Rear Axle Gear

[YankeeBP]

Am looking for opinion/advice on choosing an adequate rear axle gear ratio. Will be pulling a Cruiser RV Fun Finder 214 (approaximately 5000 lbs. loaded) with a Ford F-150 Ecoboost (yet to be purchased). My thought is a 3:55 rear axle gear. What are your thoughts? Will be towing in the mountain states and Alaska.

[YankeeBP]

Thanks, everyone, for your replies. Got lots of info to mull over now.

[facory]

roadtoadflorida wrote:
I just switched out my 3:23 rear end to a 4:10 ring and pinion. What a difference in my '06 SIlverado 1500 Crew Cab, 4.8. I now can tow my 25" Dutchmen Lite much more easier. $900 for all labor, gears, bearings, seals, etc. Cheaper than a new truck. Just wanted to share.

Typical example of how the rear end ratio affects torque at the rear wheel. 4X4 TVs would need to change both front and rear axle ratios. It's what happens at the rear wheels not just what happens at the engine.

[APT]

facory wrote:
Rear axle ratio is very important.

With older 3-4 speed, yes. Not with today's 6-spd transmissions. Today's 6-spd with 3.08 is the prior generation 4-spd with 4.10 axle. Actually, it's still better offering more narrow gear spacing. Look at Column E for the wheel torque multiplier.



Here's the F-150:



3.73 is "better" for pulling, but the reason to get it in the F-150 is because it is packaged with both of the two packaged that increase payload/GVWR which is the most common overloaded rating for RVers.

[facory]

Rear axle ratio is very important. It directly affects torque, and that's what gets you down the road and up the next hill. My Ford F150 with the 5.4 and tow package has the 3.73 rear end. It works very well. Anything higher than that (lower number) is going to make the tranny downshift for often to compensate for the rear end ratio. I would not go below a 3.55, but would opt for the 3.73 or even 4.10 if you will be towing a heavy trailer and doing a lot of hills.

[mbopp]

My $.02:

The TT in my sig probably weighs in at 5500-5700# loaded. My EB F150 has the Standard tow package and 3.55 gears. The most I've climbed was a few 6% grades but it did just fine.
I have to park in a municipal garage and didn't want the big tow mirrors. CIPA slip-ons do the duty when I'm towing.

[roadtoadflorida]

I just switched out my 3:23 rear end to a 4:10 ring and pinion. What a difference in my '06 SIlverado 1500 Crew Cab, 4.8. I now can tow my 25" Dutchmen Lite much more easier. $900 for all labor, gears, bearings, seals, etc. Cheaper than a new truck. Just wanted to share.

[Tystevens]

I have 3.55 and 'regular' tow package in my F150. My trailer is 6000-6500 lbs loaded. The truck handles it with ease. We can cruise along at 65 mph in 6th gear, cruise on, and only downshifts when going up a hill.

I think the biggest reason to get max tow would be the nice extendable towing mirrors. That would be worth it to me.

[APT]

Rated, yes Terrry. But practically and butt dyno perception axle ratio is not as important when it comes to RVing.

[Terryallan]

APT wrote:
In the 15 years I have followed the halt ton market, any given person seems to get the same unloaded fuel economy between the shortest and tallest gear ratios. Their driving style affects it compared to others. The 6+ gear transmissions have taken the axle ratio out of the acceleration/performance equation, but but I still say 3.73. No reason not to. I also recommend the max trailer towing package for the extra payload which means forces the 3.73 gear anyway.

The 6 peed has not taken the rear gear completely out. As the 3.73 is rated to tow MUCH more than the 3.15

[johndeerefarmer]

I have had two ecoboosts and I recommend the max tow package. You get the 3.73 rear end, larger tow mirrors and better cooling. You also get an extra 400 lbs of payload with the max tow.
The main thing that kills fuel economy is larger, heavier tires and a heavier truck. My '11 Super Cab was over 1000 lbs lighter than my '13 fully loaded King Ranch and fuel economy was 2-3 mpg less with it.

[APT]

In the 15 years I have followed the halt ton market, any given person seems to get the same unloaded fuel economy between the shortest and tallest gear ratios. Their driving style affects it compared to others. The 6+ gear transmissions have taken the axle ratio out of the acceleration/performance equation, but but I still say 3.73. No reason not to. I also recommend the max trailer towing package for the extra payload which means forces the 3.73 gear anyway.

[MitchF150]

I have been told that the lower geared, bigger tired F-150 really suffers on gas mileage around town and towing.

I commute daily 18 miles each way and usually add 6-12 miles a day if I go out to lunch or have a client appointment and avg 17 mpg between gas stops. I've got the 3.73's and 20" wheels.. I'm mostly in rush hour traffic and avg maybe 30 mph over a 2 week period.

I just did a 210 mile straight hwy run to Sequim from Puyallup WA and back where my folks live and got a solid 22 mpg on the computer.. Yes, I know everyone says the computer is always wrong, but mine is pretty darn close and I'm rounding DOWN anyway... 😉

A lot will depend on how your drive it too of course.. Keep in those turbos and it'll suck the gas! I do get into those turbos a bit too, but I can also drive like Grandpa too... 🙂

I think I get better mpg with the 3.73's on my commute because of how slow my avg mph end up being.. Anyway, it's all speculative and get what you feel will work best for you and go from there... Folks are happy with 3.15 geared trucks, so there you go! 🙂

Mitch

[rbpru]

I tow a 26 ft. TT with an F-150 EcoBoost and 3.55 gear with no problems using the tow haul feature.

I have been told that the lower geared, bigger tired F-150 really suffers on gas mileage around town and towing.

I get 19 to 20 mpg with no TT on the flat at 65 mph and 10 mph on the flat towing the TT at 60 mph.

Since I use my truck every day, non-towing mileage in important.

[MitchF150]

I got lucky and found my brand new Max Tow F150 sitting in the back lot with the USED trucks and got it for $10k under sticker... 🙂



I like the 3.73's with the factory 20" wheels.. It runs in 6th gear most of the time on the hwy towing my #5000 TT. Not towing, it gets me anywhere between 21 and 23 mpg going 60-65 mph. Going 70 mph, it's running around 1800 rpms.

I've not taken it on a road trip where the speed limit is 70 while not towing, so not sure how it'll do at that speed? Towing I get around 10-11 mpg.

The pull the Eco has with the 3.73's is really strong.. I love it! 🙂

Good luck with the search!

Mitch