I plan on changing out my 3:55 gears to 4:56. I have 33" on my 2006 5.4 4x4. Right now I feel like the RPMs are way too low at cruising speeds. The reason I'm going with 4:56 gears is that I'm planning on getting 35" inch tires when the 33's wear out. For you guys that have done this, what brand of gears did you go with? I don't want to break the bank but I want something that's going to last. Also what kind of gas mileage would I be looking at?

 

What are your 60mph crusing RPM's now? What current gears do you have? 4.56 is a bit of a stretch for 33s...but to answer your question, yukon gear seems to be popular. Gas mileage will suffer because of the shorter final drive ratio.

 

Dang... did you even read his post ? He stated he had 3:55 gears now and wanted 4:56 cause he was planning to go to 35's.. X2 on the Yukon Gears..

 

Wow...I missed all that...must have been distracted lol my bad

 

lmao

 

With the gear and tire change your rpm will increase by ~20% at a given speed. Driving around with OD off will give you an idea of how bad your mileage will suffer on the highway. My guess is -2mpg.

 

Cruising at 60mph is about 1600 rpm. I'm sure the 33s are throwing off the speedo a little though.

 

Has anyone gone below 3.55 to get better milage on stock tires?

 

I think, more importantly, steeper gears will keep you out of boost and can actually negatively affect performance than some know. On most turbo applications, people are trying to use taller gears in order to get that boost up in order to aid in performance and maximize boost. Shorter gears can greatly cut down on your engine's ability to build that boost.

It's something to keep in mind. Yes, boost can cut down on your fuel economy, but you certainly don't want your engine falling on it's face switching gears so quickly that you can't built enough load to take advantage of the power your engine can create.

 

I've been curious how the 3.31:1 works out in real life...and the 3.15:1...wow, at 60 mph you wouldn't be turning many revs....