1968 350-2 : Gear suggestion

Discussion in 'Got gears?' started by 68 Skylark cust, Sep 15, 2020 at 7:04 PM.

  1. 68 Skylark cust

    68 Skylark cust French Canadian Member

    Hello Buick fellows , I am questioning myself about changing my diff gear in my 68 Skylark

    It has the stock 350-2 engine with a ST300 (2 speed automatic tranny) . The car was born with a 2.56 rear gear with 14'' tires. Now change for 3.08 with 15'' tires over the years.

    I'm not racing the car but I'd like to give it a little "help" to spin the wheels here and there (lol) while cruising it .
    Wonder what would be a good compromise with performance gain, fuel millage .. and rev noise (I have no tach)

    I forgot to say (if it matters) that my Canadian built car has a Chevy 12 bolts diff from factory

    Thank you
  2. philbquick

    philbquick Founders Club Member

    Put a 3.42 rear with a 200R4 in it.
  3. BrianTrick

    BrianTrick Brian Trick

    Are you keeping the 2-speed in it?
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    With 2.56 gears, 60 MPH is around 2000 RPM. With 3.08's, 60 MPH will be 2400. Steeper gears multiply torque, but at the expense of RPM and gas mileage. Have you optimized your ignition timing? That may give you the added ummmph you want without a gear change.
  5. SpecialWagon65

    SpecialWagon65 Ted Nagel

    The GS350 cars of 68 and 69 were equipped with a 3.23:1 rear.
    That has worked well for me- wagon and 69 GS350 run well.
  6. monzaz

    monzaz Jim

    your choices are 3.07 3.31 3.42 3.55 3.73 3.90 4.10 4.56 and beyond.
    you will need another carrier unless you want to use a ring gear spacer kit...which we have done many times for 12 sec and slower cars to save customers some money. (YOU MUST buy a kit that has the longer bolts or it will fail.) Other than that we have tested the spacers to 11.50 car and slicks with out issues. 4000 pound car.

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