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  • 8.8 diff install

    hi guys.. putting a 8.8 diff into 1960 tbird,, because of the offset of leaf springs is their any percautions I need to know ? ie spring perches offset/pinion angle pre set when welding new perches.. hope this makes sense .... do I square off the raer end and go?? any heads up is appreciated... thanks
    Tom
    Tom Splane

  • #2
    Originally posted by TOM1960SQUAREBIRD View Post
    ...because of the offset of leaf springs is their any percautions I need to know ?..
    Most of the 8.8" rear ends I've met are set up for coil springs. I don't know what yours came out of but the swap is pretty straight forward.

    When you relocate your perches there will be no offset. Simply maintain the same axle angle as your trans tail-shaft. - Dave
    My latest project:
    CLICK HERE to see my custom hydraulic roller 390 FE build.

    "We've got to pause and ask ourselves: How much clean air do we need?"
    --Lee Iacocca

    From: Royal Oak, Michigan

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    • #3
      Originally posted by simplyconnected View Post
      Most of the 8.8" rear ends I've met are set up for coil springs. I don't know what yours came out of but the swap is pretty straight forward.

      When you relocate your perches there will be no offset. Simply maintain the same axle angle as your trans tail-shaft. - Dave
      Maybe he is doing an 8.8 out of an explorer that is an old school iron straight axle?

      I have a few Mustang Cobra 8.8s laying around, I have thought about swapping the whole cradle into my TBird, but that's as far as I've got.... thought about it...

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      • #4
        No doubt Bryan, the 8.8 was used in many lines of cars and trucks. I've only had cars so I'm limited.

        SN95 T-birds and Mustangs were graced with 8.8 rear ends, very successfully. The Cobra cradle was an independent suspension version that was cleverly done. I never thought about retrofitting it to a Squarebird but hey, why not? They even have disk brakes in the assembly!
        My latest project:
        CLICK HERE to see my custom hydraulic roller 390 FE build.

        "We've got to pause and ask ourselves: How much clean air do we need?"
        --Lee Iacocca

        From: Royal Oak, Michigan

        Comment


        • #5
          Just a note: If you are changing to the 8.8 due to a belief that it may be a "better" engineered unit, it's not!

          Scott.

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          • #6
            Originally posted by simplyconnected View Post
            No doubt Bryan, the 8.8 was used in many lines of cars and trucks. I've only had cars so I'm limited.

            SN95 T-birds and Mustangs were graced with 8.8 rear ends, very successfully. The Cobra cradle was an independent suspension version that was cleverly done. I never thought about retrofitting it to a Squarebird but hey, why not? They even have disk brakes in the assembly!
            Yes, the Cobra rear end cradles I have are complete units, have disc brakes, anti roll bars, shocks, the whole thing. With a limited slip geared at 3.56...

            I'd post a photo.... but to much effort anymore

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            • #7
              One thing I would not do is set the diff angle exactly the same as a 9. The nine has one of the lowest pinions on the planet. Probably at least some change in driveshaft angle, vs diff angle between the two.
              59-430-HT

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              • #8
                Originally posted by OX1 View Post
                The nine has one of the lowest pinions on the planet.
                And due to such, is where much of the greater strength within the ring & pinion relationship vs. say, the 8.8 resides.

                Scott.

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                • #9
                  Originally posted by pbf777 View Post
                  And due to such, is where much of the greater strength within the ring & pinion relationship vs. say, the 8.8 resides.

                  Scott.
                  No doubt. Unfortunately, the stock 9" cases were weak in the 3rd pinion bearing area and that little chunk liked to crack off and test the strength of the rest of it.

                  Had a whole bunch of them on all my 78/79 broncos, think I broke every one of them in some fashion before moving to a D60, then 14 bolt, and then Unimog axles finally.

                  http://i.imgur.com/OZnj8.jpg
                  59-430-HT

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                  • #10
                    That's a nasty gear. Are these Ford gears?
                    Attached Files
                    My latest project:
                    CLICK HERE to see my custom hydraulic roller 390 FE build.

                    "We've got to pause and ask ourselves: How much clean air do we need?"
                    --Lee Iacocca

                    From: Royal Oak, Michigan

                    Comment


                    • #11
                      The failure of the 9 inch case casting at the pinion pocket/pilot bearing is actually caused by a failure in the responsibility of the bearing set higher on the main pinion shaft located within the pinion support assembly. It is paramount that these two bearings remain preloaded so as to provide the support and maintain shaft alignment and pinion head relationship to ring/crown gear. The pinion pilot bearing was intended only to support and dampen flex imparted from the base of the inner/bottom pinion bearing at the back of the pinion head thereby causing deflexion in the relationship of the contact surfaces of the ring & pinion.

                      Under the load or drive direction the pinion is attempting to move upward and away from the ring gear and is crowding the case casting on the solid side as intended for high load instances. Under coast or decel the ring gear pulls the pinion head inward and downward toward the strap or weak side of the casting. So, often when one experiences this type of failure, with further inspection you will find that the preload on the pinion bearings within the pinion support was lost, hence the failure of the case at the pilot bearing because it was being overworked beyond the original intentions.

                      Ford addressed increasing the stamina of the 9 inch with the introduction of the "Daytona" pinion support back about 1964 +/-. This component introduced a larger bearing at the pinion head (front or outer bearing remained the same) and a solid vs. the "crush ring" to provide better support and reduce the "shaking" of the pinion gear particularly when rolling on & off the throttle under high loads (as at Daytona).

                      In the other units described, including the 8.8, which do not have the pilot bearing features, of coarse they don't suffer from this failure, but the pinion head is just allowed to move without the resistance provided in the 9 inch's third bearing, causing excessive ware or damage to the gear set. Hence another reason the 9 inch is better!

                      Now we must keep in mind that any device has its' limitations. The Ford 9 inch was designed for car and light truck (1/4 & 1/2 ton) applications, which it is superior to any other in this range of application. The Dana 60 and the 14 bolt GM "Corporate" was designed for the 3/4 to 1 ton applications (yeh, I know, Dana 60 was also available w/ Chrysler "Super Track Pack" option) therefor it is of greater capacity, when comparing all in stock form.

                      Unfortunately, the latter, do to pinion gear placement in relation to ring gear, do not permit sufficient pinion dimension to compete with the 9 inch in the numerically higher ratios popular in racing, hence the overwhelming dominance of the 9 inch. in such.

                      And yes, as the 4 X 4 tires get bigger, so must the diffs., Unimog & 2-1/2 ton Timkin/Rockwell military, then to 5 ton military, and finally on to units with planetary hubs.
                      Scott.
                      Last edited by pbf777; April 13th, 2018, 08:20 AM.

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