A few months ago I bought an '05 F-150 XL from a man going through a divorce. I was looking for a second truck for my lawn care business and this was a great deal. I use it 95% of the time towing a 14' single axle landscape trailer weighing approximately 3,000 lbs loaded.

The truck is a 4.6L, automatic, super-cab, short bed with the trailer tow package and has about 16,000 miles. The rear end is a regular (no limited slip) one with the 3.55 axle. I believe this is where my only real complaint lies.

It's gotten to where I just don't even turn the overdrive on unless I'm running 65mph or more on the interstate. I know there will be 100 opinions on OD towing but a 200 plus hp truck still shouldn't hunt through gears like this one does when only pulling 3,000 lbs! I'm not just talking higway speeds but you can tell the trailer is just more than the truck wants back there anywhere I go.

I believe the 3.55 axle is my problem. If so, my big questions are:
1. How big a deal is it to change out a rear end?
2. Can I go limited slip now?
3. Should I go 3.73 or maybe even 4.10 or something like that? I obviously want better tow performance but I don't want it screaming rpm's on the highway either.
4. Are there computer changes that would need to be made as well?
5. And of course, about what would I expect this to do to my wallet? I absolutely have zero time to even try this myself with running the landscape business.

Thanks in advance for any tips. I guess the biggest thing I'm trying to decide is whether this is even feasible or not.

 

switch to 3.73 gears and the limited slip or a locker

the swap is fairly straightforward. a good shop should only take 3-4 hours at most to install a set. parts will cost you about $600 for quality stuff.

I'd also recommend a cold air intake and a tuner. they'll liven up the motor and make your tow experience more enjoyable

 

4.10 our trucks are geared extremely low it seems, im running at 4.56 gearing on my 4.6 with a 32 tall inch tire, ive ran it with stock tires and yes there is a HUGE difference, but the rpms are nothing extreme, and infact i gained so much city mpg, that the loss i gained highway balances out.

id say 4.10, just because 3.75 would give u a little more umph, but for actual power and to get your monies worth, id say 4.10.

You will need to reprogram your computer for the gears, the dealership can do this.

 

Even with the new gears the truck will continue to hunt in and out of overdrive if you use it. My 5.4 does it with the 3.73 gears, and on long grades towing it still needs to shift down to 2nd. Mine gets annoying with a 1200 pound (empty) trailer. I just lock it out of overdrive as soon as I hook the trailer up. As to the gear swap, good mechanic should be able to do it fairly easliy, but find one that KNOWS how to set rears up GOOD, or it won't last. As to the gears, they aren't all that expensive, but the limited slip will probably cost more than the gearset, it's a good thing do do since your already in there, but does add some more money to the job. The underlying issue here is the truck is heavy, mine weighed in at 5975 empty, and your can take off another 500 for not having 4wd, but thats still 5475, and thats still a heavy truck.

 

Well, I think thus far it has been assumed you own a 2 wheel drive truck. Is this the case?

 

You know, if I tow at highway speeds without OD, the 3.55 might be the better choice. 3rd gear doing 70 mph would really keep it wound up with 3.73's or higher. Maybe I just really need to forget OD when towing. Now my concern if I go that route is the rpm's. I have no tach on this truck. Any idea how many rpm's it's turning at around 65-70 mph in third?

By the way, WheelMA1; it is 2WD. Thanks guys

 

When I tow with the OD locked out at 70 it's in the 2500-3000 neighborhood, don't remember exactly. Yes, the 3.55 would keep lower RPM on the highway in 3rd, but it's going to downshift to second sooner when you hit a grade, beacuse of the higher gear ratio. My 5 speed escort ZX2 runs at about 3500@ 70 in fifth gear, just for reference. It really needs another gear.