RPMs at 60
Elder User
Joined: Jan 2003
Posts: 851
Likes: 5
From: On top of a big hill...
Can't remember what it turns at 60 as I usually drive 65 to 70 on the highway. At 65 it's at 1700/1800 and at 70 it runs at 1900/2000.
It has 3.73 axle gears. Found if I keep the rpms at or under 2000 as much as possible I get an extra 1 to 2 mpg per tank.
It has 3.73 axle gears. Found if I keep the rpms at or under 2000 as much as possible I get an extra 1 to 2 mpg per tank.
Sit. Stay.
Joined: Oct 2001
Posts: 18,308
Likes: 20
From: Washington State
60mph in OD (.72:1 with the 4R100, ZF-6 & .71:1 with the 5R110)
w/3.73:1=1690rpm.
w/4.30=1948
w/4.10=1857
Thess numbers assume stock 265/75R16D tires and the 4R100 or ZF-6.
Straight from my Super Duty FAQ
w/3.73:1=1690rpm.
w/4.30=1948
w/4.10=1857
Thess numbers assume stock 265/75R16D tires and the 4R100 or ZF-6.
Straight from my Super Duty FAQ
Last edited by Monsta; Jan 16, 2004 at 12:44 AM.
Elder User
Joined: Jun 2001
Posts: 775
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From: Northern Va
Originally posted by camo4stealth
....The speedometer doesn't measure ground speed, but the speed of the drivetrain.
....The speedometer doesn't measure ground speed, but the speed of the drivetrain.
I agree and disagree. I am sure the poster meant actual speed, not indicated speed.
We all know taller tires will move the truck further each revolution, therefore changing the realized final drive, lowering the engine speed required achieve any given speed. If the speedometer is recalibrated for a taller tire, making indicated speed equate to actual speed, the engine will turn slower at 60 with a taller rear tire than stock.
Back on topic:
I am at 1900 at 70 with 3.73 gears and stock everything.
Last edited by CmprSpecial; Jan 16, 2004 at 09:31 AM.
Elder User
Joined: Dec 2003
Posts: 807
Likes: 1
From: Idaho
Can you recalibrate a speedometer with a stick? If not, it's not the indicated speed that changes, but the ground speed. I know with the auto, the speedo can be changed. I'm running about 2050 rpm at 70 mph indicated in 5th gear. With 285/75/16s I'm actually going about 71.5mph.
Elder User
Joined: Jun 2001
Posts: 775
Likes: 0
From: Northern Va
Originally posted by camo4stealth
Can you recalibrate a speedometer with a stick? If not, it's not the indicated speed that changes, but the ground speed. I know with the auto, the speedo can be changed. I'm running about 2050 rpm at 70 mph indicated in 5th gear. With 285/75/16s I'm actually going about 71.5mph.
Can you recalibrate a speedometer with a stick? If not, it's not the indicated speed that changes, but the ground speed. I know with the auto, the speedo can be changed. I'm running about 2050 rpm at 70 mph indicated in 5th gear. With 285/75/16s I'm actually going about 71.5mph.
I would check with a speedo shop, but I am quite sure they have an adapter for any transmission.
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Tuned
Joined: Dec 2003
Posts: 253
Likes: 1
Thanks for the info it was just what I wanted to hear. I guess I figure engine will last longer if it 's strong enough to do it's job at a nice moderate RPM.
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Sit. Stay.
Joined: Oct 2001
Posts: 18,308
Likes: 20
From: Washington State
Originally posted by camo4stealth
It doesn't matter, though, what size tires you have.
It doesn't matter, though, what size tires you have.
I'm running about 2050 rpm at 70 mph indicated in 5th gear. With 285/75/16s I'm actually going about 71.5mph.
Elder User
Joined: Jun 2001
Posts: 775
Likes: 0
From: Northern Va
Originally posted by camo4stealth
Can you recalibrate a speedometer with a stick? If not, it's not the indicated speed that changes, but the ground speed. I know with the auto, the speedo can be changed. I'm running about 2050 rpm at 70 mph indicated in 5th gear. With 285/75/16s I'm actually going about 71.5mph.
Can you recalibrate a speedometer with a stick? If not, it's not the indicated speed that changes, but the ground speed. I know with the auto, the speedo can be changed. I'm running about 2050 rpm at 70 mph indicated in 5th gear. With 285/75/16s I'm actually going about 71.5mph.
Laughing Gas
Joined: Oct 2003
Posts: 767
Likes: 132
From: Lynden, WA
I just had my dealer calibtate my speedometer due to tire size increase to 315x75x16's. Normally charges $75 for this but since I bought the truck there and worked this into the purchase price, he did it for free, just this once.
Junior User
Joined: Jan 2003
Posts: 78
Likes: 1
From: Derby, Kansas
F250 SD 4.3axle, V10. OD 60mph 2000rpm, 3rd gear 60mph 3000rpm. It drives this way loaded or unloaded. I think this where it should run. Pull a 9000# trailer in 3rd 3000rpm at 60mph so I'm satisfied.
Cheers
Cheers
