3:73 to 4:10 cost

[jaflowers]

Just too bad there wasn't the Aisin option on the standard 3/4 tons. 4.44 gears would have been about perfect for most anything.

 

[ppine]

The simple answer is a lighter trailer.
You do not have enough truck for the hills. Changing out the gear ratios will make a difference, but not as much as you are hoping for.

 

[JerryETX]

The simple answer is a lighter trailer.
You do not have enough truck for the hills. Changing out the gear ratios will make a difference, but not as much as you are hoping for.

Simple? That's an assumption on your part at least in my case.

 

[SouthTexan]

The unfortunate thing is that while shorter rear gears will give you more torque to the wheels, it will not give you more horsepower which is what dictates how fast you can go. The 6.4L does have a lot of horsepower, but like most N/A engines you don't a lot of it at rpms down low where you normally drive like diesels or gas turbo charged engines do. Adding 4.10s will not put you in that much higher of rpm to make substantially more horsepower. I haven't seen the dyno, but your 6.4L is likely making around 150 hp under 1,700 rpm while a diesel is making around 300 hp under at 1,700.

I honestly think taking out 5th and 6th gear(and possibly 4th) might be the solution if you want to travel at 70 mph towing your trailer. It would be better if you can swap your 66RFE for a 8HP75 found in the newer models.

 

[Dean2]

Low rpm torque is one of the really great features of my V10 2500. it produces max torque at about 1800 rpm. Pulls like a diesel without the headaches of diesel.

 

[SouthTexan]

From the engine dyno released by Dodge back in the day, the 8.0L V10 does put down more torque and therefore more horsepower of around 250 hp at 1,700 rpm than the 6.4L. Max torque of the 8.0L was 450 lb-ft at 2,400 rpm which is really low for a N/A gas engine. Torque generates horsepower and horsepower dictates your speed. If you have more low end torque, then you have more low end horsepower.



The current standard output Cummins is 275 hp and HO Cummins is 348 hp at 1,700 rpm doing the math of their peak torque.

 

[06 Dodge]

I believe the current Cummins HP/TQ numbers for the 2022 SO is 370/850, the HO 420/1075, I recall they reach max TQ at around 1700/1800 RPM's with max HP around 2800.

 

[SouthTexan]

Correct as far as peak HP and RPM, although I forgot the HO has torque of 1,800. That changes the amount of HP generated at peak torque. I was just doing the math on the HP these two generate at peak torque.

(Torque X RPM) / 5,252 = HP at said RPM

(850 lb-ft X 1,700 rpm) / 5,252 = 275 hp at 1,700 rpm

(1,075 lb-ft X 1,800 rpm) / 5,252 = 368 HP at 1,800 rpm

For the 370 hp Cummins, that is enough HP to tow a 12k trailer up around a 3% grade at 70 mph at 1,700 rpm peak torque. The HO could tow the same 12k trailer up around a 6% grade at 70 mph at it's peak torque of 1,800 rpm. Keep in mind that the chart below calculates for an average amount of wind resistance. If an engine is only generating around 150 HP at this RPM, then it will need to downshift until it is at an RPM with high enough HP to go 70 mph at X grade. If it cannot make enough HP then it will drop speed to match the amount of HP it has available.

Gear multiplication by changing rear gears for a shorter ratio will not help much for wanting to keep a certain speed while towing. Downshifting to an RPM where you make more HP will.

EDIT: Keep in mind that an N/A engine loses 3% of it's power for every 1k ft above elevation and a turbocharged engine lose between .5% to 1.5% per 1k ft depending on the turbo's efficiency and size.

 

[ppine]

What diesel headaches?

 

[JerryETX]

The unfortunate thing is that while shorter rear gears will give you more torque to the wheels, it will not give you more horsepower which is what dictates how fast you can go. The 6.4L does have a lot of horsepower, but like most N/A engines you don't a lot of it at rpms down low where you normally drive like diesels or gas turbo charged engines do. Adding 4.10s will not put you in that much higher of rpm to make substantially more horsepower. I haven't seen the dyno, but your 6.4L is likely making around 150 hp under 1,700 rpm while a diesel is making around 300 hp under at 1,700.

