Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
RV Trip Planning Discussions

Go Back   iRV2 Forums > TRAVEL TRAILER, 5th WHEEL & TRUCK CAMPER FORUMS > Trailer Towing and Tow Vehicles Discussion
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 01-28-2017, 08:42 AM   #1
Member
 
Join Date: Dec 2016
Posts: 85
Blog Entries: 3
Rear Axle Gear Ratios - Best for Towing

Getting confused about rear axle gear ratios and what is the best for full-time towing a trailer or fifth wheel. 4.10? 3.73?

So, what do you think?
CascadeBob is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 01-28-2017, 08:45 AM   #2
Senior Member
 
Join Date: Oct 2016
Posts: 351
Quote:
Originally Posted by CascadeBob View Post
Getting confused about rear axle gear ratios and what is the best for full-time towing a trailer or fifth wheel. 4.10? 3.73?

So, what do you think?
I am no expert but I pull a 16.5k, 38fter with a 6.7 Ford with 3.55 gears just fine.
Fishalaska1 is offline   Reply With Quote
Old 01-28-2017, 10:13 AM   #3
Senior Member
 
Join Date: Oct 2015
Posts: 362
Not apples to apples, but my observations.

My truck is stock 2013 Cummins 3.42 with 13,500 GVWR bumper pull TH.

My fathers is tuned, deleted, 4.10 DRW with 17k 5th wheel TH.

On the longer and steeper grades letting the transmission in T/H do the shifting and cruise set as I would start to bog down on he would gain on me until my truck downshifted into 5th then I'd start to pull away until his shifted and by the top of the hill our spacing was the same as when we started.

I locked out 6th, and he would be playing catch up.

With these 6 speed trans with double overdrive and massive power from the current diesel offerings the gear ratio isn't as important as in a naturally aspirated gas rig, in which case go as numerically high as you can for best towing performance.
drittal is offline   Reply With Quote
Old 01-28-2017, 10:30 AM   #4
Senior Member
 
JohnBoyToo's Avatar
 
Monaco Owners Club
Join Date: May 2012
Location: DFW, Tex-US
Posts: 6,196
I think:
Don't overthink it
But towing with what engine and what load ?!?
anything can tow 5k lbs...

just buy the truck you want that will do the job and
don't expend the money to change what the engineers designed it for

our 2012 and 2013 6.7 fords with 3.55's towed heavy, HEAVY 5'ers without a whimper...

But, my truck's were not just full time pullers so that's why the 3.55's worked for me... if yours is never unhooked from 16k+ lbs, then consider shorter gears, but not a show stopper either way.
__________________
'11 Monaco Diplomat 43DFT RR10R pushed by a '14 Jeep Wrangler JKU. History.. 5'ers: 13 Redwood 38gk(junk!), 11 MVP Destiny, Open Range TT, Winn LeSharo, C's, popups, vans, tents...
JohnBoyToo is offline   Reply With Quote
Old 01-28-2017, 11:34 AM   #5
Member
 
Join Date: Aug 2011
Location: Florida
Posts: 44
Rear Axle Gear Ratios - Best for Towing

It largely depends on the truck and the load you plan to pull with it. If you're talking a new diesel with a 6+ speed transmission, then a 3.55 or 3.73 gear truck may be fine, but a gasser with an 8 speed may only need a 3.42, or a 3.73 with a 6 speed. Basically nearly all trucks have different tow capacities depending on what gear and transmission they come equipped with.

Figure out the weight of your trailer and your expected payload, then look at the charts for tow capacities and payloads then pick the truck configuration that is more than what you need, but not way over, unless you're at the top of course. It's always better to have more truck than you need. Though breaking even is possible, it's generally safer to have more truck than trailer.

If you just want a generic answer. Then the truck with the biggest engine, the most transmission gears, and the higher numerical gear ratio is generally going to be the best tow vehicle.
MagnaPilot is offline   Reply With Quote
Old 01-28-2017, 03:34 PM   #6
Senior Member
 
Join Date: Aug 2012
Posts: 1,580
A diesel engine operates at a much lower RPM than a gas engine, when discussing gear ratios you don't compare diesel and gas.

Since modern transmissions have overdrive in the top gears, you multiply the top gear times the axle gear to get the real result.

Tire diameter is another big factor that needs to be considered.

Just throwing out your favorite numbers is not useful.
lynnmor is offline   Reply With Quote
Old 01-28-2017, 04:44 PM   #7
Senior Member
 
Join Date: Aug 2015
Location: Phoenix, Oregon
Posts: 2,207
Do a search for a rpm-mph calculator. Here is a link to one Engine RPM Calculator There are many of them. Play with numbers until you find a gearing combination that works for you. I have always looked for something that would provide a desired top speed somewhere near the peak torque rpm of the engine.

Best of luck.

Steve
dix39 is offline   Reply With Quote
Old 01-28-2017, 05:22 PM   #8
Junior Member
 
Join Date: Jan 2017
Location: Salfordville
Posts: 16
It depends on the torque curve of the engine and how the transmission and torque converter are set up. Today's trucks are different. I owned a 2011 F350 6.7 power stroke with 3.55's. I pulled 11k travel trailer- on level ground it pulled veery well. The power stroke has loads of torque down low around 1400 rpms. I was able to keep the trans in 6th (high) as long as I kept going at 70mph cruising. If I hit slightest grade it would go down to 5th. The downside was if I got into traffic or stuck behind slower vehicle and dropped below 65, the trans would be shifting up, down. The 3.55's just weren't good for me towing 11k without the trans doing a lot of shifting. I just got a 2016 F350 dully with power stroke 3.73's, now this is the perfect set up. I can run down to 60mph then back to crushing 65-70 without annoying shifting.
engineer78 is offline   Reply With Quote
Old 01-28-2017, 06:55 PM   #9
Senior Member
 
