RPM's
 

I have the 5r55e, 5 speed with od in my 04 3.0:

Cruising at 80mph I'm right at 3k rpm's. Is this normal?

Thanks!

That automatic should have these 5 gear ratios 2.47 / 1.87 / 1.47 / 1.00 / 0.75

.75 being OD

Look on the drivers door, back edge, for a label, find the AXLE code, it will have 2 numbers or a letter and number.
Last number is the gearing
_4 = 3.45
_5 = 3.55
_6 = 3.73
_7 = 4.10
These are the most common Ranger axle ratios

Measure your rear tire height

Go here: Engine RPM Calculator

Go to the lower calculator and enter the values
Like these
3.73 AXLE
27 Tire Height
80 MPH
.75 OD

= 2,785 RPM at 80mph

If I change tire height to 25 instead of 27 then I would get 3008rpm at 80mph

If I leave the 27 for tire height and change the AXLE from 3.73 to 4.10 then I would get 3,061rpm at 80 mph

So as you can see there are variables that only you know, or can get, that will tell if 3k rpm is "normal" at 80mph on your truck

Thanks for the awesome reply!

Mine is 7, so its the 4.10 and my tires are 28"

It seems to be pretty right, I should probably calculate the speed via my GPS and not the speedo as the speedo can be up to 5mph off sometimes!

Yes, I get 2,952rpms at 80mph with those numbers

4.10 is a pulling or hauling gear ratio, it generates more "pep" at lower speeds
3.45 is a Freeway gear ratio, lower RPMs at higher speed so better MPG, and less "pep" off the starting line.

If you had a 3.45 axle you would be at 2,484rpms at 80mph

On the Axle code the first letter or number tells you if you have a regular differential, OPEN, only one wheel gets power, or a Limited Slip, both wheels get power

87 or 97 = OPEN
F7 or R7 = Limited Slip(Chevy calls it Posi-traction)

Thanks Ron. I wish I had the lower ratio, but I bought it used. At least I know I can trailer my bike!

It is human nature to want what you don't have, lol.

Another fellow here , I think, has a 3.45 but wants to pull a trailer around for his business, so wants a 4.10, maybe you two should get together for an afternoon and swap axles, lol.
But IMO you are better off with the 4.10, pickup trucks are used more often to haul stuff vs just commuting to work on the freeway, but to each his own, which is why the 3.45 is offered, 3.08 was also offered, that would be 2,218rpms at 80mph, although you would be hard pressed to get rolling with any extra weight in the vehicle