csp9347

Hey guys. It was suggested that I move this thread over here to see if I can get more responses.
I have a stock 2010 fx4 Screw with a 5.4l, 373 rear end, 6 speed Auto and 275/55/20 tires.
I am planning on getting bigger more aggressive tires. I don't want to go with a lift, but will add the 2-2.5 inch level. I am probably leaning toward the 33"-34" tires.
My question is for those of you that have these bigger tires and the 6 speed transmission. Do you have a noticeable problem with your truck constantly downshifting or searching for the right gear?
And have you noticed a very big loss of power(acceleration)?

Thanks in advance for your help.

dicktracy09

Hey man, I have same year/motor/gears but with 275/70/18(just over 33's I believe), a leveling kit, and a SCT x3 tuner, K&N intake and muffler swap.

I know the tune changed the programming of my tranny and engine, but even before I had that, I cant remember any problems with the truck constantly searching for the right gear or downshifting(I had the bigger size tires then too) i will say that after the tuner, i feel the truck has a whole different feel to it. the tranny is smoother, the power is amazing(not that it was something to complain about before) and the overall driving experience is awesome.

hopefully that helps you a little.

csp9347

Thanks for the input. That helps - except now you've made me want a tuner too.

07F150Burnout

My buddy has a 2010 F150 Screw with the same gears and has a leveling kit and 35inch Nitto Trail Grapplers and his truck doesnt gear hunt at all, he also has a exhaust.

csp9347

Thanks. Nice trucks you have.

MR.FX4

I have the exact same truck with 34.5 inch trail grapplers and a 5star 93 octane tune. Yes the truck will down shift going up some Steep over passes, usually i think the torque converter just unlocks but it's nothing terrible. You will lose power if you go with a heavy tire like an m/t, i would suggest a lighter a/t unless you just want something knobby.

I highly suggest getting a tune with the tires, it gets most of the power and mpg back and fixes your speedometer, shift points, and eliminates the drive by wire throttle lag

Mlarv

No lift no tune a 4.6 3V with not sure of the rear end. I have put 285.75.17 I think on mine and have not noticed any problems at all. I am at work so I can't run out and check the size for sure. It still has plenty of power it never has searched for gears even when hauling a lot more then rated or pulling a little more then rated. Hope this helps

csp9347

I love the looks of the 295/60/20 that you have. I think that might just be a little more than I want. My truck never goes off road and I love the way it feels and drives now and don't want to lose that. I just want the look and the stance of the bigger tires. I am looking at the A/T tires, possibly the Terra Grapplers.

Stevegud1

To expand on all of this...I have a question. What all is involved with a shift point tune? Is it all CPU? My 6-speed auto tranny in the mountains of Pennsylvania really dogs, and seems to shift at EXACTLY the wrong times. This causes the truck to upshift just before hitting a hill, which slows it so much that it then downshifts just in time to go down the hill, and upshift again at the bottom of the hill. It irritates me, and uses up more gasoline than it should. BTW, the truck is mostly stock with respect to the drivetrain. Only change is I slightly went up in tire size (275/60/20 rather than the stock 275/55/20). It did this before I changed tires, too.