I've read where some truck campers specify the ratio of gearing in the differential of their trucks used for truck camping. Would anyone out there be so kind so as to explain to me what the advantages/disadvantages are to these different configurations?Thanks in advance!

The higher the gear ratio numerically (3.55, 3.73, 4.10, 4.30, 4.44, 4.56) the more revolutions your driveshaft has to turn to make the tires go 1 Revolution. This increase in gear numerical gear ratio decrease effort required to turn the tires thus making it easier for a vehicle accelerate and pull a load. If you have a light vehicle that does not pull heavy loads you can use a numerically lower gear like 3.08 which decreases the rpm of an engine at speed and thereby increase fuel economy. On the other hand, if you have a heavy vehicle that frequently pulls heavy loads you’d want a higher numeric gear ratio to make it easier to accelerate and pull heavy loads.

Generally the modern 6 to 10 speed transmissions have made changing rear gears obsolete.Now if you have an old 3 or 4 speed and you feel like you are often in the wrong gear then consider a change.

time2roll wrote:Generally the modern 6 to 10 speed transmissions have made changing rear gears obsolete.Now if you have an old 3 or 4 speed and you feel like you are often in the wrong gear then consider a change.With 10 speeds perhaps but at least some 6 speeds aren’t that different than older 4 speeds when it comes to towing heavy. Our 6 speed Yukon will top 60 in 2nd gear so it would definitely need lower gears in the rear if I wanted to tow anything substantial with it. The 2 added gears allow for lower RPM when cruising in the 40-70mph range for better mileage.

Final gear ratio is always a balance between engine torque and differential gearing. For years I drive European vehicles, who I love for high differential ratio as they take most of the grades without downshifting. My family members on other hand drive Toyotas, who I get to drive occasionally. It gets really annoying when Toyota needs to downshift with each wind gust or freeway overpass. But then Toyotas get better mpg.Same with trucks, but here, on this forum you will find "conservative" members who drove trucks with high differential ratios for decades and can't comprehend changes combustion engines made in last years. Most of the members will advise you to get high differential ratio for camper. I educated myself and for my 440 HP dually - have chosen the lowest differential ratio Ford would install, yet still the truck takes all those 15-17 miles grades we have with 6000 lb camper never dropping from overdrive at 1600 rpm. Frankly I wish I could get even lower than 3.55 differential ratio for fuel economy. It doesn't make sense to gear truck for hauling 20,000lb rigs without downshifting.Transmissions have gears for a reason.

X2, Kayteg. My new Silverado with the eight speed transmission and 3.24 rear end pulls better than my 2015 Tahoe with the six speed and 3.42.

Rear end ratios | Good Sam Community

BradW
Explorer II
Dec 27, 2019
Yep, them some high gears right there. My mountain jeep has 5.13 gears, but 36" tires.
specta
Explorer
Dec 27, 2019
BradW wrote:
Yeh, that's about 20% more rpms than my 4.10, so that would be about 4.88.

Thanks, you saved me from climbing under the truck. :D

I now have one more thing to be grateful for.

I'm grateful that my truck doesn't have 4.88 gears. LOL
BradW
Explorer II
Dec 27, 2019
Yeh, that's about 20% more rpms than my 4.10, so that would be about 4.88.
specta
Explorer
Dec 27, 2019
Bedlam wrote:
If you can read the axle code, 4L was the limited slip 4.30's and 8L was the 4.88 with limited slip. It appears that there was a high capacity tow option allowing you to get the 4.88 ratios and tow an additional 2 tons.

I'll climb under there later today and see what I can see.

I do know that it is a limited slip and from others it sounds like it has 4.88 gears.

The truck with only 160,000 miles is on its third engine. I believe the person who was the primary driver for years thought it was OK to travel at 80 mph.

I've read that redline on these 6.4s is 3700 rpm and anything over that starts floating valves and doing other valvetrain damage.

I'm not normally a 65 mph driver but the truck seems to be fairly comfortable there, even towing the snowcat.

I like the interior ergonomics better in this one than our 2017 F-250. Just seems more comfortable to me other than the ride. LOL
specta
Explorer
Dec 27, 2019
Bedlam wrote:
The F450 pickups used to come with 4.30 ratios and no other choice. I'm not sure if that is still the case on new models.

Its a 2009 F-450 stake bed.
Bedlam
Moderator
Dec 27, 2019
If you can read the axle code, 4L was the limited slip 4.30's and 8L was the 4.88 with limited slip. It appears that there was a high capacity tow option allowing you to get the 4.88 ratios and tow an additional 2 tons.
Kayteg1
Explorer II
Dec 27, 2019
2400 rpm that's what I had on my 1999 PSD with 10' flatbed.
Customers could hear me coming 4 blocks away.
Ah sweat 7.3 memories.
jimh406
Explorer III
Dec 27, 2019
specta wrote:
I took my work truck in today to get serviced. Just an oil change, some misc services and to get the tires rotated.

Its a 2009 F-450 4wd 6.4L diesel with 225/70R/19.5 tires.

At 65 mph its turning about 2400 RPM.

What gears would you guess it has??

That's more than mine at 4.30 turns, so my guess is 4.88.
Bedlam
Moderator
Dec 27, 2019
The F450 pickups used to come with 4.30 ratios and no other choice. I'm not sure if that is still the case on new models.
specta
Explorer
Dec 27, 2019
I took my work truck in today to get serviced. Just an oil change, some misc services and to get the tires rotated.

Its a 2009 F-450 4wd 6.4L diesel with 225/70R/19.5 tires.

At 65 mph its turning about 2400 RPM.

What gears would you guess it has??