re-gear questions for 08 Silverado

Discussion in 'GM Powertrain' started by canislupis69, Jun 29, 2009.

  1. canislupis69

    canislupis69 Epic Member 5+ Years ROTM Winner 5000 Posts

    Im hoping someone can give me some advice on re-gearing. I have an 08 Silverado 4x4 ext. cab with 5.3L V8. I have 7 1/2 inches of suspension lift and Im running 35 inch Toyo MT's on 20 inch rims. I have a catback flowmaster 1 in 2 out and a K&N CAI. I drove it on the highway for about a 6 hr. round trip and the transmission kept having to downshift when going up an incline. I have been considering re-gearing and have read on here to go with 4.56 gears. Does anyone know what this will do to my gas mileage and what kind of rpm's the truck will be running at highway speeds (70 to 80 mph)? Would I be better to go with 4.11's? My real concern is I do drive on the highway on small trips every now and then and do not want my engine having to run at 4000 rpms because the gears. Thanks for any help!
  2. rotaryenginepete

    rotaryenginepete Rockstar ROTM Winner 100 Posts

    do you have the 4 or 6spd tranny?
  3. canislupis69

    canislupis69 Epic Member 5+ Years ROTM Winner 5000 Posts

    Not sure...I will have to call chevy with my vin.
  4. canislupis69

    canislupis69 Epic Member 5+ Years ROTM Winner 5000 Posts

    I just checked with the is a 4 speed transmission.
  5. Ghostwhite

    Ghostwhite New Member

    Did you get any new info and make a decision? If you did what did you go with?
  6. grimreapersshadow

    grimreapersshadow Rockstar 100 Posts

    i would recommend the 411's the you will be turning around 3k rpms near 80 mph and thats not just hard on the trans its self but also on your fuel mileage ive been doin some homework about getting an 6 speed planted into my older chevy i all ready have the 456's front and rear and a full posi out back and its a gas hog once im over 70 mph
  7. caterpillarmx

    caterpillarmx New Member

    go with 4.11 gears

    i have the same set up 35 inch tires, 4.56 gears. 1st off the 4.56 gears cause the servcie brake system warning to be triggered. 2nd @ 65 mph i turn around 2100 RPMs. 3rd do you pull a trailer? 4th Gas mileage avg. is 14 mpg with Factory tuning & 13.5 with Hyper Tech Tuner installed.

    If i had to do it all over again i would install 4.11 gears.
  8. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    Ditto on the 4.11 gears. Shop around but the best prices I've found are at Randy's Ring and Pinion. They also have a lot of good tech on their website.
  9. masterfoxscout

    masterfoxscout Rockstar ROTM Winner 100 Posts

    I say go with 4.56s. I have them and love em!

    Caterpillar, are you still having issues with your Service brake light?
  10. canislupis69

    canislupis69 Epic Member 5+ Years ROTM Winner 5000 Posts

    I went with the 4.56's and love them so far. I have not had them on the highway yet though. My abs light does come on when driving now, but Superlift sells a product to fix that, I have already ordered it and Diablo is making a custom tune for my handheld to adjust for the gears, since their handheld only adjusts for tire sizes on the nnbs trucks.
    MasterFoxscout, what kind of rpm's are you running at 70 mph?

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