gear ratio for my build

Discussion in 'Got gears?' started by GMMADMAN, Mar 13, 2018.

  1. GMMADMAN

    GMMADMAN Well-Known Member

    Sorry guys, another gearing question. My 66 Skylark will be my play car that will see the occasional highway 60-75 mph. I don't really care about fuel economy at my ripe old age of 41, lol. I just bought a 72 Skylark non posi rear end with 2.56 gears that i want to re gear and add a posi to. I will be using the stock ST300 trans until I can get a 3 speed TH400 or possibly a built ST400, etc. I dont't have any plans to run a Gear Vendors OD. Anyway, I'm putting together a healthy 455 at the moment and I'm looking for recommendations on a gear ratio. I plan on fitting the biggest tire I can under the car with minor modifications. I was told that my Mike at TA that my 455 has the potential to be pushing over 500HP??? Thanks
    Engine specs;
    73 455 zero decked block
    +.040 forged pistons
    Torque plate bore/honed
    H-beam rods
    TA high perf oil pump assembly
    10.5:1 comp
    TA stage 2 SE assembled heads without additional porting
    Ta stage 2 SE 2" primary long tube headers
    3" dual exh
    Stock balanced crank, line honed
    TA 288-94H cam
    SP1 intake manifold
    ARP head and main studs
    800cfm Q-jet
    TA HD rocker assembly
    Stage 1 fuel pump and possibly an electric pump
     
    Last edited: Mar 13, 2018
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  2. Mark Demko

    Mark Demko Well-Known Member

    3.42
    Its a good compromise between acceleration and rpm on the highway.
    Its the lowest gear I would use WITHOUT and overdrive of some sorts:D
     
  3. BrianTrick

    BrianTrick Brian Trick

    I would stay in the range of 3:23,3:42,3:55.
     
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  4. bigce1972

    bigce1972 Well-Known Member

    I agree with both above. I put in a set of 3.42s last year with posi unit and really enjoy it. Noticeable difference in gas consumption on the highway compared to the 2.56s, but like you, I'm not on the highway too often so I can live with it. I'm happy with the decision for sure.
    Good luck,
    Craig
     
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  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    You can tune whatever gears you go with by varying tire height. Stock tire height is approximately 26.6”. Move away from that and the ratio changes. 3.73’s with a 28” tire is 3.55. 3.42 with a 28” tire is like a 3.23. 3.73 with a 26” tire is 3.82. 3.42 with a 26” tire is a 3.50.

    Tire circumference varies directly with diameter.
     
  6. monzaz

    monzaz Jim

    I hear the 3.08 is the way to go with all that torque I do not see much loss in 60 foot...Should see what is the max tire size before committing to a ratio.
    You also did not state a torque converter so that will make a difference also I would assume 2000- 2500 minimum stall.
    Remember the 350 or 400 will only give you more low end torque so depending on how long it takes you to make up your mind to get a 3 speed trans will be a determining factor again too.

    Personally I would not waste time just get going on the 3 speed trans bit the bullet your 41 already ...tighten up the belt and get it done NOW. you will enjoy your car much more and then for sure i would do the 3.08 gears.

    The only reason for the 3.42 gears is to over come no first gear. 2 speed trans basically is 2 and 3rd gears trans. Torque uis what makes any muscle car fun to drive. so that is what is going to give you the low end EVERYone is looking for. :)

    Jim
    J D
     
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  7. Dwayne B

    Dwayne B Well-Known Member

    I put in A 3.42 ,posi in my skylark, I really like it.I'm running A th350 ,and on the interstate it is as low as I would want to go.
     
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  8. Mart

    Mart '71 350 GS, almost stock

    I've run 390's with a turbo 350 and THAT IS the most I would go unless you do the 2004r trans. Fun ratio though....:D

    410's are better! Used to run 4.88 on street in 70.
     
    Last edited: Mar 13, 2018
  9. Dwayne B

    Dwayne B Well-Known Member

    I put A set of 4.10,posi about 2 months ago in my dad's v8 s10 with 5 speed, little truck is A hand full .
     
  10. Mart

    Mart '71 350 GS, almost stock

    Makes them fun. The way they're supposed to be...:D
    Ya don't wanna drive your granny's Buick do ya?
     
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  11. Bigpig455

    Bigpig455 Fastest of the slow....

    I've got a 65 Gran Sport with an ST300 and I've run it with 3.08's, 3.23's and 3.42's. You've already got advice about all the relevant decision points - type of driving, tire size, etc..,my experience is that 3.08's were fine with the ST300, and the car would still break traction from a roll .

    3.42's are a bit revvy at 80 MPH but the car 60ft's in the 1.9's with whitewall tires. 3.23's were the best of both worlds, and if I had to pick one and stick with it, it'd be 3.23's..
     
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  12. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Put the 3.42 gear set in and run a 28” tire. That figures out to 3.24.
     
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  13. BrianTrick

    BrianTrick Brian Trick

    I am building a 3:73 rear for a member on here. He currently has a 3:42,and is satisfied with how it drives with that,but he finds himself putting shorter tires on it,at the track,to get a little more out of it,so he wants to leave his 275/60/15 on all the time,and just bump up the gear.
     
  14. Bigpig455

    Bigpig455 Fastest of the slow....

    Excellent points - I was limited to a 26.7 inch tire by PSMCDR rules
     
  15. GMMADMAN

    GMMADMAN Well-Known Member

    I would love to run a built st400 from tri-sheild. Maybe I'll try the 3.42's with a 2 speed. Do you happen to have some 3.42's for sale?
     
  16. Bigpig455

    Bigpig455 Fastest of the slow....

    Check with Monzas above, he often has 8.5 3.42 and 3.73 gearsets for a reasonable price
    i
     
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  17. Buickboy69

    Buickboy69 Active Member

    I'm currently running stock 3.08s on my 72 skylark with a 215/60r15 tire and a th350 trans car averages 15mpg but it's a 350 car I still feel like the 3.42 or 3.73would be the better choice for any sort of drag race duties.
     
  18. monzaz

    monzaz Jim

    You would probably be correct...All depends on how much time you spend getting to the track as to the ratio you should pick and or the ET you wish to run...or which ever is most important to you personally. Jim

    J D Race
     
  19. monzaz

    monzaz Jim

    85.00 we have GM good used gears. No break in time with used gears. get them in and run em
     
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