Perceived difference between 3.73, 4.10 & 4.30 gears

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Back2PA

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As I'm looking at trrucks and towing capabilities, in some cases it varies with axle ratio. While I understand the basics of gearing I can't say that I have a sense of the difference in feel and drivability of say a 4.10 vs 3.73. It seems most trucks have the 3.73 gears, I assume because buyers were hoping for somewhat better mileage. Assuming a V10, questions:
  • How big of a difference in mileage would one typically see comparing the three gear ratios?
  • How much difference in perceived pulling power would one see between 3.73 and 4.10 (seems to be the two most common)? Is a 3.73 truck going to be a slug?
  • How much difference in descending hills? Noticeable loss in engine braking requiring 1st gear for example when it might not have been required? Still not enough in 1st when it might have been good with 4.10/4.30?
Again, I realize a 4.10 geared truck will be turning more RPMs for a given gear, just trying to get a sense of how big the difference is and how big a difference it makes towing a 5W.

These questions assume that the 5W would fall within the towing capabilities of a 3.73.

Thx
 

Frank B

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Are we talking diesel, or gas? All gearing systems trade engine RPM for rear wheel torque. Torque is the strong suit of diesels.


Is most of your Towing done in the mountains, or on the flat?  Are you in a hurry, or not? Will the lower gear ratio allow you to tow a unit bigger than what the truck really should be pulling?

The difference between 3. 73 and 4.10 is not that huge numerically. I just wonder why it makes a difference to you?
 

Rob&Deryl

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For selecting gear ratios, you need to have some goal in mind and know the power & torque curves of the engine.

If you have a very heavy rig (truck & trailer), 4:10 gears will help you get it rolling easier. The downside is you may be running much higher rpms on the highway which may lower mpg.

On a RAM diesel, for example, the heavy duty transmission (the Aisin), has a lower 1st gear to help with the start so may not need the 4:10s. Mine (a single rear wheel model) has 3:42 gears, shifts to 2nd before 10 mph and is only turning 1600 rpm at 75 mph. Empty I get 20mpg on the highway. Towing, you lock out 6th gear (in tow/haul mode it also changes the shift points) which brings the engine into its power band at 55-65 mph.
 

kdbgoat

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On the 2013 Ram 1500 I had, there was less than 2 mpg difference between 3:21 and 3:92 rear gears when not towing. I had the 6 speed, so the 3:92's made a big difference when accelerating from a stop when pulling what was a maximum load for that particular truck.
 

Back2PA

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Frank B said:
Are we talking diesel, or gas?

As I mentioned, this relates to a V10 (gas).
Frank B said:
Is most of your Towing done in the mountains, or on the flat?  Are you in a hurry, or not?

I anticipate most of the towing will be in East, on the flat. No one in a hurry should be driving/pulling an RV (IMO)

Frank B said:
Will the lower gear ratio allow you to tow a unit bigger than what the truck really should be pulling?

Also as mentioned, the questions assume the weights will fall within the limits of a 3.73. That said, the higher ratio does not "allow you to tow a unit bigger than what the truck really should be pulling" - using Ford's own towing numbers for a 2009 F-350 SRW CC for example, having 4.30 gears vs 4.10 adds 2000 pounds to the towing capability.
Frank B said:
I just wonder why it makes a difference to you?

That's the entire point of the question, to ask those who have experience with higher and lower geared trucks as to how they drove, how they pulled, and how much difference there was in mileage.

kdbgoat said:
On the 2013 Ram 1500 I had, there was less than 2 mpg difference between 3:21 and 3:92 rear gears when not towing. I had the 6 speed, so the 3:92's made a big difference when accelerating from a stop when pulling what was a maximum load for that particular truck.

