Is this too much Gear for my application. Street Car

Discussion in 'Got gears?' started by mummy68, Nov 15, 2017.

  1. mummy68

    mummy68 Silver Level contributor

    I have a 68 Skylark with 1971 455 engine. A new th400 tranny and a 2500 stall converter.

    I have a chance to grab a Chevy 12 bolt posi rear end with Richmond 4.11 gears. I am wondering if this is too much for my application and how it would affect drivability. Strictly a street car but I am trying to complete my drive line and get good performance
  2. gstewart

    gstewart Well-Known Member

    Way too much gear for street driveability. Maybe a 3.43 would be better for u.
  3. TrunkMonkey

    TrunkMonkey Well-Known Member

    Back when Sammy Hagar was getting into trouble, four'levens were fine, now that everybody is pushing 80s, dogs will howl at the engine whine.

    Unless you have a future with a 200R4, you might like about a 3.08.

    I ran a 3.08 with a small block Olds (330) 40 years ago, and it was happy at 70 all day long, but IIRC it was running around 2200-2300 RPM.
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    BBB's are torque engines, they don't need deep gears like that. You will actually hate that gear on the highway, and yes, street cars do go on the highway.:)
  5. BrianTrick

    BrianTrick Brian Trick

    The most you would need is a 3:73,but a 3:23,3:42,or even the new 3:55 will be plenty,and yet drive anywhere.
  6. Oldskewl59

    Oldskewl59 Silver Level contributor

    I have the 3:55 gear and I like it, but it isn't great for the highway and it really hurts MPG.
  7. Mark Demko

    Mark Demko Well-Known Member

    I agree with all of the above.
    In my experience, a 3.42 gear is the deepest I'd run with a direct drive (1 to 1 in high) trans.
    Any deeper gear I'd want overdrive:cool:
    I have 3.42 gears in my '71 350 GS with a T-350 trans, the engine runs around 3200/3400 @ 70 to 75 MPH, I'm not concerned, but I'd be happier with it running 2800/3000 at that MPH.
    The Buick 350 and especially 455, can haul the mail with less gear than other engines:D

    BUICKRAT Torque Rules!

    If that 455 is basically stock, you will blow it up with 4.11's.
  9. BrianTrick

    BrianTrick Brian Trick

    I run a 3:73 with a 28” tall tire,and it runs about 2800rpm ay 60mph. I had to play with a few different converters to get the best of noth worlds. Either way,any big block does not need 4:10’s,or even 3:90’s for that matter.
  10. wkillgs

    wkillgs Gold Level Contributor

    I had 4.11's in my blue 66 until last year, when I switched to 3.42's.
    Worked great on the track or street, biggest downside was it limited my highway speeds to about 60 mph @ 3000rpm. That was fine when speed limits were 55, but not these days when 70-75 mph is the norm.
    If you are racing in the 1/4, you need to consider the max rpm you want to see. 4.11's will put you around 6,000 rpm for low-mid 13's.
  11. pbr400

    pbr400 68GS400

    My ‘68 has 2.93s and that’s great for all around driving-it’s quiet, feels strong, is never in the wrong gear, and I’m not afraid to hit the interstate for an hour or more. I also get about 15 mpg on the highway. A friend once had 3.90s in a similar car, and it was balls out crazy on the street from a roll, but above 60 was a lot of noise and thirst. I agree with the earlier post, without overdrive anything above 3.23-3.42 is unpleasant.
  12. wkillgs

    wkillgs Gold Level Contributor

    And find out what carrier that 12 bolt has. The 4 series carrier only accepts 3.73 & up gears. A swap to different gears may require a new carrier.
  13. mummy68

    mummy68 Silver Level contributor

    How about a 3.23 8.2 10 bolt posi rear from a 69 Pontiac Grand Prix. Will this do the trick.
  14. BrianTrick

    BrianTrick Brian Trick

    Some of those GP’s have a 12-bolt Chevy,but that 3:23 8.2 might not be bad. If you car is more of a cruiser,you will be fine. I would still go through it and freshen it up before installing.

    I have an LO-code 2:73 posi in my silver 70 GS,that I will be removing at some point.
  15. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    I run a 4.56 gear and it cruises at 80 MPH just fine... 33 inch tall tires though. It does try to rip your head off when you accelerate.

    Attached Files:

  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I'm sure it cruises 80 MPH just fine at 4000 RPM.:):)
  17. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    2600 Rpm at 80 with lockup torque converter and 2004R... At 120 it buzzes the revs a bit but it sounds good. It is only 2980 pounds so it does not take much throttle to hold highway speed.

    My old skylark had a 3.42 gear and a 2004R and it was a blast at 140 mph, was also twin turbo 350 car.
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    You left out the 2004R transmission. Kind of misleading, don’t you think?:rolleyes:
    Last edited: Nov 17, 2017
    Mart and Ken Warner like this.
  19. wkillgs

    wkillgs Gold Level Contributor

    And I'd say the gears have less to do with the 'rip your head off' than the the DUAL TURBOS you forgot to mention!:D
  20. 69GS400s

    69GS400s own amusement ride!

    Stock 10 bolt will not live long behind a warmed over 455 with any beating on it .. especially hard launches.

    .. BigRed ate 3 of them before I said "F"it and built a stout 12 bolt to handle the punishment. A 71-72 corporate 8.5 is a better investment than an 8.2

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