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Open Roads Forum  >  Fifth-Wheels

 > Ford super duty 3.31 rear end. Will it be a big mistake. ?

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cummins2014

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Posted: 01/30/21 03:56pm Link  |  Quote  |  Print  |  Notify Moderator

Lantley wrote:

4x4ord wrote:

Lantley wrote:

I 'll take slightly better over slightly worse every time.
I'm not sure why some feel the need to go through a lot of mumbo jumbo and tech speak to reach the slightly better conclusion.
The higher ratio will always tow better.
3.31 and 3.55 are pretty close to start with but the higher ratio still performs better when towing. Calculating a performance standard that uses 30" tires is misguided and misleading. Very few are towing RV's with 30+" tires


Consider this: To get your trailer moving your current truck starts out in 1st gear and with 3.73 rear gears the 910 lbft of engine torque is multiplied:

3.73 x 3.094 = 11.54 times giving you potentially 910 x 11.54 = 10,500 lbft to the rear wheels.p

The torque to the rear wheels of the new Ford with its ten speed transmission and a 3.31 rear end looks something like this
3.31 x 4.615 = 15.28 which could potentially put 15.28 x 1050 = 16,044 lbft of torque to the rear axle.

To get 16,044 lbft of torque to the rear axle of your 2019 GM you would need a 5.70:1 rear end.

My point is that 3.31 gears with a ten speed is far more than slightly better than what you are used to. When we are only pulling 16,000 to 18,000 lb rvs 16,000 lbft of torque is tremendous. Having 10 gears to choose from is really kind of over kill while pulling loads that the SRW trucks are capable of. Realize that 9th with 3.31 final drive is near identical to 10th with 3.55 gears. So the 3.31 equipped truck has tremendous capability to get our relatively light trailers moving in 1st gear, has more than enough gears to keep the engine at it's peak operating range while towing heavy or in the hills and has a 10th gear that can be utilized for optimum fuel economy when towing on flat ground or not towing. People are free to choose a 3.55 gear ratio for their SRW diesel and they will be happy but they are giving up a little economy to gain nothing.

You may have a point in terms of getting things rolling. There were a few Dodge guys complaining their Cummins were a bit lacking when it came to getting started a few few years ago. Maybe 2014 model years, I not that familiar with Ram trucks.
But overall I'm less concerned about getting things rolling vs. climbing the grade.
I never wished I had pulled away from that light faster, But I will always want more power climbing the grade.


Having the 2014 Cummins ,I’m not one of them complaining, now if I still owned my 7.3 Powerstroke I would be . I have yet to climb a grade with this 6.7 Cummins towing a 38’ and 35’ fifth wheel here in the mountain west wishing I had more power . Nor have I even thought about how fast I start from a light . Guess you have to have a Ford first before you have a Cummins [emoticon]

GIB2

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Posted: 01/30/21 04:24pm Link  |  Quote  |  Print  |  Notify Moderator

Nobody is speaking about tow haul & heavy loads. My 2020 GM 10 speed has almost identical gear ratios in every gear to Ford . Although I have no Ford manual to read ,my GM manual claims that it will not go beyond 7th gear in tow haul. I would expect Ford the same. One thing I know for sure they all blow the doors off semis in the mountains pulling 20,000 lb. load.

Lantley

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Posted: 01/30/21 04:34pm Link  |  Quote  |  Print  |  Notify Moderator

GIB2 wrote:

Nobody is speaking about tow haul & heavy loads. My 2020 GM 10 speed has almost identical gear ratios in every gear to Ford . Although I have no Ford manual to read ,my GM manual claims that it will not go beyond 7th gear in tow haul. I would expect Ford the same. One thing I know for sure they all blow the doors off semis in the mountains pulling 20,000 lb. load.

That's interesting the 10 speeds become 7 speeds when towing[emoticon]
I'm liking my 6 speed even more now.


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Posted: 01/30/21 05:37pm Link  |  Quote  |  Print  |  Notify Moderator

cummins2014 wrote:

StirCrazy wrote:

blofgren wrote:



If you Ford guys towed with a Cummins you would be absolutely amazed.....I usually have to give my truck some throttle when descending BC passes when pulling my 16k fiver loaded for a 3 week trip. And no cruise control or automatic braking of the service brakes.


but then we would be seen in a Dodge [emoticon] when I bought my 2014 (in 2016) I tried out all the big three, dodge was actoula on the bottom of my list. rode rouch, and felt very enimic driving around town. I am sure it pulls like a freight train but it just wasnt a fun or nice driving experiance to me.

the biggest thing is the fords never had an "exhaust brake" untill the 2015 model, before then it was just using the VV turbo which works but not near as good as a real exhaust brake. My VVT will hold 14000lbs of 5th wheel going down the coq and I only have to tap the brakes two or three times at the big hill before the tunnels traveling from kamloops to van. my buddy has a 2017 and a bit heavier of a trailer and he sets his cruise and doesnt touch his brakes all the way unless trafic is slower.

Steve



There is no tapping brakes with a Cummins , and I am towing the same weight . I spend nearly 16 years in a Ford Superduty, I know all about them ,they are okay, they got nothing on the Cummins .


except for more torque, more HP and a way better auto tranny ...

that is with mine that doesnt have a engine brake. newer ones do so same as the dodge no tapping brakes.


