Rpm's??
 

So its been about 8,000 miles since i got my gears changed from the stock 3.55's to the 4.56's that i have now and i dont remember what RPM'S i was running with those.

Right now i am running these...

45 MPH: 1,500
55 MPH: 1,700
65 MPH: 2,000
75 MPH: 2,500
85 MPH: ~3,000

I would like to get some comparisons from the 3.55 gears, the 3.92 gears, and the 4.11 gears

That doesn't sound too bad at all. What size tires? I'd probably say 2700 for 85 mph is ideal. I thought that's where you may be tad high. 65mph looks good.

my tires are 35x12.5

yeah they arent that bad but i just wanted to know what all the other trucks are getting.

And i getting about 12-13 MPG in the city and about 14-15 MPG on the highway

Can't speak for the others, but my 3.92 runs 2200-2300 at 75 MPH. At, 70 MPH about 1800.

I think mine with the 3.55 gears runs about 2100 at 75 and 1500 at 65. It sounds like i am running about 400 to 500 rpms less than you do through the MPH range. The worst gas milage i have got without pulling something is 16mpg and the best was 20mpg. I also am running the 17' rims with 285 bfg tires.

I run 1750 at 70 with 3.55 and 20s. 1850 at 75 & around 2000 at 80.

This sounds right to me.

As far as MPG, I get 13-14 and 16-18, 3.92's, 17's and stock 275's.

Pretty much the same here.

Did you do the gears yourself or the dealer? How much if you don't mind me asking, what brand etc. I need gears even 3:92 would make be happier, these 355 are nice on the highway but for take offs in the city you would never think this thing has 390 hp or 345 at the wheels as they say.

I had a place do the gears, it was ~2,000 for the front gears, rear gears, and rear LSD