I've got a 2004 F150 Screw, 5.4, 4x4, 3.55 rear end. Here is the situation:

Living in MS, we don't have much in the way of hills. I pull a 27' Terry travel trailer that has a dry weight of 5900. I had a surprise this past week when we made a roadtrip to the mountains of north Georgia pulling the fully loaded camper. Although I have the 'trailer towing' package, it apparently doesn't consist of more than the wiring harness, transmission cooler and brake controller harness. I now know I made a big mistake in getting a truck with the 3.55 rear end.

I need to do something to increase HP. I'm looking for recommendations that some of you have tried and are happy with (programmers, chips, exhaust, etc). We want to hit the mountains again but this rig really struggled. My budget won't allow for an upgrade to a F250 anytime soon so I'm looking to get the most out of this truck.

Thanks in advance.

 

I'd get steeper gears. You could mess around with chips, programmers and all that hogwash but gears would be the best bet if you are a tower eventhough the 3.55 is supposed to be the "towing" gears. If you are towing 6k LBS, 3.73s would probably be better fit.

Good luck.

 

Any modifications you do need to be things that will give you more torque. I won't go as far as saying horsepower isn't important in towing but you aren't trying to drag race.

Have you looked at the horsepower figures for the 6.0? It only has 325hp but the key is the 570 lb. -ft


If you plan on towing that much often just changing to 4.10 gears will help alot because it will allow then engine to rev faster. I have a gearing calculator link in my sig.

Electric fans and a computer tuner would also greatly help out with towing.

 

Those rock crawlers have super steep gears and are getting 10,000 ft/lbs at the rear wheels . But you probably want to go faster than 2 MPH.

4.10 would be pretty steep. I bet 3.73 gears with a programmer (to change shift points) would be a good compromise.

Horsepower is not a helpful number as it doesn’t really tell you anything. TQ is quantifiable. You can make it a towing moster with the right gears and shift points.

 

4.10s would be good for you, gear multiply torque.

 

My suggestions are change to at least 3.73 gearing or install a Postive Displacement Supercharger such as an Eaton, Autorotor, etc. (not a centrifigal as they are more for top end only and will not give you the low end grunt you need for towing). The SC would be more fun, but of course costly.

I have the factory 3.73s in my 05 Screw and also have them in my 2001 Screw. I have towed everything from 4500lbs of rock in the bed to 7000lb Bobcats on my car hauler (even towed a dead Tundra 4x4 Xcab on my car hauler :-) in the Western NC mountains (read very steep) with no issues at all. I am very familiar with the N.GA mountains as I used to live in Hotlanta and with 3.73s and 6000lbs you should be fine. Of course you won't break any speed records, but you won't clog up traffic on those roads either.

 

Sorry, repeat

 

As an additional note, I noticed that you have an '04; have you had it reflashed per TSB 05-10-12? This reflash will greatly improve the feel of the engine/tranny package when towing. It gives more power, better throttle response, firmer shifts, and allows the tranny to hold gears longer especially when it senses that the truck is under load. I had the reflash done on my truck and then hauled a Volkswagen Jetta from Philadelphia to Pittsburgh on the PA turnpike (Not exactly flat) soon after. The car/trailer probably weighed in at around 4500-5000lb, and I was amazed at how well it pulled it. Set the cruise @ 70 in Philly and it stayed dead-on 70mph the whole way to Pittsburgh.

I will also agree with having the truck regeared. I have 3.73's in my truck, and now that I just added 35" tires, I will be going to 4.56's. The good thing about gears is that they help to take some of the strain off of the motor while helping to multiply torque. If you just chip it, you are pushing the limits of the motor (timing, fuel curves) and causing the motor to work harder. Not that the motor can't handle the abuse (these are really tough motors), but fuel mileage will also suffer. Regearing to 3.73's or 4.10's will probably help improve fuel mileage a little while relieving some strain from the motor (gears + chip = EVEN BETTER COMBO!)

I will also have to agree that 4.10's would be the best choice for the load that you are pulling (I would go even lower if you plan on going with larger tires). Remember that if you order the optional heavy-duty payload package on these F-150's (7700# GVW) they come with 4.10's, so this gear is not too low for these trucks

 

Thanks for the replies. I'm thinking about starting with a tuner, see how that fits my needs and then make a decision on re-gearing. What I need to consider is the amount of towing that I will actually be doing. Will probably pull the camper 6-8 times a year. The balance of my driving will be dragging kids to grandmas house out of state. The 3.55 gears have been great for highway driving with no towing.

A question concerning re-gearing. I wonder if it would be more cost effective to just purchase the entire rear end (either 3.73 or 4.10) from a salvage yard (with a trade in on the 3.55 rear end) vs. re-gearing? I've read it can be very difficult to find someone who can set the gears properly. Something else for me to think about.

Also, someone mentioned that I can't re-gear the rear without re-gearing the front (since it is a 4x4). Any input?

 

>A question concerning re-gearing.
>I wonder if it would be more cost effective to just purchase the entire rear end
>(either 3.73 or 4.10) from a salvage yard (with a trade in on the 3.55 rear end) vs. re-gearing?

That would be my recommendation (but you must do front and rear), and since the 3.73 is very popular it shouldn't be hard to find a nice set. Your cost would also be reduced if you let them know you would like to "trade" instead of a straight purchase. I have done this many times very successfully.

While setting up a new set of gears is not "magical" and I have also done it many times, I am a firm believer that no one can do it as good as the original manufacturer under their controlled conditions.

 

That is absolutely correct...you have to change both axles to the same ratio, otherwise the front and rear wheels would be turning at different speeds relative to the transmission/transfer case, and it turn, hosing up your transfer case. You know the binding you feel when you make a sharp turn in 4x4? That is essentially the same effect, only not as pronounced as it would be with mis-matched diffs.

One other option, of course, is to never use 4x4!