Guys, I added the level kit with the 3.55 gears and I have 305/55/20 10 ply tires so they are pretty heavy and I do a lot of hwy driving and the transmission keeps shifting to 5th at the slightest incline. Do I need to switch to 3.73 gears or possibly a different tire? It's pretty annoying that it does that.

 

A gear change will help with that. If your going to change gears go with 4.10 because your not gonna notice that much from 3.55 to 3.73's. I had a 2013 f150 4x4 with 3.73's 5.0L and the 6ps AT with 33's and it didn't shift down too much, but wish I had that little extra out of the hole power from the 4.10's

 

Thanks man! Did that eat up your hwy mileage at all? I bet I get around 15-16 right now. I did add AFE intake and Corsa Exhaust.

 

I didn't notice much change in my fuel mileage. But I did't drive it every day either.

 

I have the same configuration as you. I went with 275/50R20 BFG KO2's. They are quite a bit heavier than stock. I did notice it will downshift into 5th a little more often but not on slight inclines, it usually takes a pretty decent hill. I would guess your tire weighs even more than mine so that is the issue.

 

Post a pic of your truck. I'm thinking of adding a leveling kit and some bigger tires too. I'd like to see your setup.

 

The 5.0 is inclined to run a little higher rpm to hit the torque range. (compared to the eco's)

You have to go aftermarket if want to do 410.'s as the 373's are it for stock. Yes, the heavier tires are the cause. 10 ply tires weigh much more than your stockers. If most of your driving is highway and you don't tow anything heavy the 10 plys are an overkill. Your gas mileage will improve and so will the ride if you give up the 10's. Probably eliminate your downshift also.

If you want to keep everything the way it is and just try and eliminate the downshift give Livernois a shout and their tune will add the power needed to stop the downshift. The tune(s) will be way less expensive than switching out gears also.