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2K6Smoked said:
at 70 I turn about 2000 RPM's, and at 80 I turn just under 2500 RPM's.
Interesting, that is a huge difference to me.
2,500 rpm = 72 to 73 mph.

The needle is right on 2,500, and the speed is verified with a stop watch and the 1-mile markers, and ironically enough, the 72 to 73 is just about what the gauge is indicating.
 

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Quad T said:
Interesting, that is a huge difference to me.
2,500 rpm = 72 to 73 mph.

The needle is right on 2,500, and the speed is verified with a stop watch and the 1-mile markers, and ironically enough, the 72 to 73 is just about what the gauge is indicating.
Are you sure you aren't in 4th? 2500rpm at 72mph is way higher than what I'm at getting going 80. I'm usually at 2200-2300 at 80
 

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Here is what I get from calculating:

For Big Tow in 5th gear with 285/70/17 tires, Vehicle speed in MPH = .034756 x RPM

This means that Vehicle Speed/.034756 = rpm

80/.034756 = 2302 RPM

75/.034756 = 2158 RPM

70/.034756 = 2014 RPM

60/.034756 = 1726 RPM

The calculation is:

Speed = (Tire circumference x Engine speed) / (Transmission ratio x rear axle ratio)

Tire circumference = 102.758 inches / (12 x 5280) = 0.0016218 miles

You have to multiple the numerator by 60 to convert RPM to Revs per hour.

The denominator for 5th gear and Big Tow is (.834 x 3.357)
 

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I don't know I never drive above 65mph!

Actually, I see about 2000 at 70mph 2300 at 80mph. At 70mph up a steep grade at over 9500 feet I tach 2500, pretty amazing. These trucks just haul up hills!
By the way I love this site. I am brand new but have owned my Titan since May 2005. Traded my 2003 GMC Sierra for it. Should have joined sooner, I've been missing out. Read a lot here before I even purchased my truck.
 

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A little bit of tire difference can change things...with factory size 32's I'm 2000 rpm at about 70 mph...
 

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bestatchess said:
Here is what I get from calculating:

For Big Tow in 5th gear with 285/70/17 tires, Vehicle speed in MPH = .034756 x RPM

This means that Vehicle Speed/.034756 = rpm

80/.034756 = 2302 RPM

75/.034756 = 2158 RPM

70/.034756 = 2014 RPM

60/.034756 = 1726 RPM

)
That is the rpm I see , and my speedometer is right on according to my Garmin GPS.
 

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i'm non BT, but I thought I tell you guys my RPM anyway. 80mph @2400, seems high eh?
Do you have the Off-Road Package?...The O/R package has the same gears as Big Tow...
 

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OR pkg here, at 70 im about 2k, mabe a tad bit under.
 

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Yes, 2k rpms for me is about 70. I don't recall at 80, most of the speed limits around here are 60... so I try not to go 20 over... that... often... :D
 

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2000 at 70mph and 2300 at 80mph. anybody with big tow notice a drone from their exhaust between 50 and 60mph. sounds like the motor is sluggish to me, maybe I'll go get the timing advance done? I did it on my 04' 2wd KC and it made a nice differance.
 

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jasonmotox said:
2000 at 70mph and 2300 at 80mph. anybody with big tow notice a drone from their exhaust between 50 and 60mph. sounds like the motor is sluggish to me, maybe I'll go get the timing advance done? I did it on my 04' 2wd KC and it made a nice differance.
I notice a bit of drone at around 1700rpms under load. When it doesnt downshift and you gun it a bit, yeah it feels a bit sluggish to me as well.
 
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