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New transmission and gears in rear end

Discussion in 'Chevy Truck Talk & GM News' started by SavGaJoey, Dec 26, 2013.

  1. SavGaJoey

    SavGaJoey New Member

    I think I am going to have to put new transmission in my 2004 GMC Sierra SLE. I would like to put the most fuel efficient gears in the rear end at the same time, almost never tow anything. If I do it is a small boat for a short distance. How do I determine the best gear ratio for the best gas mileage? Is there any options on the transmission or will I be replacing / rebuilding what I have?
  2. McClintoc

    McClintoc Super Moderator Staff Member Platinum Contributor 1000 Posts

    Is your transmission going out? Does it actually need to be replaced or rebuilt?

    As for the rear end gears, what size tires do you have on the truck?

    As for the transmission, your only options are to rebuild or replace. If you replace, you can get a whole new transmission or you can replace your current transmission with another rebuilt one. Shop around for the best price on each option.
  3. SavGaJoey

    SavGaJoey New Member

    The transmission is shifting hard from 1st to 2nd, sometimes I have to lift my foot from the throttle to get it to shift at all. Never changes into the next gear at all. I am pretty sure the truck has a towing package which I am assuming would have be geared more to torque than economy. That is the only reason I am considering changing that while doing the transmission. I have P25570R16 tires all the way around.

    - - - Updated - - -

    Almost forgot, Check engine light came on about the same time transmission started acting up. It is on steady, not blinking and the truck has 170,824 miles on it.
  4. McClintoc

    McClintoc Super Moderator Staff Member Platinum Contributor 1000 Posts

    Reading the codes that tripped the Check Engine Light would be a good place to start. Most auto stores, like Pep Boys and AutoZone, should be able to read the codes for you.
  5. 99'HEARTBEAT

    99'HEARTBEAT Moderator Staff Member ROTM Winner Platinum Contributor 1000 Posts

    Before you do anything have your Trucks Computer Scan for the Check Engine Light, which your Local Auto Parts Ourlet, Auto Zone, O'Reillys will do this at no charge regarding the"The transmission is shifting hard from 1st to 2nd".....check out the the Link Below, it is about Transmission Trouble Code....P1870, which is a Harsh 1-2 Shifts.....on the 4L60E Transmission's

    Link,
    http://www.gmtruckclub.com/forum/showthread.php/54475-LOOK-HERE!!!-Trouble-code-p1870-for-harsh-1-2-shifts



    - - - Updated - - -

    Sorry, while I was typing, have your Truck Scan for the Code, you beat me to it....:lol:
    Last edited: Dec 26, 2013
  6. McClintoc

    McClintoc Super Moderator Staff Member Platinum Contributor 1000 Posts

    It's all good! Nothing wrong with a little confirmation. :)
  7. 99'HEARTBEAT

    99'HEARTBEAT Moderator Staff Member ROTM Winner Platinum Contributor 1000 Posts

    Good Deal.......:great:
  8. Rocketmanh5

    Rocketmanh5 New Member

    Yes 100% check codes. Does the engine have rough idle? Mine did this when I had random misfire problem with the afm junk. It would hold shifts for a while and shift relatively hard. Thought I was having tranny problems too but with all the computerized junk now days it's hard to pin point the issue like it used to be.

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