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Discussion Starter #1
Not sure of my rearend gears, but at my normal 85-90mph highway speed I'm spinning about 2700-2850RPMs for over 100miles. Is this normal? Should I drop my speed a bit? Thanks.
 

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Other vehicle is an F250
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Look at the tag on the pass side of the rearend.Mine is 3.73.
 

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Heck dude?! Try to maintain just over 3000 RPMs. You'll get there sooner and the truck will have time to rest! :woot:
3000 rpms for 100 miles=GRENADE.
 

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powerstrokin
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what size tires are on your truck
 

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Here are the typical gears.

SRW = 3.73:1
DRW = 4.10:1
DRW Optional = 4.30:1

This is unless someone has altered it before you bought the truck.

My 4.30:1 gears with 245/75/17 tires = 2800 RPMs at 83MPH and it gets 13.7 MPG at that speed. Drop the speed to 65 and I get 17 MPG.
 

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Discussion Starter #12
Tires are 265/75/16's, I want to jump up to 285/75's next. I'm not in a hurry, thats just what everybody around here runs on the interstate! It just "seems wrong" to run an ENGINE almost at redline for so long....then again this is my first diesel, on the + side it sounds great with a 4" open turbo back at those speeds!!!! I get 18.5mpg avg most of the time, if I slow it down to around 70mph I get 20.4 avg.
 

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At 2k rpms, at right around 68,69 mph on 265s.
 

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85-90mph is not "normal" highway speeds.:hehe::hehe:
 
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