I have a 2006 F-150 5.4L V8 crewcab 4X4 with stock 3.55 limited slip gears. I'm wanting to get a 6 inch lift and 35's. I will be pulling a trailor some and off-roading some. Is it necessary to get new gears? If it is, What ratio and brand is best?

 

Go with 4.56 gears. Yukon is a good brand that I've used before. I would consider swapping out your LSD at the same time if you have one or adding one if you don't. I am getting ready to swap out my 3.73's on my 07 screw since the previous owner put a 6" Fabtech lift on with 35" tires. I will be going 4.56 gears with an Eaton TrueTrac front and back. Remember, you also will need a master bearing kit and I would recommend doing the rear axle seals and bearings at the same time.

 

Do you think I'll be ok to run 35's on the stock 3.55 gears?

 

It will be a dog and be harder on the tranny but you would not be the first to do it. I have 33's with 3.73 gearing and wish I had at least 4.10's at times but I do tow often.

 

I wouldn't go long term with that setup. At a minimum you want to have it programmed for the 35's otherwise you will put a strain on the tranny as it will think you are still running stock tires. As ab46501 said the performance will also not be optimal. On straight flat freeway it will feel fine. Any hills will really challenge it though.