18 VS 23 Spline trans

  1. 18 spline

    35.9%
  2. 23 spline

    64.1%
  1. WRB426

    WRB426 Insane 4 Mopars FABO Gold Member

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    With a 500HP sm block in a street/strip car, is the 18 spline worth the extra cost?

    I think over time it would be. Would love to hear from 4 speed racers with their opinions.
     
  2. AJ/FormS

    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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    Street or race rear suspension? traction aider? Clutch/PP?
     
  3. RustyRatRod

    RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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    I think so.
     
  4. WRB426

    WRB426 Insane 4 Mopars FABO Gold Member

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    S/S springs, drag shocks, adjustable pinion snubber. No choice on clutch yet. Early start on build.
     
  5. RustyRatRod

    RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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    All that doesn't matter. The power and torque alone are enough to warrant the better transmission. Anything else is splitting hairs.
     
  6. WRB426

    WRB426 Insane 4 Mopars FABO Gold Member

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    This is what I think. I'm sure my mind is made up. Just have to bite the bullet and part with the cash.
     
  7. j par

    j par Well-hung Member

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    It hasn't been said here but I assume everybody's assuming that an 18 spline input is one thing i.e. 4th gear, but you have to have all the other hardened gears also which you really better be prepared to bust out your wallet! And unless you have some kind of OE restoration going on here you're probably going to find just stepping up to a jerico or something wouldn't be much more. Personally I would think a 23 spline will be fine on the street. Full drag slicks and lots of drag time over 500 horsepower ? Only time would tell... A rebuild kit is $99 plus whatever you break. Out-fixed- back in - over the weekend .....
     
  8. Ottmundr

    Ottmundr 68 Fastback

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    Seriously? 500hp? You're running a 360 stroker? No. What rear end are you running? I'm sure the 23 is PLENTY strong enough with an 8 3/4 rear end, other parts will break first. Spend that extra money on BRAKES, because you're gonna have to slow that beast down... Don't get drilled and slotted rotors, google stress risers.

    http://www.forabodiesonly.com/mopar/showthread.php?t=124884

    I hope I didn't come across as a dick, I'm just sick as a dog and grumpy today.
     
  9. RustyRatRod

    RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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    Chrysler obviously thought there was a difference. The Hemi was not rated at 500 HP and they all had the 18 spline transmissions where four speeds were used. Always somebody wanting to argue, but those are the facts.
     
  10. j par

    j par Well-hung Member

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    410 stroker about 425hp well built 489 case before and after about 30 drag passes ... dana 60 in the works....View attachment 20150430_154611.jpg

    View attachment 20151014_104921.jpg 23 spline 4 speed no problem
     
  11. 67Dart273

    67Dart273 Well-Known Member

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    Tire/ suspension/ launch / hook technology has come a long ways since those days, as well
     
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    • dodgedifferent2

      dodgedifferent2 Well-Known Member

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      I am honestly on this road at the moment.
      I have a 23 spline tranny in my 67 dart right now.

      I am thinking about an overdrive option and i keep looking at the 4 speed od from passon performance. The 4 speed from passon, as a gear set, only comes as an 18 spline.

      I already have the centerforce dual clutch which works awesome. It is the od i keep thinking about.
       
    • Dustert73

      Dustert73 Stripping bolts since ‘10

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      x2

      Assuming you have the money for it, why not just go to a brand new aftermarket trans?
       
    • Bonz

      Bonz Well-Known Member

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      I'll let you know how long the 23 spline lives behind my 470". 587hp/641tq.........:violent1::banghead:
       
    • 340doc

      340doc Well-Known Member

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      You asked for input from 4 speed racers, not sure if one has replied yet, I see a lot of speculation. Here's my 2 cents from 20 years behind a 4 speed. My setup was a street/strip 340, metallic clutch disc, running mid 11's in street trim, high 10's on a small spray kit. Car would hook solid. I broke anything that would break in the 8 3/4, axle, spider gears and the last straw was when I broke the ring gear after a test session before a street race. Upgraded to a Dana 60 with a spool. Problem solved. I'm sure others can respond with problems they had with there 23 spline but mine never gave me a bit of trouble. The only upgrade I did was steel shift forks, the brass tend to break with hard shifting use. I'm not out to argue with anyone, you asked so I'm sharing my experience.
       
    • j par

      j par Well-hung Member

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      Same experience x2. 4 speed racer , done with 8 3/4 going dana, just put steel shift forks in my 23 spline and it's really never given me any trouble and I've only abused it.View attachment 714.jpg
      18 spline is no guarantee ! !
       
    • WRB426

      WRB426 Insane 4 Mopars FABO Gold Member

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      500HP from a 360 stroker isn't a problem these days. Just ask Mike at MRL.
      And how do you know that I don't have a 4 wheel disc set up??

      And no worries I have thick skin. I asked for opinions so I get what I get.
       
    • WRB426

      WRB426 Insane 4 Mopars FABO Gold Member

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      WOW that"ll ruin your day. I've been thinking about Dana as well over the 8 3/4. I like to build it once and right.
       
    • WRB426

      WRB426 Insane 4 Mopars FABO Gold Member

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      Thanks for your input. This is what I was wondering if a beefed up 23 would be enough. Gave me something to think about.
       
    • Dartnut

      Dartnut Don't hate me because i'm beautiful

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      Go with the 18 spline and a Dana 60 rear end.
      You won't regret it.........
       
    • j par

      j par Well-hung Member

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      Actually my day was made the race before that happened when I put a Ford Mustang automatic on the trailer in the first round! But I have A post on the racers part of the forum as I build my "budget Dana 60"...
      I see it on the garage floor and get a chuckle - every part of the car is for my amusement \\:D/
       
    • rumblefish360

      rumblefish360 So close, yet so far away

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      The 8-3/4/DANA debate resides else where here. The bottom line is the 8-3/4 is fine for the street or light to medium racing. Nothing heavy duty. That's what a DANA is for.

      But since the thread is actually about the 4 sod trans spline count and its worthiness or not....
      I have had my E-body Cuda with a standard stroke 360 up and well over the 440HP mark and it is fine in the street with very little track use. Street tires and S/S springs, Centerforce Dual Friction clutch.

      I don't know where the "Give up point" is on these transmissions, but if it is going to be "Raced", a Jerico is a good idea. (Along with a DANA.)
       
    • AJ/FormS

      AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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      I have built many 23 spliners for 450/500hp STREET SBMs. None ever came back. zero. I think it's the guys that 60ft in the 1.6 or less, that need to worry.
      My 367 is fairly tame, at some where around 430/440 ftlbs. My best 60 ft (of 6 runs) barely got into the 1.9s. My 3.09low/direct 4th has got near to 100,000 miles on it, with lots of neutral drops at peak torque, and with either 295/50street tires or 325/50DRs. It"s still going strong. Street is easy on that 833.
       
    • efriedrich

      efriedrich 69 383S

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      A few years ago Wayne Brewer and I were having this same conversation and he told me that in stock form he didn't think there was much of a difference, we were standing in his shop looking at his RB powered 4spd race car and if I recall it had a 23 spline in it at the time. That's a pretty informed opinion....
       
    • Superod

      Superod Well-Known Member

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      Passon says the 23 spline is good for up to 550hp
       
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