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What gears should I be running?

Discussion in 'The Garage' started by Mastiff, Aug 11, 2003.

  1. Mastiff

    Mastiff 1/2 ton status Premium Member

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    I've got 35" tires on my truck. Originally, I had a TH700 trans with the great overdrive, and I put 4.56 gears in (replaced the factory 3.73's). Now I have a TH400, so I'm spinning over 3K RPM on the interstate with no overdrive.

    The gears are great for everything except cruising, but it really sucks for that. Should I go back to 3.73, or maybe split the difference with 4.11's? What RPM does a stock 350 like to cruise at anyway?

    BTW, since a gear swap is out of my league, what would a typical shop charge for labor?

    Thanks for any advice!
     
  2. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    over 3000 rpm? what are you doing 75-80 mph? doing 65 you should be turning around 2800 rpm
     
  3. 88Silverado

    88Silverado 1/2 ton status

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    Heres a good link to see the diference of gear selection and tire sizes.
    Geartable

    The 700R has a .70 overdrive and a lockup converter. The TH400 doesnt, therefore you are going to spin higher RPMs.

    To change ring & pinion in both front and rear, your probably looking in the $500-600ish range.

    Tha 350 runs fine in the 3000RPM range. Gas mileage may suck but you wont hurt the motor.
     
  4. Mastiff

    Mastiff 1/2 ton status Premium Member

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    [ QUOTE ]
    over 3000 rpm? what are you doing 75-80 mph? doing 65 you should be turning around 2800 rpm

    [/ QUOTE ]

    I'd say I hit 3K around 60 MPH. Maybe the tires aren't really 35", or the non-lockup trans is slipping a little. Either way, it seems like it's screaming. Maybe it's okay. The people who wrote the gear table seemd to think 3000+ is no biggie.

    I think the truck cruised around 1700 in factory configuration. /forums/images/graemlins/rolleyes.gif
     
  5. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    [ QUOTE ]
    it seems like it's screaming

    [/ QUOTE ]
    do you have a tach or are you guessing?
     
  6. Mastiff

    Mastiff 1/2 ton status Premium Member

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    [ QUOTE ]
    [ QUOTE ]
    it seems like it's screaming

    [/ QUOTE ]
    do you have a tach or are you guessing?

    [/ QUOTE ]

    I have a tach.
     
  7. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Then your tires are short or your trans is slipping. 3000 RPM is fine but as you know the MPG will suck.
     
  8. Mastiff

    Mastiff 1/2 ton status Premium Member

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    [ QUOTE ]
    Then your tires are short or your trans is slipping. 3000 RPM is fine but as you know the MPG will suck.

    [/ QUOTE ]

    More likely it's because I never changed my speedo gear, so my speed numbers are all indicated, not actual (or would that make it wrong the other way?). Who knows how accurate my sunpro tach is either.

    Anyway, I'm hearing that most people wouldn't sweat it too much. It's probably not worth the cash to redo the gears. If I ever replace my axles, I'll go at least to 4.10.
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

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    It's your speedo is messed up. Your tach is perfectly accurate.
     
  10. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    With no O/D I really like 4.56s and 35s. It was just costing me too much when I went from a 15 mile commute to a 90 mile commute. It was my DD for a few years before I changed jobs.
     

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