rear end ratio

I had the exact same concern, see my post below. I decided to keep what I have and spend the money on something else.

Click here for my post and feedbacks from other members.

Thanks will do, hope you are dry, its been a bit wet in your area. but at least some of the reservoirs will get a chance to fill up some. lake Travis was a bit low well extremely low last time I had seen it.

Changing gears will not reduce the rpms needed to climb a hill. If you need 3000 rpms with your current gears, you will still need 3000 rpms with your 4:56 gears, just maybe in one higher gear.

Are your tires oversized?

g4sbrg wrote:
OK so I feel I am stressing the truck to much in hilly conditions pulling my 5th wheel camper, seems fine out on open road but needs help near the lakes and camp grounds going up those sometimes large hills, currently planning on changing from the 373 rear end to a 456 one would think I would loose a lot of mpg but in reality in general wont I be lowering the needed rpm and reducing the extreme rpm needed to go upwards, thus it will be a wash while towing, and at this point is it not more about performance towing. the truck is a tow truck for me not transportation to and from work or every day driving.
2000 f150, 5.4L 373 rear end

your comments would be appreciated

How heavy is the 5er? It may just be too much for your truck.

I had 3.55 in my 2001 and it always seemed to be between gears. Much better with 4.10 as now I mostly set the cruise and glide on down the highway. I wanted 4.30 but not available front and rear so I debated on 4.10 vs. 4.56 for a time. I chose 4.10 and have been happy. There are some times 4.56 would be preferred.

If you are already at 3.73 You should be looking at 4.56 or 4.88
You will still slow on the hills but the drivability will improve.

Usually settle in about 3500 rpm and hold the gear to the top of the hill.
I even set my cruise control by RPM.

My 2000 E450 based RV has a Rear axle ratio 4.63:1 from Ford.

Lower Gears will help pull the load from a start and up hills.
They will also help with braking going down.

The only thing a lower gear Rear axle ratio 4.63:1 vs 3:73 will be top speed. That is because you will build RPMs to sooner. You will have a higher RPM at 60 MPH with the 4.63:1 gear than you had with the 3:73, however there will not be a dramatic difference. The lower top speed should not be a problem in your use.

You will find towing easier with the 4.63:1 gears and not strain
the motor to move your load and the sweet spot for best MPG will be
slightly slower.

The heaver the load, the lower gears you need.
Rear axle ratio 4.63:1 is a lower gear then 3:73.

Feel your pain, see my sig. Saving money for a newer truck, one that has a bit more HP, better gearing and more transmission speeds.

Our vintage of trucks are much different than todays.

Suggest the OP save money for the next truck and drive with OD locked out for now. Biggest problem with Ford 4 sp truck transmissions IMO is that when more torque is needed while driving in OD the torque converter unlocks first; then if that is not enough, it downshifts to 3rd. While the converter is unlocked much heat is generated, the enemy of transmissions. Changing to a numerically higher ratio might just run this way more often instead of shifting down to 3rd. Also, likely the OP has a 4R100 transmission which is not famous for going over 100K mi. My son has a 2003 F-150 5.4 4R100—his went out at 100K and he immediately found 3 friends with the same story. Torque peak for the 2V 5.4 is 2500 RPM so running in 3rd (OD locked out) at close to this RPM would give lots of torque and best engine efficiency. Fuel consumption is largely a factor of how much work is being done and engine efficiency. Towing down the road at the same speed is going to use a very similar amount of fuel regardless to the gear. I checked fuel economy towing with our 5.4 Expedition with and without OD locked out—no statistical difference. OP, when you go looking to trade to a newer truck try to get one with 6 or more speeds in the transmission—the closer gears are just wonderful for towing.

I had the same issue with my 2006 F-150 5.4 3.73. I even went as far as rebuilding the transmission with a heavy duty clutch pack, shift kit and drilled out valve body specifically set up for towing, cat back exhaust, cold air intake, premium fuel and a Edge Evolution programmer set in tow mode and it was still a dog. The problem is there is too much spacing between the gears in the transmission and only 4 gears.

My remedy was a new 2014 Ecoboost and with only a 3.55 rear end. Between the 420 Lb Ft torque of the Ecoboost and the 6 speed transmission with Tow/Haul mode it is night and day different towing the same trailer to the same locations. Where the 5.4 would crawl up a grade screaming like a banshee at 35 MPH the Ecoboost goes up it at 55-60 MPH in 4th gear at only 3500 RPM and doesn't need to downshift further. The problem is the gears in the transmission are spaced to wide and there are not enough of them, not the rear end gearing. The spacing is such that it either lugs or screams and is out of the torque range either way which is not optimal.

Technology has come a long long way in a few short years and I would never have believed it if I didn't drive it for myself. 218 cubic inches but 365HP and 420 lb ft of torque at a low 2500 RPM, it never breaks a sweat.