Join Date: Oct 2015
Posts: 362
Quote:
Originally Posted by engineer78 View Post
It depends on the torque curve of the engine and how the transmission and torque converter are set up. Today's trucks are different. I owned a 2011 F350 6.7 power stroke with 3.55's. I pulled 11k travel trailer- on level ground it pulled veery well. The power stroke has loads of torque down low around 1400 rpms. I was able to keep the trans in 6th (high) as long as I kept going at 70mph cruising. If I hit slightest grade it would go down to 5th. The downside was if I got into traffic or stuck behind slower vehicle and dropped below 65, the trans would be shifting up, down. The 3.55's just weren't good for me towing 11k without the trans doing a lot of shifting. I just got a 2016 F350 dully with power stroke 3.73's, now this is the perfect set up. I can run down to 60mph then back to crushing 65-70 without annoying shifting.


Lock out 6th, problem solved and probably get a little better mpg too.
drittal is offline   Reply With Quote
Old 01-28-2017, 07:06 PM   #10
Senior Member
 
Join Date: Dec 2012
Location: Oregon
Posts: 6,596
I have 3.73's and a CTD. Under 60mph I leave it in 5th. If I run up to 65mph then I'll shift it to 6th. I find 6th at 50-60mph wants to shift down often enough that I just stic it in 5th. Last trip we took I left it in 5th probably 70% of the time and noticed no change in mpg. I've got 32" tires and my CTD turns 1800-2000rpm running 50-60mph in 5th. Perfect rpm for hilly and mountainous roads. I'm also towing light at around only 9000lbs.
Cumminsfan is offline   Reply With Quote
Old 01-29-2017, 07:22 AM   #11
Member
 
Join Date: Dec 2016
Posts: 85
Blog Entries: 3
Whew! Yep - complicated. I did purposely post a g3eneric question to avoid the conversation focusing on truck brands or other distractions, but - since many of you ask:


We haven't bought our set up yet, but we're pretty sure we'll set ourselves up in the following:


Towing vehicle: Used Silverado 3500 or maybe Ford 350, 6.6 or 6.4 diesel, crew cab, 6-speed tranny, 4X4, standard (6') bed, between 2008 - 2015 vintage truck.


Fifth Wheel: Northwood Fox Mountain 235RLS, gross vehicle wt (loaded) 11,500 lbs, hitch wt (dry) 1,375 lbs.


A one-ton truck is probably way more than we need for that fifth wheel, but we may trade up fivers in the future and want to stay far below truck towing capacities since we plan to boondock a lot (up those steep, wash-board BLM and Forest Service roads).


Still confused about the actual axle ratios. Is it the smaller the gear-ratio number the more revolutions for the engine? So is a 3.73 rear end geared "lower" to haul more weight, all other things being equal?


And is the downside to lower gears that they spin faster at higher speeds (producing a higher risk of heating up and burning out)?
CascadeBob is offline   Reply With Quote
Old 01-29-2017, 07:36 AM   #12
Senior Member
 
Join Date: Aug 2012
Posts: 1,580
Quote:
Originally Posted by CascadeBob View Post

Still confused about the actual axle ratios. Is it the smaller the gear-ratio number the more revolutions for the engine? So is a 3.73 rear end geared "lower" to haul more weight, all other things being equal?


And is the downside to lower gears that they spin faster at higher speeds (producing a higher risk of heating up and burning out)?

You are correct on the axle ratio question.

Lower gears will allow the engine to spin faster at all times. You are incorrect on the "heating up" question, the opposite is true. The lower gears are better for the transmission as well.

Skip the 6.4, and go to a 6.7 built after March 2011, if you decide on a Ford.
lynnmor is offline   Reply With Quote
Old 01-29-2017, 08:07 AM   #13
Senior Member
 
Join Date: Feb 2009
Location: Ca
Posts: 1,076
Why a 6' bed on a 3500? Just curious.....My 3500 6.7 CTD has 3.73 gears.
timetogo is offline   Reply With Quote
Old 01-29-2017, 08:08 AM   #14
Senior Member
 
Join Date: Oct 2015
Posts: 362
Quote:
Originally Posted by CascadeBob View Post
...or 6.4 diesel...
NO. STAY AWAY From 6.4.

Quote:
Still confused about the actual axle ratios. Is it the smaller the gear-ratio number the more revolutions for the engine? So is a 3.73 rear end geared "lower" to haul more weight, all other things being equal?

And is the downside to lower gears that they spin faster at higher speeds (producing a higher risk of heating up and burning out)?

The higher the numeric number, the lower it is geared. 4.10:1 is lower geared than 3.73:1. 4.10 will tow more with less effort.

The only downside to worry about is more engine revs and burning more fuel at the same speeds.

With the smaller fifth wheel you are looking at a higher geared rig will have no problem towing it.
drittal is offline   Reply With Quote
Reply

Tags
tow, towing



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
A class to C class rear axle ratios opnroad Class A Motorhome Discussions 9 02-28-2015 09:20 AM
Gear ratios jim81147 Trailer Towing and Tow Vehicles Discussion 8 08-27-2014 09:18 AM
Gear Ratios rababk Class A Motorhome Discussions 5 07-18-2013 10:42 AM
Power to weight ratios and torque to weight ratios Mystery Newmar Owner's Forum 8 01-03-2013 05:16 AM
axle ratios Clay Trailer Towing and Tow Vehicles Discussion 13 05-25-2009 10:18 AM

» Featured Campgrounds

Reviews provided by


All times are GMT -6. The time now is 03:38 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.