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Discussion Starter · #1 ·
at what point of tire size should u change the Gearing? I have 35s and stock gears. i pull a 30ft weekened warrior about a dozen times a year. other then that i do good ol' Cali traffic driving.
 

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I run the same thing, 35's and stock gearing. I dont see a need to change the gearing. I never noticed any difference . My opinion is that if you were to go to 37's that would be a noticable difference especially with that 30' trailer. The key is to keep the truck in or close to the RPM range it is designed to work in .
 

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I have 35" tires and tow a 30' trailer I changed from 3.73 gears to 4.10 gears and it is now almost the same geometry as when it was stock, I think this is better, with the torque of these motors you will not feel much difference, but it is alot easier on the engine, especially the trans and fuel mileage when the geometry is close to stock. I say change them. Just my .02 worth. By the way I get 14MPG towing with the gear swap.
 

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Where are you in Cali? Iam in Sonoma county.
 

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With 3.73 gears on 35" tires you would be at an effective 3.3 gear ratio if you had 31" stock tires. If your stock tires were 32" you would be an effective 3.41. Little high for towing.

If your stock tires were 31" you would need:

4.10 gears would put you at a 3.63 gear ratio.
4.33 gears would put you at a 3.84 gear ratio.
4.56 gears would put you at a 4.04 gear ratio.

If your stock tires were 32" you would need:

4.10 gears would put you at 3.75 gear ratio.
4.33 gears would put you at 3.96 gear ratio.
4.56 gears would put you at 4.17 gear ratio.

Hope this helps.
 

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I too run 35's and I tow a 33' 5th wheel toy hauler. A little lower gearing would probably help a little but I don't feel like it's worth changing my gears. Plus with this combo I can cruise around 70mph at around 2k rpms which I like since 2k rpms seems to be the magic number to not pass when you're trying to keep your milage good.
 

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I ran 35" tires for 2 years w/ my stock gears and it wasnt' that noticeable. But when I went to the 37" tires I could really tell the difference so I went w/ 4.30s and couldn't be happier. How ever these gears are too much when I am running my 35" tires...
 

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hhrecovery said:
I ran 35" tires for 2 years w/ my stock gears and it wasnt' that noticeable. But when I went to the 37" tires I could really tell the difference so I went w/ 4.30s and couldn't be happier. How ever these gears are too much when I am running my 35" tires...
Was your stock gearing 4.10 or 3.73??
 

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That's the same as I have, but I'm an auto. I can tell a big difference with stock tires vs. 35's when towing...but I have tried them back to back.
 

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FIREBALL said:
I too run 35's and I tow a 33' 5th wheel toy hauler. A little lower gearing would probably help a little but I don't feel like it's worth changing my gears. Plus with this combo I can cruise around 70mph at around 2k rpms which I like since 2k rpms seems to be the magic number to not pass when you're trying to keep your milage good.
Did you recalibrate your speedo with the bigger tires? With stock 245/75-17 and 4.30 gears I tach 2250 rpms at 70mph and 2500rpms at 75mph.:usflag
 

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I have 4.10's now with 35" tires and I get 2k to 2100 rpm running between 70 and 75 miles an hour, at about 17mog, and my speedometer is off by about 2 mph, very close to stock geometry
 

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No, I didn't re-cal. I'm running 3.73's and my speedo is about 3-4 miles per hour off. I'm probably actually running a little faster than 70mph at the 2k mark.
 

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FIREBALL said:
No, I didn't re-cal. I'm running 3.73's and my speedo is about 3-4 miles per hour off. I'm probably actually running a little faster than 70mph at the 2k mark.
At just barely over 70MPH on the speedo I'm running about 78MPH on the GPS. I have 35's as well.
 

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I have 41" Iroks, and 4.56 gears,...but I also have a manual tranny w/ a SouthBend Clutch.
 

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I run 38's and 4.56. I tow quite a bit and quite heavy. I think 35's are the limit. If it was my truck I probably wouldn't bother. Anything larger and you should be looking at a gear swap. Driveability is improved, even when you're not towing. I found even with tuner and exhaust, the truck was lugging on the highway. I felt like you really had to lay into it to get it moving. It was a lot more fun to drive after the gear swap. My mileage went up less than 1mpg.


If you're not towing that often, I wouldn't worry too much about it. As others have mentioned 4.10's would work well for you and it would definitely take some stress off your tranny.
 

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I noticed a loss of power when I switched to 35x13.50 tires so I changed the gearing to 4.30 and love it. My power is back and it tows my 26' Weekend Warrior very nice.

Hey trkyhunter, I'm in Santa Rosa. Hi neighbor !!!
 

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Ive been debating on doing a gear switch myself. When I put the 35's on my truck I didn't think there was a noticable power loss at all. Now my dad has an all stock 250 with stock 31's on it and that truck runs circles around mine, I cannot believe the power differance. Not only is his truck faster, it conisitantly gets atleast 6-7 mpg better then mine.
 

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Discussion Starter · #20 ·
What do you guys think if i change the gears to 4.10s and then put my stock tires on (on ocasion to save wear and tear) and tow for a couple thousand miles? will that do any harm?
 
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