Engine RPM's at Various Speeds
 

Perhaps you guys could help me out with some general info. My truck is XL trim and it didn't come with a tach (still waiting for white face guage kits for that dash !!!) so estimating RPM's is very difficult. Anyway, I'm just curious what RPM's your guys' engines are turning at 55, 60, 65 and 70 mph in overdrive and out of overdrive. I'm just curious for towing . . . the RPM's I would be truning at various speeds, etc.

Thanks in advance

p.s. 1997 F-150 4x4, 4.6L Auto, EC, SB, 3.55LS, LT 245/75R16's, K&N Filter, Cat Back Exhaust

Check out one of the calculators on the web. I'm fairly sure Richmond Gear has one on their website. richmondgear.com. You can punch in all your info and go from there. I would actually measure your tire height. I've seen that the "same size" tire isn't always the same size.

Cougar Guy,

My truck isn't 4X4 but I have the same engine and rear end. My tires are 255/70R16 which means my tires are lower profile than yours and spins faster. But just so you have a ball park figure my engine is turning about 2,100 @ 70 mph and 2,200 @ 75 mph. It doesn't matter if I'm pulling my 5X8 enclosed trailer or not. Once I get up to speed those are my numbers or at least pretty close. Sorry I really don't pay much attention below 70 mph. On my way home from work tonight I'll see if I can notice unless someone else comes up with them before then.
I agree with Signmaster and try those websites. Heck I may even give it a try.

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F150IslandBoy
1997 F150 Lariat
SuperCab, Toreador Red w/ Gold, Styleside, 4.6L, A/T, A/C, 3.55 3800 Limited Slip, Class 3 Tow Package, Leather Captain Seats, Sliding Rear Window.
Modifications:
Airaid FIPK, Flowmaster Delta Flow 50 Series, Bugflector II, Viper 500ESP Alarm, Pendaliner Bedliner, Cobra Trapshooter 3 Radar Detector, CARR Tubular Nerf Bars, NFA 1400 Compact 55W=>85W Halogen O.E. Lights, Durango 255/70R16, Chrome eyelet tie downs, Smoked front lic. plate cover.

Thanks for the info, I'll check out that website.

Later

Excellent, I love formula's !!!

You do have a tach if you have a digital odometer. Follow the instructions on this webpage http://www.mustang*********/ourpics/fcar/dtcodes.htm For some reason it wont let me fill in the stars so you can. After mustang its w o r l d . c o m no spaces
99 F-150 Sport XLT Black x-cab 4.6L auto 3.55
K&N filter and dual series 40 flowmasters

[This message has been edited by this-end-up (edited 09-19-2000).]

[This message has been edited by this-end-up (edited 09-19-2000).]

[This message has been edited by this-end-up (edited 09-19-2000).]

You can make your own calculations with the following formulas:

MPH x Transmission Gear Ratio x 336.14 x Axle Ratio / Tire Dia = RPM
RPM x Tire Dia / Axle Ratio / 336.14 /Transmission Gear Ratio = MPH

Unfortunately, my odomoter is not digital . . . my truck is a 97 and didn't come with it.

Oh well, that's life I guess . . . now I have to sharpen up my pencil and calculator . . . or get a tach put in . . . any suggestioins?