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What gears do I need?

missouri_dave
Explorer
Explorer
Looking at a Ram 2500 to pull a 7K travel trailer. It will be a gasser with the 6.4 hemi. Should I get the 4.10 rear end or will the 3.73 do what I need?
45 REPLIES 45

garyp4951
Explorer III
Explorer III
I always liked math the best in school, and learned a lot from my Lego set with gears ๐Ÿ™‚

Dave_H_M
Explorer
Explorer
:S I thought about adding something that i thought would be productive, However this thing has gone too far South to ever recover. :B

BenK
Explorer
Explorer
Parker,

Like your comments, but see some response headers that don't show content
...Don't see comments from those on my blocked list...unless quoted like your quote below...

It is a constant because many do not under this technology, nor have the ability to understand the science & do the simple math well enough to make the correlation from that paper to the real world...free associative skills not high

Plus, get many, many PM's asking to comment...on this and many other topics. Normally only back to them via PM...unless there are more who are lurkers and don't post

Those video's and technical links mostly help...but...many won't go there and learn...or continue to not understand....


PS...this very topic has confused some of my past software engineers...nothing wrong...just the way of it...







parker.rowe wrote:
RCMAN46 wrote:
The 4.10 gearing will not give you more horsepower.

Gearing will not change the horsepower of a vehicle period.

Only modifications to the engine can increase horsepower.


Not sure why this keeps getting repeated.

We know gear ratios don't change what the engine puts out.

They multiply (or reduce in the case of overdrive gears) when get's sent to the tires to drive the truck forward.

If they didn't matter, all vehicles would have 1 speed transmissions and 1:1 rear end ratios.
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

Grit_dog
Nomad III
Nomad III
2Rad4U wrote:
4 pages on a pot that was answered in the first two replies. Then the pissing match started...

LOL


That's how the geezernet.net crew rolls!
I'm just trying to take lessons from here on how not to act once I become a member of AARP and forget to take my geritol every other day!
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5โ€ turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold

RCMAN46
Explorer
Explorer
parker.rowe wrote:
RCMAN46 wrote:
The 4.10 gearing will not give you more horsepower.

Gearing will not change the horsepower of a vehicle period.

Only modifications to the engine can increase horsepower.


Not sure why this keeps getting repeated.

We know gear ratios don't change what the engine puts out.

They multiply (or reduce in the case of overdrive gears) when get's sent to the tires to drive the truck forward.

If they didn't matter, all vehicles would have 1 speed transmissions and 1:1 rear end ratios.


Statements such as this is why what I stated keeps getting repeated.

"Now back to the above HP formula, there is now a change. The torque remains the same, but RPMs is now larger and multiplies torque. The constant stays the same (divisor is 5252). Nothing else changes, except for the increased (fractional) RPM...therefore, there is more HP.."

parker_rowe
Explorer
Explorer
2Rad4U wrote:
4 pages on a pot that was answered in the first two replies. Then the pissing match started...

LOL


Well, since the first 2 reply's were exactly the opposite of each other...I wouldn't call it answered that early. But yea, this happens in every gear ratio, half ton, and gas vs diesel thread.
2015 Starcraft TravelStar 239TBS 6500 GVWR
1997 GMC Suburban K2500 7.4 Vortec/4.10
1977 Kawasaki KZ1000

2Rad4U
Explorer II
Explorer II
4 pages on a pot that was answered in the first two replies. Then the pissing match started...

LOL
Chris
2005 Rockwood 2516G (sold)
2005 Max-Lite 24RS (sold)
2019 Rockwood 2608BS (sold)
2020 Grand Design 337RLS
2018 Chevy 2500HD

parker_rowe
Explorer
Explorer
RCMAN46 wrote:
The 4.10 gearing will not give you more horsepower.

Gearing will not change the horsepower of a vehicle period.

Only modifications to the engine can increase horsepower.


Not sure why this keeps getting repeated.

We know gear ratios don't change what the engine puts out.

They multiply (or reduce in the case of overdrive gears) when get's sent to the tires to drive the truck forward.

If they didn't matter, all vehicles would have 1 speed transmissions and 1:1 rear end ratios.
2015 Starcraft TravelStar 239TBS 6500 GVWR
1997 GMC Suburban K2500 7.4 Vortec/4.10
1977 Kawasaki KZ1000

BenK
Explorer
Explorer
Disagree...


First, the formula for determining HP is:

HP = torque x RPM / 5252



A higher numeric gear ratio will have more rev's from the input shaft (pinion gear) for each output shaft turn (ring gear)

The input shaft/pinion's torque is assumed to be the same in all cases for this discussion...in order to NOT get confused like the quote below where they think only increasing the ICE's torque/HP is it...

Since there are more rev's from the input shaft for each output shaft turn, the numbers of input shaft turns will impart more torque onto that output shaft's single turn

Fact.

Now back to the above HP formula, there is now a change. The torque remains the same, but RPMs is now larger and multiplies torque. The constant stays the same (divisor is 5252). Nothing else changes, except for the increased (fractional) RPM...therefore, there is more HP...

Wikipedia Gear train (there are tons more sites)


What is torque and How does gear ratio affect Torque?


YouTube, Gear transfer torque



This one shows the tranny gears and hope it gets it across...ask why you can't get it going in highest gear...even though it is the same ICE?
YouTube,Car Gear Ratios (Calculate Wheel RPMs, Torque at Wheels, and Force at Wheels)




RCMAN46 wrote:
The 4.10 gearing will not give you more horsepower.

Gearing will not change the horsepower of a vehicle period.

Only modifications to the engine can increase horsepower.
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

parker_rowe
Explorer
Explorer
ib516 wrote:
Beentherefixedthat wrote:

Further the 4:10 will make what is not great gas mileage much worse.

