Enter your username:
Do you want to login or register?
  • Forgot your password?

    Login / Register



    Results 1 to 6 of 6
    1. #1
      Join Date
      Apr 2010
      Location
      Jersey Shore
      Posts
      695
      Country Flag: United States

      Can a Ford 9" slip under load??

      working on a 55 chevy with a stock posi unit ford 9"... At 40+ mph, something will slip under a load, similar to a clutch that cannot hold power. I get no burnt clutch smell and the clutch is new with only break-in miles on it (~500 city miles of no hard driving). I have checked TOB engagement to ensure that it is not putting pressure on the pressure plate with foot of the clutch. The motor is nothing special, a stout 350, maybe makes 425 hp.



      So my test is this:
      I have an optical tach reading the driveshaft speed in 4th (1:1) gear. As I roll into the throttle and power band comes in, the driveshaft speed matches the engine rpm. There is a very obvious RPM increase as if something is slipping (its not breaking the tires loose either). Ive had some local guys tell me its possible with the stock style (cone?) clutch pack. I have never heard of a rear end slipping before? Whats going on here?
      -Chris
      '69 Corvette
      '55 Chevy Hardtop
      AutoWorks Middletown, NJ
      @autoworksnj for corvette and shop car pics
      https://www.pro-touring.com/showthre...e-Build-Thread


    2. #2
      Join Date
      Jun 2010
      Location
      Deployed
      Posts
      3,280
      Country Flag: United States
      A posi can slip, but never heard of such a thing while cruising. Additionally, one tire is locked to the carrier, you can’t have such a slip that no tires move. A posi simply turns into a one leg drive.
      1970 Camaro/DSE build


      Are you driver enough? Maybe....come on blue!
      https://www.pro-touring.com/threads/...71#post1147371

    3. #3
      Join Date
      Jun 2010
      Location
      Deployed
      Posts
      3,280
      Country Flag: United States
      A posi can slip, but never heard of such a thing while cruising. Additionally, one tire is locked to the carrier, you can’t have such a slip that no tires move. A posi simply turns into a one leg drive.
      1970 Camaro/DSE build


      Are you driver enough? Maybe....come on blue!
      https://www.pro-touring.com/threads/...71#post1147371

    4. #4
      Join Date
      Dec 2010
      Location
      Fredericksburg, VA.
      Posts
      3,155
      Country Flag: United States
      There is no possible way that the driveshaft can slip in the differential unless you have broken spider gears and in that case you would not be moving at all. Clutch smell or not your clutch is slipping guaranteed!
      Steve Hayes
      "Dust Off"
      68 Camaro

      Given sufficient initial acceleration, even pigs can fly!

    5. #5
      Join Date
      Apr 2010
      Location
      Jersey Shore
      Posts
      695
      Country Flag: United States
      We are going to pull the center section out of the rear this winter... Every time we test, it shows a driveshaft speed WAY higher than tire (vehicle speed) when the slip occurs. Spec Clutch also says that ALL of their clutch materials absolutely make an odor when the friction material burns. No carpet, or even shifter boot on this car yet and I cant even smell a hint of burnt clutch.
      I was ready to pull the clutch out of this car until I put the rear up and noticed that his rear was no longer a "posi"... Thats the only reason I even started looking at the rear and investigating the Ford style clutch packs. I will be just as surprised as everyone else if its the rear...
      -Chris
      '69 Corvette
      '55 Chevy Hardtop
      AutoWorks Middletown, NJ
      @autoworksnj for corvette and shop car pics
      https://www.pro-touring.com/showthre...e-Build-Thread

    6. #6
      Join Date
      Dec 2010
      Location
      Fredericksburg, VA.
      Posts
      3,155
      Country Flag: United States
      Please update this thread once you find the problem.
      Steve Hayes
      "Dust Off"
      68 Camaro

      Given sufficient initial acceleration, even pigs can fly!





    Advertise on Pro-Touring.com