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Discussion Starter #1
so what do you guys think? the tire measures out to 32.7. how bad is it gonna be? best we can figure is at 70 its gonna turn around 2500 rpm.


not my truck, its a friends
 

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id say 4.10s but its his truck not mine
 

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GMC Owner
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i thought about swapping my gears out while i have my 285's because im eventually gonna do 35's.....but he'll prolly get worse mileage.
 

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Senior Military Member
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This forum has a double standard. They all say 4.88s+35s. Thats deeper then 4.56+285s.
 

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ive always said 4.56 for 35s and 4.10s for 33s. 285s are close to 33s. but you also that to gear more agressively the bigger the tire you go, it shouldnt be a flat curve, the actual rate of change should be increasing as well
 

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Speed Holes
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This forum has a double standard. They all say 4.88s+35s. Thats deeper then 4.56+285s.
yeah, everyone has their own thing.... but not only are typical 35's bigger than a 285, but also much heavier.

oh also, is the truck 4WD?


...all this talk of gearing in the past few months that I've been on this site it seems that there would be a solid Sticky gear thread by now.
 

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Discussion Starter #11
Well a member on here Ray has gears in his truck that he put to stock and is a smokin deal on
 

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Not that it matters, but my younger brother has an 03' F250 and recently had 4.56s swapped in and was running 38s. He decided he didn't like all the height and took the lift off and started running the 35s again, but kept the 4.56s in for about 2 weeks... It screamed while cruisin down the highway and was friggin awesome. Now hes got the original 3.73s and is puttin around like every other southcarolinian high schooler out there with the power strokes.
 

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GMFS slowest truck :read:
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id do it. would be fine when it comes time for real tires.
 

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Bayou Surface Drive, LLC
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IF that is the actual height Id run it. My old Remington Muid Brutes 35x12.50' were EXACTLY 32.75" tall mounted and I had 4.56's. I ran 2300 RPM at 70 with that combo. If the 285's are the nominal height wich i Belive it is those tires will actually measure out to 31.5" and then youll spin near 2500 at 70.

I have made a gear ratio calculator that is hosted on GMFS and it works great if you have Excel.
 

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Discussion Starter #19
the truck is a 4x4. the okie branch of gmfs is thinkin about takin rays runnin gear and putting it under matts truck. ray is putting his to stock to sell it. matt is on 285 that really do measure out just shy of 33". and he will eventually once his slack ass get outta school put on 35s. im pushin matt to do it. we were just a bit concerned with the now. but best math i can come up with is he is gonna run 2500 rpm at 70. and we are ok with that. just cant be any higher
 
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