Swapped factory 3 speed for close ratio 4

Discussion in 'U-shift em' started by Schu3507, Oct 3, 2017.

  1. Schu3507

    Schu3507 Well-Known Member

    68 Skylark. Came wt 350-2. 3 speed on the column. Was moved to floor by PO. Car has 41k stock 8.2 rear end.
    It’s a Saginaw 4 speed close ratio. I used to do 80-90 plus and was under 4K. I’m now turning 70 mph at 3k. Car screams around town and is a blast to drive.
    Tires 205-50-15s. Going to go wider not 60s.
    Any thoughts on gears from factory?
    Building 8.5 posi. Was gonna go 3.42s. I’m thinking 3.07s wt this close ratio. Thoughts?
     
  2. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    My thoughts are that in fourth gear with the 4 speed should be the same as in 3rd gear with the 3 speed because both should be 1:1.

    Not sure why your RPM are so much higher with the 4 speed on the highway? Is the clutch slipping while driving on the highway?
     
  3. Ziggy

    Ziggy Well-Known Member

    Top gear is the same 1 to 1 in both transmissions. Recheck your results.
     
    300sbb_overkill likes this.
  4. philbquick

    philbquick Founders Club Member

    A 3.07 and a close ratio trans don't go together, even with a 3.42 I'd go with a wide ratio trans. My Vette had a close ratio with a 3.70 rear and I didn't have enough 1st gear and it tached 3500 RPM @ 70 MPH. If you go with a 3.07 rear you will go through a lot of clutches with a close ratio trans, your car will be more fun to drive with a wide ratio trans.
     
  5. Schu3507

    Schu3507 Well-Known Member

    Re check results? I pretty much drive for a living for past 11 years. I’ve got video of going 80 at 3k wt three and 70 at 3k wt four speed.
     
  6. Schu3507

    Schu3507 Well-Known Member

    Doesn’t feel to be at all. It’s a new clutch.
     
  7. Schu3507

    Schu3507 Well-Known Member

    I can accelerate from 70 and be almost opening secondaries as I get into the pedal.
     
  8. Schu3507

    Schu3507 Well-Known Member

    Apologize for sounding arguentaive. Hard to relay my tone in text properly.
    Could it be because was one was Muncie and one is Saginaw or are both top gears one to one? The four speed may have be a jeep unit? There-for a shorter final gear?
     
  9. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Final drive gear all factory car non-overdrive transmissions should all be the same 1:1.
     
  10. Schu3507

    Schu3507 Well-Known Member

    If want I’ll send you videos? Im at a loss.
     
  11. Schu3507

    Schu3507 Well-Known Member

    The car is much more enjoyable to drive wt the four speed. I’m thinking take inspection cover off rear end and determine what I’ve got for gears. The. Build my new rear end wt same ratio. Just want posi and 8.5 rear end so I can obtain affordable gears and not limited to 8.2 prices
     
  12. Schu3507

    Schu3507 Well-Known Member

    Could my speedo be off wt diff trans?
     
  13. wkillgs

    wkillgs Gold Level Contributor

    Yes, that's it. The gears that drive the speedometer are in the transmission.
    If you change the trans, it may have the wrong gears for your rear axle ratio.
    You can use a GPS to indicate your actual speed.

    If you want the speedo to display accurately, you have to change the speedo gear(s).
     
  14. Schu3507

    Schu3507 Well-Known Member

    Right on!!
     
  15. Ant Legrand

    Ant Legrand Well-Known Member

    I think most factory equipped close-ratio trans cars had something like a 3.90 rear axle ratio. The higher (lower numerically) first gear in the trans needs that.
     
  16. Schu3507

    Schu3507 Well-Known Member

    What would a wide ratio 3 speed wt 350-2 barrel run? My car was orig until I swapped 3 to 4
     
  17. SpecialWagon65

    SpecialWagon65 Ted Nagel

    I'd have to double check - I think it would be standard as 3.23 :1. My 69 350/3-sp has that - great (to me anyway) compromise between 3:42 and 3:08.
     
  18. 87GN_70GS

    87GN_70GS Well-Known Member

    Gears for speedo in trans are not right
     
  19. schlepcar

    schlepcar Gold Level Contributor

    If that Saginaw trans is the one with three grooves on the input shaft,it has a very low first gear. You stated that you were revving three grand at 70 mph so you definitely want to check to see what gear you currently have. You may even consider dudding it down to a highway gear. For instance,if it currently had a 3:23,you may benefit from. 3:08. I would not go numerically higher at this point unless you just want to drag it. You are currently revving quite high and you stated it is a blast to drive as is. If it is a close ratio,low first gear trans,clutch wear would not be a problem even with a 2:73. Jack up one rear tire,spin it in two complete revolutions while counting the number of times the driveshaft turns. If it spins 3 times,you have a 3:00 ratio,2 and a half times is a 2:50 ratio(these ratios don't exist)but you get the idea. Just over 3 turns is likely a 3:08,three and 1/4 turns would be a 3:23.
     
  20. flynbuick

    flynbuick Guest

    Ted is right--a 3.23 rear gear ratio if it was standard.
     

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