I have a 2004 Expedition, 4wd, 4.6L engine, 110,000miles and its paid for. My question is the max towing capacity is 5000lbs and I want to increase this to 7500-8500lbs if possible. I am in the process of purchasing a boat and this is the weight range of the boat that I would be towing. I don't want to purchase another vehicle for towing if I can just modify this one. I've done research on the power programmers, cat/back exhaust, and cold air induction kits as well as suspension and brake upgrades. Is it possible to increase the towing capacity of this vehicle to this range? All help and opinions would be greatly appreciated.

 

You do realize that you're trying to increase the manufacturer's tow rating by 2,500-3,500 lbs. or 50-70%. I don't know of anything out there that's going to give you that much of a boost while maintaining the integrity of the vehicle.

 

You didn't tell us if your XP had the optional heavy duty towing package, I assume it's not if you're quoting the standard tow weight of 5000lbs.
You also didn't say how long the trips might be and the weather.
Then there is the launch ramp, I know a lot about boat launch ramps - going down is the easy part.

My '00 A4WD has the HD Tow Pack and the max towing weight is 8000+ lbs (when new) - mine looks like a tank underneath.
The extras included in the Heavy Duty Towing Package include:
A heavy-duty V-5 rated Class IV trailer hitch with weight distribution capability, heavy-duty radiator, heavy-duty auxiliary transmission fluid cooler, hitch mounted 4 and 7-pin trailer electrics connector and factory prewiring for an electronic trailer brake controller module. In 2000 it also had the LLS system for side to side and front/rear load leveling. Mine has the 3.73 gears and your tires have to be load rated too.

Having said all that, my XP has 164k miles on it now and I still tow a TT that can weigh 5000 loaded, then load up the truck. Frankly I wouldn't want to tow any more than that. The advertised 260 horsepower 5.4 seems just about at it's maximum with that load, another real 50hp would be welcome.
I think you'd spend a lot of money trying to make your truck into a tow vehicle for that size boat.

 

Haslo,
The other guys are right on. Hopefully you have the tow pkg including air bags, because without, it's really pushing it. I used to pull my 24' boat (5,000# unloaded with trailer) with my 99 EXPY with the tow pkg and it was always a chore, especially going uphill, and that was with the 5.4, not the 4.6. Now we pull it with a F-250 6.0l PS and I almost don't know it's behind me. We got 15 mpg pulling it recently over the 4th of July weekend to Lake Mead. What a pleasure!!!
If you aren't in a hurry and you shouldn't be when pulling, you can get there but there's no replacing cubic inches. Remember you are on a F-150 frame so brakes, chasis, tranny, etc are not meant for this weight.
Save your money and get the right vehicle. You won't regret it.

 

I second r2miller's advice on getting the correct vehicle and I'm stating that as an RVer not an Air Lift guy. As an Air Lift guy, I just want to caution you against using air bags as a solution for adding tow capacity or GVWR just on their own.

 

I agree with the rest of the guys. You really need a V10 or a PowerStroke for what you want to do. You can get along with your present truck but don't waste your money on mods trying to make it do a job that it isn't designed to do. Save your money for the transmission that you will likely have to buy soon.

 

Mel,
You have a way with words. Well said.

 

Thanks, I'll take that as a compliment.
I try not to be harsh but the truth is the truth. I hope he is satisfied with the advice that was given by myself and the others here. A heavy load on an under powered vehicle is death to a transmission.

 

Yes, it is a compliment. How many times have we seen others try to make a vehicle something that it really isn't. Not many times have I seen them happy with the result and ultimately buy the "right" vehicle after spending money for the upgrades.