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07 Silverado 1500 NBS Final Drive Ratio

Discussion in 'GM Powertrain' started by nkeen07, Apr 17, 2012.

  1. nkeen07

    nkeen07 New Member

    Hey guys,

    I bought the truck used w/34000 miles on it about a year ago and I'm unsure of what my final drive ratio is. I found something about the standard ratio on all Silverado 1500's in 07 being 3.42:1, but I'm unsure if my truck was special ordered w/3.73's or not. Mileage and acceleration lead me to believe I got stuck w/the 3.42's...but is there any way to find specs on what my truck came with? Unfortunately I don't have the window sticker or anything. If not, do any of you know what RPM I would be running at a certain speed and gear w/either set of gears and factory 31" OD tires? It is an ECSB 4WD/AWD LTZ. It does not have the Z71 package, but I know from some testing last winter that I do have a locking rear diff on it.

    If I do end up having 3.42's is it worth it to change out to 3.73's? What type of mileage hit would I take? I pull a 6x12 v-nose enclosed and will soon be getting a toy hauler bumper pull camper. I have a car to make my daily work commute during non-winter months, so a slight loss in mileage won't hurt me too bad.

    Thanks for any help in advance.
  2. 07XCSB

    07XCSB Active Member 2 Years 1000 Posts

    Look in your glovebox and match the RPO codes to one of these and that will be your rear gears.

    GT4 -- AXLE REAR, 3.73 RATIO
    GT5 -- AXLE REAR, 4.10 RATIO
    GU4 -- AXLE REAR, 3.08 RATIO
    GU5 -- AXLE REAR, 3.23 RATIO
    GU6 -- AXLE REAR, 3.42 RATIO

    ---------- Post added at 01:58 AM ---------- Previous post was at 01:52 AM ----------

    If you are going to regear, go 4.10's. It will pull your load alot better and you won't take that big of a hit on hwy MPG. My truck is a 4.10 07 Classic and when it was stock I was getting 16.7 in town and 20 on the hwy.
  3. Jeremy09LTZCrew

    Jeremy09LTZCrew Epic Member 5+ Years 1000 Posts

    It's all about the RPO. I wish they'd come stock with the 3.73, but I guess it doesn't really matter since I'll be regearing when I get the lift anyway. It's still enough to do anything needed right now.
  4. nkeen07

    nkeen07 New Member

    Thanks for the information! That is exactly what I needed. I checked and it looks like I have 3.73's and a limited slip.

    So, my question is: is it worth it to me to consider going to 4.10's? I still use the truck as a daily driver sometimes when I get tired of the gas saver. From what I figure, that would be about a 9% increase in RPM's at highway cruising speed (70-80 mph most of the time for me). I can see the effects going either way. With more mechanical advantage in the city the engine works less hard to get to speed from a stop. At highway speeds although the RPM's are slightly increased it could allow the truck to be in 4 cylinder mode more often as it requires less power to maintain speed. I pull my enclosed probably 30 times a year, but never any longer than a couple hour drive. When I get a toy hauler (half ton towable of course), I may take some longer trips to race GNCC's, so I have a feeling 4.10's would be very beneficial pulling that heavier load.

    Does anyone have experience w/4.10's and 3.73's and the differences that the gearing change made? Thanks again guys.
  5. 07XCSB

    07XCSB Active Member 2 Years 1000 Posts

    It's not worth the cash for such a little gain to go 4.10s. on stock size tires, plus if you do lift it and go bigger tires, worry about a 4.56 then. As long as you are rolling stock, keep what ya got and enjoy your truck.
  6. nkeen07

    nkeen07 New Member

    That's kind of what I was thinking. It wouldn't be much of a difference either way. I highly doubt that I'll do anything lift wise with this truck. I just don't like lifts or levels on 1/2 ton trucks for towing purposes. Thanks!

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