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4x4ord

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Posted: 01/30/21 07:38pm Link  |  Quote  |  Print  |  Notify Moderator

cummins2014 wrote:

I have yet to climb a grade with this 6.7 Cummins towing a 38’ and 35’ fifth wheel here in the mountain west wishing I had more power [emoticon]


But,... there have likely been plenty of people behind you wishing you had more power.[emoticon]


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Lynnmor

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Posted: 01/31/21 07:34am Link  |  Quote  |  Print  |  Notify Moderator

cummins2014 wrote:

Lynnmor wrote:

cummins2014 wrote:



There is no tapping brakes with a Cummins , and I am towing the same weight . I spend nearly 16 years in a Ford Superduty, I know all about them ,they are okay, they got nothing on the Cummins .


Perhaps you never owned a 6.7 Ford diesel or didn't drive one enough to appreciate how they work. Since my rear tires wear faster than the front now, I don't want a pair of tires doing even more work. Yes, I know you have more tires than me. Would sliding the rear tires to slow down satisfy your need for considerable exhaust braking?


You lost me on whatever you are trying to say . I only have four tires . My comment was simple the Cummins is second to none as far as how well the exhaust brake works, if the Ford now works as well , that’s great . As far as the Fords go there was a day the exhaust brake on their Powerstroke was non existent, I’m sure they have improved .


You do understand that all the braking from an exhaust brake is done thru the rear wheels of the truck? That heavy truck and trailer is pushing on those two tires, and everything else is going along for the ride.

All 6.7 Fords had exhaust braking as claimed, previous engines had none and there was no claim that they did. Yes, later models had more braking and a button to play with.





cummins2014

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Posted: 01/31/21 08:00am Link  |  Quote  |  Print  |  Notify Moderator

Lynnmor wrote:



You do understand that all the braking from an exhaust brake is done thru the rear wheels of the truck? That heavy truck and trailer is pushing on those two tires, and everything else is going along for the ride.

All 6.7 Fords had exhaust braking as claimed, previous engines had none and there was no claim that they did. Yes, later models had more braking and a button to play with.



I understad all you are saying ,just didn't get you saying I have more tires then me. I have a SRW 3500 Ram Cummins . As said yes ,Ford had no exhaust brake in the earlier Powerstrokes, I am aware of them having one one now , have read many times ,they were no where near as effective as the Cummins , it sounds like they have finally caught up , which is great. I know the benefit of having a good exhaust brake while towing. , or anytime . I run with tow haul ,and exhaust brake on regardless of what I am doing, unless there are slick roads .

Its good to hear the Ford has caught up with a effective exhaust brake ,my son has a new 2021 on order, and plans to be towing a fifth wheel.

* This post was edited 01/31/21 09:20am by an administrator/moderator *

cummins2014

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Posted: 01/31/21 08:05am Link  |  Quote  |  Print  |  Notify Moderator

4x4ord wrote:

cummins2014 wrote:

I have yet to climb a grade with this 6.7 Cummins towing a 38’ and 35’ fifth wheel here in the mountain west wishing I had more power [emoticon]


But,... there have likely been plenty of people behind you wishing you had more power.[emoticon]



You got that right , I got stuck behind a couple Fords last time out , I would of shown them the power , but the darn 2 lane roads [emoticon]

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Posted: 01/31/21 08:19am Link  |  Quote  |  Print  |  Notify Moderator

cummins2014 wrote:




I understad all you are saying ,just didn't get you saying I have more tires then me. I have a SRW 3500 Ram Cummins . As said yes ,Ford had no exhaust brake in the earlier Powerstrokes, I am aware of them having one one now , have read many times ,they were no where near as effective as the Cummins , it sounds like they have finally caught up , which is great. I know the benefit of having a good exhaust brake while towing. , or anytime . I run with tow haul ,and exhaust brake on regardless of what I am doing, unless there are slick roads .

Its good to hear the Ford has caught up with a effective exhaust brake ,my son has a new 2021 on order, and plans to be towing a fifth wheel.



People who have run both the new Powestroke and Cummins claim the Cummins has a stronger exhaust brake. I think you need higher engine rpm with the Powerstroke to get the same measure of braking as the Ram. However the 10 speed can be used to give you that higher rpm.

* This post was edited 01/31/21 09:22am by an administrator/moderator *

cummins2014

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Posted: 01/31/21 08:57am Link  |  Quote  |  Print  |  Notify Moderator

Its sounding like the Powerstroke is catching up. As said my sons got one coming. He is a blue Koolaid guy, me I have had them all. This Ram I have has done well. To be honest I loved my old 7.3 . If it had the power I needed for the bigger fifth wheel I had , I most likely would still have it. I am far from a new truck every year guy. I had it nearly 16 years , it had low miles 130K , looked like new when I sold it ,have seen it around town a couple times since .

I don't usually get into these truck debates , first off I don't know that much about a lot of the stuff about them. I do all my own maintenance , all the fluids ,brakes etc. I know how to take care of them ,and thats what is important to me . I have found with the exhaust brake on this Cummins ,as said it works best on cruise control ,letting it do its thing , I am usually off ,and on the throttle if I don't use cruise control . The shorter grades its alright , but the long grade ,and no sharp turns ,cruise control ,and let it do its thing .

If you have ever come down to Bull Head City in Arizona from Las Vegas ,that is a long hill that you would really appreciate good exhaust braking , and using cruise control .

* This post was edited 01/31/21 09:23am by an administrator/moderator *

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