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    Results 1 to 7 of 7
    1. #1
      Join Date
      Aug 2004
      Location
      Holmes Hollow, Ontario Canada
      Posts
      991

      my first posi fluid change

      I've got a 8.5" gm posi. I've got synthetic gear oil and 4 oz of limited slip addititive. Two questions:
      1. Should I be using synthetic?
      2. Do I use all the additive?
      thanks guys
      Scott

      ____________________________________________
      Scott


    2. #2
      Join Date
      Dec 2006
      Location
      So Cal
      Posts
      920
      1.) No.

      I just recently had an 8.5 built by a pro for my Tempest with a new Eaton posi, the builder specified that no synthetic gear oil be used.

      2.) Yes.
      Bart F.


      '64 Tempest - LS3/4L70E - Grandma's Poor-Touring car
      '64 GTO - 455 HO/TH400 - Ex-bracket racer, street bruiser
      '02 WS6 convert - LS1/4L60E - Pure stock, pure pleasure

    3. #3
      Join Date
      Nov 2006
      Posts
      456
      I've been using Amsoil synthetic oil in most of the rear ends that I have built over the last 13 years with no problems at all. If you got the GM additive then use it. If you got something else then take it back and get the GM additive.

    4. #4
      Join Date
      Jun 2001
      Location
      Newbury Park, CA
      Posts
      5,821
      Country Flag: United States
      bgh,

      For those like myself using a synthetic rated for positraction use, if there are no chattering problems are there any needs/advantages to using an additional additive package, i.e. GM fluid?
      VaporWorx. We Give You Gas http://www.vaporworx.com

    5. #5
      Join Date
      Nov 2006
      Posts
      456
      If you don't have any chatter then don't use the additive. The additive only makes the clutches slip easier. For performance applications you want the clutches to lock up as much as possible. The additive will only hurt you in a situation like that.

    6. #6
      Join Date
      Oct 2004
      Location
      Papillion, NE
      Posts
      203
      Quote Originally Posted by big gear head View Post
      If you don't have any chatter then don't use the additive. The additive only makes the clutches slip easier. For performance applications you want the clutches to lock up as much as possible. The additive will only hurt you in a situation like that.
      Keep in mind that is at a cost of increased clutch wear which eventually means no more posi.

      Clutch grip is almost entirely based on pressure of the beveled gears pushing outward on the clutches. In my opinion, the slight increase of lubrication during dissimilar wheel speeds and light clutch application more than outweighs the wear incurred without adequate additive.

      Matter of fact, I rebuild them and even my Traction loc behind a big FE will still chirp the tires in a slow corner until it breaks loose, and I rebuilt it in 1999. That's with two bottles of Mopar additive.

      My opinion is ALWAYS run it with clutch type limited slip diff and only run good stuff.

      My preference is

      1 - Mopar or Kendall in a small bottle
      2 - Ford

      I shy away from anything in a toothpaste tube
      70 Mustang - 489 cid FE, KC ported Edelbrock heads, Modified Victor Intake, Mass-flo EFI, Erson valvetrain, Supercomps, TKO-600, 4.10 9 inch.
      71 F-100 4x4 SB 4x4, 461 cid FE stroker, Edelbrock Pro-flo 4 EFI
      13 Ram Laramie 2500 4x4 6.7 diesel - trailer puller

    7. #7
      Join Date
      Nov 2006
      Posts
      456
      Your Ford Traction Lock has an organic friction material on the clutches and they wear much quicker than the steel clutches in the GM and Eaton units. I've rebuilt 40 year old Eaton units that didn't have enough wear on the clutches to require replacement. I've rebuilt many Ford units that had less than 100,000 miles on them and the clutches were so shot that there was no way they could lock up. The lubrication requirements for these different units are not the same. If a GM unit is working fine without the additive then it doesn't need it. For a drag racing application with little street use the additive should be left out completely. Only enough additive should be used to stop it from chattering when turning a corner. Most people just dump the whole 4 oz bottle in, and there is nothing wrong with that in a street car. The Kendall additive doesn't work well with the GM clutches. GM and Ford work fine.





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