I honestly think taking out 5th and 6th gear(and possibly 4th) might be the solution if you want to travel at 70 mph towing your trailer. It would be better if you can swap your 66RFE for a 8HP75 found in the newer models.


View attachment 505506

So yesterday I pulled our TT this past weekend home from the RV park we kept it at. Trip was about 200 miles. I learned my truck does A LOT better when I’m not fighting a high wind. I’ve pulled our TT 3 other times and all 3 times the wind was blowing at least 15 and up to 25 mph. Yesterday I kept it in 4th gear and was an to hold 68-70 with no issues at least on flat highway. Obviously hills slowed me down some but on this trip there weren’t any steep hills just rolling hills. Weighed the rig at a Cat Scale and it was heavier than I thought at 10,300. My total gross combined weight was 18180. Curb weight of the truck is about 6900 which means I had about 800 pounds of stuff in the bed and cab including me and my wife which was half of that weight (this didn’t include tongue weight). I was pleased the way it pulled. I just have to stay away from the wind which along the Texas coast where we go is pretty hard to do.

 

[GsRAM]

Good deal, glad to hear you had a better experience. When I tow with mine I engage tow/haul mode, disable the rear park sensors and then when I'm in gear, I manually select 5th gear, so that 6th is locked out (I think tow/haul does that also anyway) but also so MDS is deactivated while I'm towing so all 8 cylinders stay lit all the time. I dont feel, personally, having cylinders go out when towing heavy loads is good for the truck mechanically, but also from a performance standpoint. There are other opinions on this and that's ok, I do what makes sense to me based on my background and experience.

My truck has always been more responsive with the throttle and trans shifting when I manually select a gear so mds is deactivated. It helps a lot towing and just in general driving. In my experience, shutting off mds made no appreciable difference in fuel mileage either. Just my .02.

 

[Irishthreeper]

^^
Tow haul prevents MDS from activating

 

[CheechDogg.0n37s]

^^
Tow haul prevents MDS from activating

Not on my truck .... is this just an HD 2500 and up thing? I know you could turn it off with tow haul in the past even on 1500s from what I have read on the forums, but on the 1500s with the 8speed like mine, nope doesn't work ...

 

[Irishthreeper]

I had a ‘19 DT 1500 and now a ‘21 2500. Tow/haul blocked MDS on both

 

[CheechDogg.0n37s]

I had a ‘19 DT 1500 and now a ‘21 2500. Tow/haul blocked MDS on both

Well then waddafawk! lol ..... I though tow haul didn't disable MDS anymore ... I must be stuck on an old thread or something in my head lol ..

Good to know though, pretty cool that it does that now ...

Thought I read that tow/haul on 2018 RAm 1500 just locks out 8th and you can only go as high as 7th gear unless you floor it ....

 

[2020PW]

If your gonna do it go 4:56

 

[JerryETX]

If your gonna do it go 4:56

Did you go this route?

 

[2020PW]

Did you go this route?

No have 4:10 want 4:56

 

[Dean2]

Manual gear selection or tow haul mode will both individually disable MDS.

 

[jambbii]

Figured I'd chime in with my 2 cents. 18 Power Wagon on 35s. 19,500lbs loaded (4.10s Factory/5.38 regear)

I could pull 6% grades in second gear (4.10s) around 55mph with factory 33s or whatever they were.. in second gear (4500 rpm)

I regeared and now run 35"M/T muds and 5.38s. Same hills 3rd gear at 55 no problem (probably around 4000 rpm)

I'm in Az and we literally go from 1000 ft about sea level to 7700 in and hour and a half and most of these lower hills it's 100 plus degrees out. Something unexpected when regearing is the engine braking better down hills as well. The RFE shifts like it should...

I have my 4.10s still if you are interested.