but It totally has to do with the ratio of rpm vs the speed of the vehicle?....if you change the gearing or tire size you effect the amount of rpms at every speed...so the rpm guage (and actual rpms read higher or lower than stock at all speeds)......Get it now?

 

if you read about 2100 rpm's at 70 mph you likely has stock gearing or gearing that offsets your different tiresize back to stock...

 

I run 265/75 r16's with 3.55 gears. I get maybe 14 highway.

 

I try to keep it under 2000 rpm, thats around 62 mph, just wondering what gears I have? Truck runs great, only 43000 miles.

 

really? so you dont drive above 62??...you would get ran off the roads around here...thruway is 65 and most do 75.......
try going to 2100 rpms for a minute and see what your rpms are...that will tell you if they are stock as long as the tire size is...

 

I usually going over 65, but to save gas I back down to 60 when I can. Morning traffic usually runs 60 or under, evening traffic runs 65-70.

 

Where are you from? Where I'm from, people do 80 on the highway at all times.

 

I turn 2000 rpm at about 72 mph, I have 265 70 16 tires and 3.55 gears, I average about 18 mpg if if keep it at 65, at that speed it only turning about 1800 rpms, but I have a 2wd rc/sb.

 

youre thinking of the speedo, cause the tach readsfrom either the cam or crank sensor, the speedo will read higher or lower depending on gears, and tires, the tach stays true. if you go to bigger gears(ie 4.10s) everything is turning faster at a lower speed, which obviously means the engines rpms are up and not down. which still leaves a true rpm reading. the speedo is the only one that changes

 

Roanoke, VA. Very polite people around here, moved from up north about 7 years ago, they will stop traffic to let you out!