I have a 2002 F150 4x4 5.4L with a 3.55 axle. Towing my current trailer is no problem, but since I want to move up to a somewhat heavier trailer I am thinking about changing my gears from 3.55 to 3.73 or 4.10. (I tow a lot in the mountains.) Are there any downsides to this that I should be aware of? Being somewhat mechanically challenged, what questions or issues should be brought up when I shop for a transmission shop? Reading the threads I gather I should avoid having the Ford dealer do this kind of work.

Bernie
Denver, CO

 

With a bigger gear in the rearend you will loose fuel economy. The bigger the rear end the more times the motor has to turn to achive one turn of the tires. It all depends on how heavy the trailer is and how much you are going to pulling it wether or not you need to do this. If you decide to change the gears go to a reputible shop and ask for references. If you have the right people do it you won't have any problems. If someone that doesn't have alot of experience do it they can really mess up your truck and have many problems down the road. If you tow heavy alot you might want to consider a bigger truck like a super duty, only if that is within your means.

 

You'll have to do both axles as well, so the costs will double.

You stand to lose mpg if you drive a lot of highway without the trailer. If you do city driving without the trailer, you may gain mpg...

Being a Colorado semi-native myself, I'll take this time to point out that limiting the size of the trailer may be to your benefit... especially when coming down off the passes. I get to hear every year about my neighbor's fun with brakes and broken suspension pieces. Choose the size of trailer wisely and don't overlook the brake controller.

-Kerry

 

actually - you WILL NOT suffer a drop in MPG due to the fact the motor wont have to work as hard as it had to with a higher gear ratio (i.e. 3.27s/3.55s)

what you WILL lose is top end...but who cares - its a tow rig - not a race car...id go 4.10's for sure, especially for towing in the mountains!! (unless you have a small wheel and tire setup) - in fact mine is going in the shop next week for that same thing!

however - with the added 'torquey' feeling - people tend to 'step on it' more - so there you WILL lose mpg around town without good discipline.

as for where do have it done...the dealership IS accountable - but expensive ($2000 for front & rear) - ask around - there is bound to be a reputable shop in your area that can do the work for a lot less (my local shop is doin' it for $1200)

good luck to ya!!

drj

 

Thanks for the comments. Currently I'm towing a 17.5' Bigfoot trailer that weighs out loaded at about 3800-3900#. I'm moving up to a 21' Bigfoot that will weigh loaded close to 5000# which is getting towards the topend of my towing capacity. I tow with an Equalizer wdh.

Bernie
Denver, CO

 

The equalizer hitch is great to tow with. Every since I switched from my 98 F150 to the F350 psd for towing I have been greatly pleased. You will have to see how your truck preforms with the 5000#s. There aren't a whole lot of mountains in Illinois so I can tell you how my 98 f150 did with the 24 travel trailer on them but it did do good on highway.

 

Driving habits have a lot to do with gas mileage, drj. You make very valid points.

Bernie, looks like you have it handled... I didn't see a controller, though. Good idea if you don't.

-Kerry

 

kspilkinton

i go camping up in arlington every summer for the NWEAA fly-in...i love the state of washington!!!!

 

4.10's would be my choice.

 

Prodigy controller

 

Anyone here have 4.10's or 3.73 in there 4x4 that they can contest to gas milage... its all speculation untill sombody who has tried it can tell us what these trucks will get on the high way.... im one that belives my 4.6 would do better with lower gears just for the fact that it works pretty hard to move its fat butt around... lol j/k but none the less it does work harder than i would like...so sombody who has gears should post some numbers for us to look at...
thanks
burnstoughford

 

Burns, you might need to post that as a seperate thread. Starting a thread outside of this one may get more exposure and give you more results.

Heck, outside of 7700s, and some of the factory tow packages in later stages of the '97-'03 body style, 3.73s and 4.10s weren't available even with 5.4s.

-Kerry

 

4:10 will give better mileage in the city worse on the hghway.3:55 to 4:10 will add 15% and bring your torque to 345 ft#.At 70 it will turn around 2300rpm.Tire/wheel size also has to be factored in.
Im going with 29" for fun.There are a ton of calculators for this on the web. If you don't like it you can get bigger tires next time around.I don't bother with the speedo just know the differance.I also don't know if i would bother on a 4x4 $$$$ So google it because all setups are a little diferent.
cheers

 

[QUOTE=matt_97xl]4:10 will give better mileage in the city worse on the hghway.3:55 to 4:10 will add 15% and bring your torque to 345 ft#.At 70 it will turn around 2300rpm.Tire/wheel size also has to be factored in.
Im going with 29" for fun.There are a ton of calculators for this on the web. If you don't like it you can get bigger tires next time around.I don't bother with the speedo just know the differance.I also don't know if i would bother on a 4x4 $$$$ So google it because all setups are a little diferent.Gears are the biggest bank for the buck on a 4x2.
cheers

 

the truth is - ANYtime your engine has to work harder to do the same amount of work - youre @ a serious disadvantage for mileage and for the life of your engine...

GEARS take back that advantage in YOUR favor - (it varies depending on wheel & tire setups) - but it is ALWAYS better for a large heavy truck with BIG tires that might even have to tow stuff - to have LOWER gears...the ONLY sacrifice is top end...period.

some of the LARGER trucks dont have that much horsepower...(even semis) - but what they do have is VERY low end gearing - and they actually get about the same mileage as f250 or f350...around 10-11 mpg.

drj