I come to a noticeable hill I will drop one gear to 4th, and climb at about 2,000 rpm.
Even at idle I have 40 to 50 psi of oil pressure.
Huntindog
Explorer
Nov 19, 2016
Turtle n Peeps wrote:

#2. Ever hear of variable displacement oil pumps?
Sure. But the Cummins doesn't use such a pump.

So I am not sure why you are bringing it up.