Hello All,

I have a stock '03 F350 dually 6.0 and just bought a 40' 5th wheel that has a gross weight of 18k lbs. My truck has the 5 speed torque shift transmission with the "tow/haul" mode feature. The rear axle is 3.73 : 1 ratio.

Bottom line - my truck stuggles to pull my camper! Starting from a stand still the truck pulls off slowly and it does not matter if I use 50% throttle or 100% throttle the truck will only pull at the same rate - SLOW. After I finally get it up to speed the truck will drop gears like crazy at the slightest incline. the higher revs do nothing to prevent the rig from slowing down.

Using the 'tow/haul" mode seems to help pull better but the transmission begins to leak fluid like crazy at the rear of the tranny. Go figure! If you use the standard mode - NO LEAKS!m What could be wrong?

I have to make some changes for sure as the truck is a brake-down waiting to happen if I load the camper with toys. So is it possible to make my F350 pull better or cut the losses and upgrade to the F450 that the RV dealer told me I needed to pull my camper. I see many F450s with 6.0s so I think my motor may be good enough, maybe I need better gears like 4.10, 4.30s or new exhaust, high perf turbo, new software.

Can anyone shed some light?

Thanks,

OneTon4Fun

 

The 03-04 f350's trucks are no where near that tow rating. You are over by a few thousand lbs. I would swap a lower gear and a good custom tow tune if you really like the truck. As far as the leak on tow/haul, i know line pressure is increased when you are in t/h mode so maybe there is an issue there. A good tune can take the low end lag out of it. My turbo lag has pretty much disappeared with a custom tune from spartan diesel

 

Well you are overweight to start with, especially for those 3.73 gears!
Just know you are putting yourself and others on the highways at risk towing over-weight and you could get sued out of existance if you had an accident while towing all of that weight with the improper vehicle.... Ditch the F350 for a F450, but get one with a 6.0 for sure and with a 6 speed manual!! That setup should tow much much better!!

 

Like the others say, you are 6K overweight. You should have at least 410 gears. I'm not sure why you are push tranny fluid out the rear seal unless it is getting that hot and expanding. You would be much safer with a F450 and a manual trans. if you can make a good deal. Just my 2 cents worth.

 

Even if he is overweight the truck shouldn't have a problem pulling it I've had over 20k lbs on a 35' gooseneck (2 S250 bobcats) granted it didn't like it that much but it still did it without a problem and my truck is single rear wheel 3/4 ton with the 3.73. There is something wrong with your truck. How does it run unloaded? Could the trailer brakes be locked up?

You still need to get a new truck/trailer though or DOT is going to have a heart attack when they see you pulling that thing.

 

my uncle has the same truck, only 4.10 gears. he constantly pulls 20-25k. truck has just crossed 300k miles. pulls like a dream. you need new gears.

 

Weigh the truck and trailer on a CAT scale and see exactly what you've got. The GCWR on your rig is less than 23K so you're most likely overweight for pulling and stopping that combo.

Get that F-450/6.4/TorqShift and tow happily ever after!

 

If your leaking fluid in Tow/Haul mode.. No custom tune is going to help unless that tranny is fixed.. 99% of the time we increase the line pressures in the TCM when we build custom tunes for any use. So if you hit Tow/Haul, your line pressure increase X %, fluid starts leaking. You take a custom tune which by default increases line pressure X %, fluid leaks.. Hit Tow/Haul and line pressure increases 2(X %), you get massive transmission drowning..

Either upgrade to an F450 or for sure get that transmission leak checked, regear to 4.30 and do a little TLC to it..

 

DIDO- I have 4.30's, no problems with power.

 

I have an 06 F350 CC 4X4 tow boss dually w/4:30s and the auto. No problems at all towing my 3612 Raptor toyhauler w/4 quads and its all STOCK. Weighed at a scale coming home one trip at 24350. Dont be too concerned about your mileage with the 4:30s, my truck has just over 10000 miles and my mileage towing has ranged from 8.94 to 9.5.

 

Guys, this is great information. I see that I can modify my truck to pull my toy hauler until F450s become more affordable. The only F450s I have been able to locate are new ones that cost 50K or more! I love my King Ranch and the smell of this type of leather, a KR F450 costs 57K ! (way out of my budget) Besides the new Super Duty trucks have to be the ugliest truck I ever saw. I thought the Silverados were bad with the Chinese looking headlights. The new Fords look funky IMHO.

For those who are concerned about my overweight condition, I do not plan to travel much this year and certainly not until my truck is modified with air bags, 4.3 gears. Braking is not a problem, the F350 has ABS and my tri-axle RV has brakes on all wheels. I will plan to upgrade to the F450 ASAP

I will look into the lines around the rear of my transmission to see if a joint is loose. I do not understand why it leaks in T/H and not in standard mode. The transmission temp gauge is normal. Ambient temps outside were in the low 40s (nice and cool)

When the truck is not pulling a load it runs fine and accelorates good for a stock truck.

 

Hi Wodeman, I just bought a Weekend Warrior Full Throttle toy hauler. It is 40' and fully loaded with great features. I was not in the market for a TH. My wife and I are empty nesters and we wanted to get a 5W that could sleep 4 - 6 people. We have been looking for 3 years, when two weeks ago my wife and I were accoumpanyed by our son and his family, stumbled upon the weekend Warrior and that was it - everybody went nuts over this thing.

I did not plan to buy anything this big, I thought my F350 was more than enough truck for the camper we wanted. Now, I see the F350 is way short and even with modifcations I will not be without the possibility of fines and lawsuits if anything goes wrong on the highway. Even if my weight was not a factor.

Life is a classroom and we learn all the time, I will just have to upgrade the truck for the camper the family wanted.

One-Ton-4-Fun

 

The reason it's leaking in Tow/Haul mode is because the TCM increases your line pressure when it engages.... It's simple mechanics.. You run fluid through a line at a certain pressure and you get no leak.. You increase that pressure to a certain percentage and all of sudden you have leaking. Due to either faulty line or a line not able to handle that pressure.

In your case, you probably have a bad O-Ring..

 

Dont mean to hijack the thread but a KR 450 for 57k! No wonder we are shopping south of the border for trucks.I was at a dealer a couple weeks ago and the same truck lists for 73k in canada.

 

Unbelievebale prices!

73k in Canada = 74,728.16 USD

Both are outrageous.