Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Curky, May 1, 2012.

  1. Curky

    Curky Epic Member 5+ Years 1000 Posts

    I talked to my buddy; he said he did not mention the 4.10 because I do way too much freeway driving. He wants me to write down what my RPM’s are at 25mpr, 35mpr, 50rpm, 60rpm, and 70mpr. I do drive about 50 miles a day freeway 65-70mpr (work), maybe 10-15 miles city (kids sports). He said it would be nice to have 4.10 but if we do everything we are talking about, I will get what I want out of it (more Power). You said you got more MPG? Do you know anyone else?
    Right now I get 14-15 MPG, if I just lost 1mpg. If it’s worth the power I will deeply consider it.
  2. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    I don't know others local to me who have regeared; most people lift and then put up with their trucks being sluggish (which baffles me). Heck, trucks lifted by the dealership are rarely regeared to handle the lift and big tires ... which is even more baffling to me.

    When looking at the ratio chart supplied by mfleetwood earlier in this thread be advised that it's intended for 1:1 ratios ... so it doesn't take into account overdrive. I used a similar chart to eyeball the gearing that I would need to get back to the equivalent of the stock performance that my 3.73's were giving me (with my stock tires) ... despite using larger diameter tires and gearing with a slight bias for performance over economy (which is also the bias my 3.73's had with stock tires). I then sat down with a calculator and did the math for a more detailed look at where my RPMs would be.

    Assuming a 1:1 ratio (i.e. not in overdrive), I calculated I'd be churning 29 rpm's more now, at 65mph ... than I did with stock 3.73 gears and stock tires. My combined mpg now ranges from ~14-16mpg depending on how much highway driving I do. Mpg is higher on the highway than in the city, as expected due to overdrive. Understand that the ~1.2-2 mpg I gained was simply mpg lost from aerodynamic changes caused by the the lift and subsequent removal of the lower front air dam, having 4 large/heavy tires on the truck, dropping out of overdrive on mild inclines as a result of both, etc. i.e. I merely gained back what I lost from mods (which was the goal).

    About 1/3 of my driving is highway, if that helps. All of this said, you need to go with what makes sense to YOU. We can recommend all day ... as can your buddy ... but ultimately it's your dime and your happiness on the line. You might want to take the chart mfleetwood provided and prove out where you want to be on it ... and do some additional math to make sure.
    Last edited: May 2, 2012
  3. 07XCSB

    07XCSB Active Member 2 Years 1000 Posts

    I know comparing my 93 to your 08 is like apples and oranges, but since the 4.10 install ,I have been getting 18 mpg local and 22-23 hwy. The truck doesn't have to work so hard up here in the mtns, so its getting better mpg. When it had 3.42s it was getting 15mpg local and 20 mpg hwy. I picked up 3 mpg across the board. Thats with a 31" tire
  4. Curky

    Curky Epic Member 5+ Years 1000 Posts

    Just heard this will affect my 100,000 mile warranty. As of 2013 it will be 5 years old so that is the end of the warranty anyway, Right?
    Do you know many people that have had to use the warranty?
    If it voids warranty, should I be worried? I only have 33,000 miles on it as of now.
  5. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

    I'm not aware of how many people have had powertrain issues covered under warranty but I can say that for those of us that realize that these types of mods could void a component's warranty have been willing to take the risk. IMO, GM makes a pretty solid product and most people find that the items covered under warranty far outlast the warranty term (miles or time).

    If you move forward with the mods, my recommendation would be to use quality products, ensure the mod is installed correctly, perform routine and preventive maintenance regularly, and couple with other mods needed to ensure the original mod is not causing damage to another part (i.e. large diameter tires need appropriate gearing) to provide you the best chance of keeping everything up and running properly.

    I'm not sure about this (and it will be pricey), but maybe if a dealership adds the mods, you'd still be covered under warranty....someone will have to confirm.
    Last edited: May 2, 2012
  6. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    When it comes to warranties I am conservative, as stealerships tend to blame anything they can in order to dodge warranty work. Thus, if it were my truck I'd hld off until the warranty expired. That said, it's -your- truck and you should take only those risks you are comfortable taking.
  7. Curky

    Curky Epic Member 5+ Years 1000 Posts

    Thank you. Well my fiancée still need to get a job. She just graduated from Pham. Tech school as soon as she gets a job and we get married in August, I can start my process and the rear and tires will be last from other mods. I figure that will be next summer. At that time my warranty will be gone.
    What I did figure out yester day. I was looking at the tag inside the driver door and it says my stock tires are 245/70/R17 rim 17x 7.5 J but I have 265/70R 17. I am assuming but I would have to say my speedometer is off and I lost some pick up. Am I correct here? The tires were on it when I bought it.
  8. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    1 person likes this.
  9. The Heater

    The Heater Rockstar 100 Posts

    The cutting off the muffler and replacing it with a straight pipe: OUCH. I highly recommend you rethink that one.

    There are a lot of things I like as far as modifications of a vehicle, but that much extra noise is not one of them. It interferes with talking, having some peace and quiet for just plain driving and thinking, it is a distraction (I don't need that kind of distraction) from concentrating on driving, and it really pisses off just about every driver around you.

    Even if you "think" you "won't mind" the extra noise from no muffler, I guarantee you will soon tire of it. Then you have to put a muffler on, costing you more money than if you just did the new muffler at the start.

    Lastly, that is not DOT approved and it is considered universally by all public safety entities and municipalities and highway patrol and sheriffs as defective equipment not to mention excessively noisy.

    I have to agree on the 4:10 gearing, if you are out to tow things. But your mileage is going to suffer noticeably.

Share This Page

Newest Gallery Photos