This is NOT the case.

Here is a quote from a GM powertrain engineer:

"How much of a difference does the choice of axle make? A 2013 Sierra 2500HD with a 6.0L V-8 and four-wheel drive can tow a maximum of 9,900 pounds with a 3.73:1 ratio or 14,400 pounds with a 4.10:1 ratio. Martuch estimates the fuel economy difference at highway speeds would be around 0.2-0.3 mpg between those two ratios, though reduced engine noise is also a benefit of maintaining lower engine speeds with the more-efficient ratio.
LINK

"According to Roger Clark, senior manager of GM's Energy Integration and Fuel Economy Learning Vehicles Program, which handles fuel-economy development of all GM trucks and SUVs, fuel economy may not change much by going to an optional axle ratio. "The typical combined-fuel-economy impact, based on lab test conditions, is a difference of about 0.4 mpg to 0.6 mpg between the standard gear ratio (3.42 or 3.55) and the lowest (4.10) offered. That change is linear, too. Choosing 3.73 or 3.92 gear ratios would have even less of an effect on fuel economy." Clark says that in the real world, choosing a lower gear ratio may not even show up in fuel economy associated with city driving. It's the steady-state, long-distance freeway romps where lower axle ratios have the most effect."

It's about 0.5 mpg or so between a 3.42/3.55 and a 3.92/4.10. Not much.


Yep. Obviously my truck is completely different than a new Ram. But I picked up .5-1mpg towing the camper, and lost about the same unloaded.

Going from 3.73's to 4.56's. The difference in towing was huge.

Any new truck I buy will be used for truck stuff, no commuting. So I would always opt for the numerically higher gear ratio if offered. People say to tack on the 10K diesel option just to give you the buffer in capability.
Why do they freak out about doing the same with the $500 option gear ratio to increase tow rating?
2015 Starcraft TravelStar 239TBS 6500 GVWR
1997 GMC Suburban K2500 7.4 Vortec/4.10
1977 Kawasaki KZ1000

larry_barnhart
Explorer
Explorer
Our 1st rv was a TT. We had a chev van that was very plush with tv etc so that was the tow vehicle 3.42 rear that was not good so changed to 4.10. The tow was much nicer and didn't have to have the pedal to the floor. Maybe the new trucks are different but I agree with ib516.

chevman
chevman
2019 rockwood 34 ft fifth wheel sold
2005 3500 2wd duramax CC dually
prodigy



KSH 55 inbed fuel tank

scanguage II
TD-EOC
Induction Overhaul Kit
TST tire monitors
FMCA # F479110

ib516
Explorer
Explorer
Beentherefixedthat wrote:

Further the 4:10 will make what is not great gas mileage much worse.

This is NOT the case.

Here is a quote from a GM powertrain engineer:

"How much of a difference does the choice of axle make? A 2013 Sierra 2500HD with a 6.0L V-8 and four-wheel drive can tow a maximum of 9,900 pounds with a 3.73:1 ratio or 14,400 pounds with a 4.10:1 ratio. Martuch estimates the fuel economy difference at highway speeds would be around 0.2-0.3 mpg between those two ratios, though reduced engine noise is also a benefit of maintaining lower engine speeds with the more-efficient ratio.
LINK

"According to Roger Clark, senior manager of GM's Energy Integration and Fuel Economy Learning Vehicles Program, which handles fuel-economy development of all GM trucks and SUVs, fuel economy may not change much by going to an optional axle ratio. "The typical combined-fuel-economy impact, based on lab test conditions, is a difference of about 0.4 mpg to 0.6 mpg between the standard gear ratio (3.42 or 3.55) and the lowest (4.10) offered. That change is linear, too. Choosing 3.73 or 3.92 gear ratios would have even less of an effect on fuel economy." Clark says that in the real world, choosing a lower gear ratio may not even show up in fuel economy associated with city driving. It's the steady-state, long-distance freeway romps where lower axle ratios have the most effect."

It's about 0.5 mpg or so between a 3.42/3.55 and a 3.92/4.10. Not much.
Prev: 2010 Cougar 322QBS (junk)
02 Dodge 2500 4x4 5.9L CTD 3.55
07 Dodge 3500 4x4 SRW Mega 5.9L CTD 3.73
14 Ram 2500 4x4 Crew 6.4L Hemi 4.10
06 Chevy 1500 4x4 E-Cab 3.73 5.3L
07 Dodge 1500 5.7L Hemi 3.55 / 2010 Jayco 17z
All above are sold, no longer own an RV

ib516
Explorer
Explorer
RCMAN46 wrote:
The 4.10 gearing will not give you more horsepower.

Gearing will not change the horsepower of a vehicle period.

Only modifications to the engine can increase horsepower.

You are correct, but the 4.10s do offer more torque at the wheels than the 3.73s do. That will help get heavy loads moving. There is a reason the manufacturer increases the tow rating and GCWR by 3000# when you opt for the 4.10s.
Prev: 2010 Cougar 322QBS (junk)
02 Dodge 2500 4x4 5.9L CTD 3.55
07 Dodge 3500 4x4 SRW Mega 5.9L CTD 3.73
14 Ram 2500 4x4 Crew 6.4L Hemi 4.10
06 Chevy 1500 4x4 E-Cab 3.73 5.3L
07 Dodge 1500 5.7L Hemi 3.55 / 2010 Jayco 17z
All above are sold, no longer own an RV

RCMAN46
Explorer
Explorer
The 4.10 gearing will not give you more horsepower.

Gearing will not change the horsepower of a vehicle period.

Only modifications to the engine can increase horsepower.