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...Raptor Slayer...
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So i have done a little research and found that some tundras have 3.90 4.10 and some have 4.30 gearing. I just called and with my VIN they said i had 3.90 gears and i run 35 inch tires and planning to run 37's. Im thinking that i need to upgrade to 4.30 gears from reading all the other threads but are the 3.90's ok to run with a 37's or do i need to upgrade and where can i do that?
 

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3.90 gears and 37" tires won't be much fun. There are no 4.30 gears that will directly swap into your 9.5" carrier. A rear differential from a 100 Series Land Cruiser will work, but an adapter for the driveshaft bolt pattern will be needed. Not a huge deal, it just hasn't been done yet. The front 4.30 diff from a tow package 5.7 truck should drop right in the front.
 

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I have 33" tires and 4.56 gears. this gave me the pep back off the line and a lot more torque in the O/D gear. My truck doesn't downshift when going uphill. You may lose a little gas mileage; but you have 35" tires!
 
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