I have a 2012 F150 supercab 5.0 4x4 3.55 gears. I am thinking of changing gears to 3.73's to increase tow capacity to 9400lbs, and GCW to 15100 lbs per ford manual. Does this change make it legal for that tow rating on the road? Since this gear ratio is a factory available option on my truck. Any help with this will be appreciated.

 

What you're legally bound by are the axle weight ratings and the GVWR on the door decal on the truck. The GCWR is a Ford rating / maximum recommended towing weight. Stay under the GAWR on each axle and under the GVWR for the truck, and you should be fine. If you want to go strictly by numbers and stay in accordance with Ford's recommendations, then yes, stay at or under the GCWR. But from a legality standpoint, the GAWRs and the GVWR are the numbers you need to be concerned with.

 

Ok that is the number I will look at to see if they are the same between 3.55 and 3.73 trucks. Say if the 3.73 has a higher GAWR and GVWR and I change gears to 3.73 does that make me legal at that weight.

 

No it won't. Your GAWR and GVWR are stamped / printed on your truck and those are the numbers to go by. This discussion has been debated in the Super Duty forum and in here before. There are states which will allow you to register your truck for a higher or lower weight but from a strictly legal standpoint, the numbers the truck leaves the factory with are what you'll need to go by.

 

Thanks for the info. I should be fine then with a wd hitch and proper loading of truck and camper I should be under the gawr and gvwr. My campers gvwr is 7940 slightly over fords recommendations. I will see how it tows and if I am not happy with it. May just end putting in 3.73 to give some extra punch when needed.

 

Sounds good. You should also be able to lock out some of your upper gears too, if I recall correctly. Should help you stay in the powerband a little better.

 

Yes I do have the 6 speed select shift tranny. Which is sweet, that could cure the problem all together if I do have one. I plan on locking out 6th gear any how.

 

A gear change is a very costly endeaver, I would not waste the money if you are only going to a 3.73. If I were doing it and spending that money I would go with 4.10,,,

 

John is right on this you can't change the GAWR or GVWR it's set by the factory. One thing I have observed over in the SD line is if you take the tire weight rating times 2 you will come up with the axle rating (except for the DRW) so be careful when changing tires, if your tires are higher than the axle rating then you know that the axle is at its max.

I few years back I read how they come up with GCWR and its all done on a big hill towing wide open up and no trailer brakes on the way down. They try and see how much it will pull and stop before you destroy while it's still in warranty. I also noticed over the years the bigger the brakes the more GCWR.

Changing gears can be a real head scratcher, back in the years before OD you had to balance rpms and highway speed but now with OD and double OD it's easy. I would pull your rig with the gears it has and see how it works, if you want more power lock it into the first non OD gear and see what rpm gives you the best seat of the pants feeling . This is the gear you will be in on most hills and in heavy winds so you want to be in your power band. Then use a rpm calculator (go online) to figure the gear ratio that will get you close that rpm, I like to use 60 mph for my base speed, you will also need your tire diameter. With two OD you won't even notice the lower gears empty but you will pulling.

Last time I changed out 3.54 gears I went to 4.10 in a non OD F250 without any problems, I just had to watch my highway speed but the days of no OD are gone .

The 3 things I have learned in all the years of towing RVs and work trailers are Your brake controller is your best friend and a well geared level truck makes for a happy driver and truck.

Denny

 

Thanks Denny. I plan on pulling it a few times and a trip down to our huntin spot will surely test it. But not sure how steep of gears I will need. Will def. try you tip.