Hi,

I have a 2002 Supercrew with the 5.4 Triton and 3.55 LS gears, stock tires, rated to tow 8,000 lbs. I use this truck almost exclusively to tow a Jayco Travel Trailer that weighs about 5300 lbs empty. I figure filled with water, clothes and food, propane, etc, it is probably another 1000 lbs, for a total nearing 6500 lbs. The truck handles the trailer well, but gas mileage is another issue. Consistently, If I tow around 55 MPH, I average around 10 mpg. If I tow around 65 MPH, my mileage drops to around 8 mpg.

I'm contemplating changing the gears, either to 3.73 or 4.10. I was leaning towards the 4.10 gears to give me more margin. The shop that I am contemplating do this work advises against 4.10, and is pushing the 3.73 gears. His reason? My gas mileage will drop too much with the 4.10 gears.

Anyone here have any experience changing gears from 3.55 in a tow vehicle and what was the effect on gas mileage?

Thanks
Mark

 

4.10'S will definitly help your truck while towing. 3.55 to 4.10 is really not as drastic a jump as you are being told it is. Go with the 4.10's.

 

I agree completely.

 

I tow a 6500# boat with my 03 sc with the 5.4 with3.73 gears and it seems to do alright. I'm not to sure on the gas mileage never really thought about it. I really didn't think I would get that great of gas mileage with a truck anyway.:o

 

i have a 2001 4.6 i changed from 3.08 to 3.73 i get almost 20mpg on the highway, i some times wish i had gone 4.10 but ya, i would go 4.10 for towing. It didnt seem like to much of a jump freom 308 to 373

 

Go with the 4.10s - I boubt the difference in MPGs between the 2 is that drastic.

 

I went from 3.31 to 4.10, huge performance increase with stock-sized tires...and I had a supercharger too. MPG didn't noticeably change.

I don't think you're gonna get much better than 10mpg while towing @ 55mph. And the MPG drop when you go to 60mph is expected...trailers are a huge aerodynamic penalty that gets worse as speeds rise.
But you'll have much better towing performance.

Consider your self lucky...I got 5mpg while towing my 8000lb toy hauler (towing mpg was closer to 10mpg without the supercharger). Boost will do that

 

I changed my gearing from 3.31 to 4.10 on my 4.6. the mileage when i towed a trailer varied from about 8-12 mpg. various altitudes. the change will definetly help pulling the camper. Another reason why they may be pushing the 3.73: i tried to get my pcm re programmed, and i was told by a dealer that they could'nt program a 4.10 gear ratio in my truck, only up to 3.73. so to solve that, i got a Diablo Predator programmer.

 

Just looking at the math - going to a 3.73 represents a 5% gain over the 3.55. The 4.10 represents a 16% gain.

Suggest that the majority of your mileage drop is due to the effects of the additional load and increased wind resistance - heck, you're towing at least another SuperCrew's worth of weight.

I've heard that an engine is most efficient when operated at its torque peak. Note that 'most efficient' does not necessarily mean least overall fuel consumption. But if you're going to be pushing the truck under load, it would be worth considering choosing a gear ratio that will put the engine near its torque peak at the speeds you want to run in order to get the best economy possible under those conditions.

All that aside, don't know that you'd feel a big difference with the 3.73 over what you currently have. I'd recommend going with the 4.10.