buzzard616
Medicine Hat, Ab, Canada
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Our TV is a 2008 Sierra 2500 HD 6.0L/6 speed. It came to us with 265/75R16 tires. OEM size is 245/75R16. This cuts my 3.73 gearing to about 3.58.
With an 8300 lb TT in tow, it can't quite seem to get out of 4th with any headwind or upslope at all. On level ground with dead calm or a tailwind it tows beautifully. Other people with the same truck and comparable trailers claim to be turning about 2200 RPM in 5th at 60 to my 3000 in 4th in most conditions.
I'm thinking that switching to OEM size tires would almost be a magic pill to get my truck towing properly. It would be the same as changing from 3.56 to 3.73 diffs.
Thoughts?
Stu & Jackie Metcalfe
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2008 Sierra 2500 HD gasser
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donn0128
Pronounced Ore-gun
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Taking it back to factory tire Ida is probably the cheapest way,to return its power when pulling. The other option of course is to keep the oversized tires and install a 4.10 rear end. On second thought are you sure you don't already have a 4.10 rear end under the truck?
Donn,Lorri,Max (The Rescued Lab)
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skipnchar
Topeka or somewhere else
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Joined: 12/17/2003
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What was the reason for the original tire change? Whatever necessitated it is probably still there. No doubt changing tires will help the power problem somewhat but then the original problem returns too. Keep in mind though that the gearing change you're getting is very small so don't expect drastic improvement but it MIGHT be enough that you can actually notice it.
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APT
SE Michigan
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You upgraded to the same size stock (31.6" diameter) I have with same drivetrain. I can hold 5th gear in most conditions letting speed drop up hills, but my TT is lighter by about 1500 pounds and probably shorter. I use Tow/haul mode and M5 on the highway. You might want to get the dealer to adjust your tire size.
A & A parents of DD 2005, DS1 2007, DS2 2009
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buzzard616
Medicine Hat, Ab, Canada
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skipnchar wrote:What was the reason for the original tire change?
Tires came with it along with lift kit (now removed) and macho rumble exhaust.
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SoCalDesertRider
SanDiego, CA, USA
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Joined: 12/14/2003
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I would just go back to the stock size tires.
If you want to keep the bigger tires, then change the axle gearing to 4.10, or more (4.30, 4.56).
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JIMNLIN
out here
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Ran some numbers for the 245 and 265 tires diameters. You will have approx 100 rpm gain with the 245 vs 265 at 60 mph (24xx vs 23xx RPM at 60 mph).
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers
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Turbo Diesel Dude
Green Mountain, NC
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I think your TT might be heavier than you realize (think). My 2011 came with 18" tires and 4.10 gears. The last two gears are actually TWO overdrives. You should get it weighed and you may find your problem. Not too much actual difference between 16"&17" wheels. JMHO
charles weidman
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APT
SE Michigan
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Honestly, the weight has little to do with maintaining 65mph on a flat highway. It's mainly aero drag. But the engine and trans computers think you have smaller tires than you have and are playing a factor with the shift patterns. 7% taller effective gearing will reduce wheel torque than lowering the engine speed by 7%. If you are due for new tires, go back to stock size. If not, get your computers re-flashed for the current tire size.
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Tombstone Jim
Tombstone Az
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Tires came with it along with lift kit (now removed) and macho rumble exhaust.
And I bet it had been chipped and had the dog snot run out of it. If it is really down on power it is something besides 1 in of tire size.
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