I have a 2003 F-150 4x4 with an RCD 5" lift. I am currently running 33" BFG KM2 tires with the stock 3.55 gears and an SCT Live Wire tuner. My truck has 180,000 miles on it and I drive approx. 70 miles / day on the highway. I want to put on 35" BFG AT/KO tires, but I don't have enough money to upgrade to 4.56 gears right now. I know this has been done before, but with the amount of miles and the fact that I drive mostly on the highway, is it a good idea to drive with the stock gears on the larger tires. How long can I wait to do the 4.56 gears, or should I wait to get the tires until I can do both?

 

i drove with your exact setup with 35's for almost 4 years just fine. just make sure you have a transmission cooler and expect the truck to be slower.

 

Thanks str8t six! Your truck has come a long way over the years. It is one of my favorite trucks on this site. The only reason why I worry is because I have 180,000 miles on my truck and I don't want to risk trans. problems. How much did that built 4R70W run you?

 

I ran the same combo for years with no issues. I also did mostly highway driving with no heavy towing/hauling.

 

Thanks for the advice! I am gonna do it. I am gonna get the 35s and get the gears installed by the end of the year.

 

I'm running my truck with 3.55s still. It still works.