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Discussion Starter #1
My truck seems as though it will not coast at all. Doing 70 MPH downhill I can take my foot off of the throttle and my truck will slow down very quickly. 7 seconds and I down to 50. In 10 seconds its down to 40 mph, then it will down shift and keep slowing down to a crawl. What would cause this?
 

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Discussion Starter #3
free wheels
 

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Discussion Starter #4
it drives like a stick shift. reminds me of the old sm465s in Chevy trucks.
 

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Discussion Starter #6
I tried that and the rpms dropped instantly. I think it's a combination of the torque converter not unlocking and the brakes dragging a little. So now what would cause the TC to not unlock?
 

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Sounds good to me rather then free wheeling... Make a difference using different chip files?

J
 

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mine does the exact same thing, no chip. never felt right to me, i've had it for a year. turning 2k rpm all the way down a 6% grade when it could be turning 1500rpm with no throttle input.
 

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Discussion Starter #11
I kept it in stock setting. Sausage450R that's exactly what mine does. I've owned a SD and driven a few OBS Powerstrokes and this is the only one that does it. it's a constant battle to keep it at highway speed. let off the throttle even slightly and it starts slowing down. I feel like its robbing my mileage. I'm averaging 13 mpg.
 

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Discussion Starter #12
Also to keep it at 70mph (with 285/75) I have to keep it pegged at 2118 rpm.
 

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Also to keep it at 70mph (with 285/75) I have to keep it pegged at 2118 rpm.
I think with 3.55 gears and 285s that sounds about right iirc. Try it with chip unplugged. Just remember to unhook batteries and no key in ignition when you unplug/plug chip into socket. You can fry PCM if key is in ignition (batteries hooked up) so best to unhook power totally.

jrc
 

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Unless someone has calibrated the speedometer, tire size isn't relevant to the speed displayed. 2100-ish RPM at 70 MPH is about where you'd be with stock tires (235/85). If you're still on the stock calibration, when your dash says 70 MPH you're really going about 72.5.
 

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Discussion Starter #15
these were gps speeds and digital read out from my Ford idle control box with 4:11 gears. But never the less everyone is pointing to the chip right now. I thought the stock setting was a bypass setting. Wouldn't that eliminate the chip? 13mpgs seems a tad low when my SD repeatedly got 17's.
 

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"Stock" is _supposed_ to be a bypass setting, but don't presume so. If you want to truly _eliminate_ the chip, remove it, just to rule it out (or in....). 13 MPG is way low, even for 4.10s.
 

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Discussion Starter #17
I was thinking 13 was low even for winter blend.
 

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Discussion Starter #18
Madpogue I'm going to owe you a beer haha
 

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Unless someone has calibrated the speedometer, tire size isn't relevant to the speed displayed. 2100-ish RPM at 70 MPH is about where you'd be with stock tires (235/85). If you're still on the stock calibration, when your dash says 70 MPH you're really going about 72.5.
Pending tire wear.

Not relevant? Please explain the context.... As I see it 265 tires roll more revelations per mile than 315s, so at 2100 RPM or any engine speed for that matter, tire size if very pertinent and will have a significant impact on what the "speedo" claims especially if the speedo is NOT calibrated to the tires.

j
 

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The speedo only counts revolutions of the AXLE, regardless of the size of the tire. Think about what your truck would do with no wheels/tires on it, and the axle tubes up on stands (in 2WD, of course...). You could put it through the gears, and the speedometer would go to, say, 60 MPH, even though you're going nowhere. With stock calibration, if you put stock 235/85s on it, in one minute the truck would go one mile. With 315/75s, it would go further. So the REAL speed would be faster. But the speedometer would still say 60 MPH. IOW, changing tire size would not affect the displayed speed, only the actual speed.

But the OP was going by GPS speed anyway.
 
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