OK, many questions have been asked about gearing and tire size and RPMs while driving down the highway. I took a trip this weekend, actually, it was 189 miles each way. I averaged 17 mpg for the round-trip with my mods which can be seen in my sig. I'm still running the stock 3.55 gears with 265/75R16 tires. Here are pics from my camera phone while driving. I set the truck to cruise so you know im not letting off and its on relatively flat ground, not downhill at least. I have a 318 auto as well. Hope this helps out a little bit.


[IMG]local://upfiles/37884/873923E64F0E4CE9BDBB7564DA9BE330.jpg[/IMG]

[IMG]local://upfiles/37884/484A0D0850E84661A6647D6834470103.jpg[/IMG]

 

what mods did you make?

 

That's only about 200 rpm less than what mine runs at those speeds.

My truck has 4.10 gearsand running 265/75-17 tires.

 

I have a K&N Gen II CAI, Flowmaster American Thunder Dual Exhaust (40 series), MSD ignition, Royal Purple fluids throughout, thats all the performance there is.

Yea, so you can see that running the 4.10s will not run your engine too high like many people say. Also, a 35 inch tire on the stock 3.55s may be a bit too high for highway speeds cuz the RPMs will be low, out of the power band, causing lots of downshifting on hills. At least, thats what i assume would be the case

 

my foot doesn't go as fast as yours, but i turn 1500 rpm with speedo registering 55 mph, which is not correct. I'm actually going about 58. see tires below.