Rear end ratios

[mt-ed]

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!

[BradW]

Yep, them some high gears right there. My mountain jeep has 5.13 gears, but 36" tires.

[specta]

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. 😄

I now have one more thing to be grateful for.

I'm grateful that my truck doesn't have 4.88 gears. LOL

[BradW]

Yeh, that's about 20% more rpms than my 4.10, so that would be about 4.88.

[specta]

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]

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]

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]

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]

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]

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]

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??

[Buzzcut1]

ticki2 wrote:

BradW wrote:

mbloof wrote:

BradW wrote:
All me knows is me loves the 4.10 gears in our 2018 PSD Superdutuy when hauling our camper and towing our jeep.

IMHO: not the best gears for fuel economy.

- Mark0.

I didn't buy the thing to cruise the mall or ride up and down the road doing 85 while towing nothing; I bought it to tow a load. I'm over 18k lbs 90% of the time and drive 65ish. I would be sick if I had gone with the 3.55 gears. I could have lived with 3.73 gears, but DA Ford no longer offers that ratio.

With what I haul/tow and how I drive, 3.55 gears would not have helped my mileage any.

brad

That's because you don't have the SUPER super duty that Kayteg has .

that and Brad is not a blowhard

[ticki2]

BradW wrote:

mbloof wrote:

BradW wrote:
All me knows is me loves the 4.10 gears in our 2018 PSD Superdutuy when hauling our camper and towing our jeep.

IMHO: not the best gears for fuel economy.

- Mark0.

I didn't buy the thing to cruise the mall or ride up and down the road doing 85 while towing nothing; I bought it to tow a load. I'm over 18k lbs 90% of the time and drive 65ish. I would be sick if I had gone with the 3.55 gears. I could have lived with 3.73 gears, but DA Ford no longer offers that ratio.

With what I haul/tow and how I drive, 3.55 gears would not have helped my mileage any.

brad

That's because you don't have the SUPER super duty that Kayteg has .

[Bedlam]

My GVW is close to 18k lbs when I have the trailer hanging off the rear and I am around 25K lbs GCW. I am very happy with my 4.44 gearing while at the 55-65 mph travel speeds in my area.

[Kayteg1]

When I was moving to different state, my combo was in the range of 18,000 lb as well. That was when I got pi** ed when I notice that my 3.55 differential allows the engine take 6% long grades without dropping from overdrive.
What's the purpose of automatic transmission, when you drive 300 miles on single gear?