Thx, that pretty much answers the MPG question. 2 may not seem like much, but that's about 16% improvement over anticipated MPG


 

Broke Boater

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If you want a truck to tow with, get a Diesel and a newer one with a least a 6sp auto tranny and a engine brake, jeez.,,,gregg
http://special-reports.pickuptrucks.com/king-of-beasts.html
 

blw2

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I can't answer the direct question.  It's been many years since my high school days when I was friends with some hot rod drivers and we were always tweaking, racing, etc... So I've lost sense of how to really explain or feel the differences.

that said, I think the way I'd look at it is to ask, "Where am I spending most of my time?"
I think that kinda points to where I'd want to focus the most improvement.  In an RV, mostly flat land...it's definitely the highway speeds where I spend most of my time..... not making quick starts, not climbing hills, not really digging in like a tractor....so I'd want lower ratio for better mileage and slower engine speeds

Now you've got me curious...I can't remember what the rear diff gearing is in my RV.  I'll have to look at that some day.....
not that it really matters to me all that much because my Rv seems maybe a bit slow off the line so that tells me I wouldn't want to go to a much lower ratio.... and it's fast enough and has enough power to get me going and climbing all the hills I've needed to....so I don't really need to go to a much higher ratio.....
 

jubileee

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I like the gearing to put me close to peak torque at the speed I like to drive. Our old Bounder had 5:13?s to get it moving and KEEP it moving. (Lower gears always pull better.) That put the peak torque right about 63 -64 mph which was perfect for me.
 

blw2

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I'll point out that finding the correct ratio has a lot to do with your transmission's ratios... Yours may be a lot different than mine....so a 4.1:1 on mine bay be the exact same result as a 3.7 on yours.
 

blw2

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In high school I had a friend who's dad owned the AAmco transmission shop in town.  He had a rather basic looking dodge that had I think something around a 4.x:1 rear end but also some heavy transmission mods.  That thing was lightning off the line, but his top speed was something like maybe 45-50 MPH with the engine screaming.

I've lost touch with that guy but I understand he went on to be a rather successful pro drag racer.
 

rbrdriver

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On my 2017 Ram 3500 it came with the Aisin tranny and 4.10 rears and I really like the pulling capabilities in the mountains. At 65 mph it turns around 1950 rpms which is all I would want to go anyways when towing. Just my 2 cents worth.......
 

gravesdiesel

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My 1996 Dodge Ram Diesel 5 speed has 4.10 gears and my 2003 Dodge Ram diesel 6 speed has 3.73 gears.  Both will pull anything I could ever hook to them.  I have a new Dodge Ram 4500 with the 6 speed Aisin automatic on order and the highest ratio axles I could get tin it are 4.10s.  You should definitely get a diesel.  It will pay for itself in fuel economy and resale value and you will enjoy pulling with it much better.  The Cummins in the Dodge Ram also has an exhaust brake which really helps on long descents.
 

Broke Boater

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In that link I posted, there's different sections to what was tested and compared. Search through it and look at the brake temps from going downhill. Rams brake temps are way lower from the engine brake managing the braking combined with using the brake peddle. It's common to read how guys see 100k miles on a set of brakes on their Rams. I use tow mode and engine brake every time I drive my truck, towing or not,,,gregg
 

2PawsRiver

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rbrdriver said:
On my 2017 Ram 3500 it came with the Aisin tranny and 4.10 rears and I really like the pulling capabilities in the mountains. At 65 mph it turns around 1950 rpms which is all I would want to go anyways when towing. Just my 2 cents worth.......

Just curious what your pulling and pin weight.  I just bought my 2018 Dodge 3500 dually and was talking to a gentleman selling a Momentum 399th.  He also pulled with a Dodge 3500 and had to put airbags in it as it sagged.  Not sure if it was an older model, but mine is supposed to be set to pull a 30,000 pound fifth wheel, I just can't imagine I would need to beef up the suspension.
 

rbrdriver

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2PawsRiver said:
Just curious what your pulling and pin weight.  I just bought my 2018 Dodge 3500 dually and was talking to a gentleman selling a Momentum 399th.  He also pulled with a Dodge 3500 and had to put airbags in it as it sagged.  Not sure if it was an older model, but mine is supposed to be set to pull a 30,000 pound fifth wheel, I just can't imagine I would need to beef up the suspension.

On mine it is set to pull a 30,000 trailer and is good for 5600 payload. Mine came with air-bags over leaf suspension and today we just pulled a 42' fiver (Keystone Alpine 3700FL) from the dealership to home and so far it did great. It was empty (dry-weight) then but we are now loading 'er up. Anyways no sagging yet...... 8)
 
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