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  • Rear diff issues

    well, i was sure i posted about the only pass (launch actually) that my car made this year. not me driving, due to shoulder surgery.

    back story; went to fire the car up, and seems like the T-stat held water and when it got cold it froze and shattered the block on cyl #2. FML. build whole new block, use all same hardware with new bearings/rods.

    dyno it with 10 less psi (38 instead of >47psi) and still pushed out 760 awhp ~580's wtq. GOOD!

    drop in an OEM B5 S4 trans, in fact the actual one i ran the first 9 second pass on. make ONE SINGLE LAunch. car goes to the wall, and parts on the track. we done.

    i built a motor for one launch this year. lighter side? saved a lot of money not running it this year.

    but, this is what i found today. i knew this was what had happened, but not to this extent. and no, the diff lock did NOT come undone this time.

    another shitter was my injectors got wasted over winter also. and to run this dyno and track day, my Honda buddy loaned me his 2000cc injectors and skipped a day at the track himself so we could do this. this one single show was the only planned runs for the car this year.

    fire it up for the first time.



    breaking in the motor on the fyno. give it a few light load passes and press it HARD.



    then go to the track with my alternate driver, and this, is what we get. this was a HARD launch should have been in the 1.3x range but he was out of it before the 60' lights.




    the things i do for this sport.

    But this is tonight's discovery. surprising thing is the first couple pictures is EXACTLY how it came down out of the car. that top piece just sitting there. what is amazing is that i drove it around the car show to park in the show area, then in the show promoters booth, then to the pits, and lastly into the trailer where we flushed the fuel and pulled the injectors for the owner who loaned them to me for the race.

    but i drove it all around and that piece of diff casing never fell off!












  • #2
    Yikes.

    So what exactly caused the diff casting to break? Something in the diff came loose and hammered the casing from the inside?

    BTW: At least one of those photos is going to get stolen and used in my Rear Diff Lock 101 post. Thanks for creating a "cut-away" drawing of the rear diff and rear diff lock control arm.

    RS2'd 93 UrS4 5 spd sedan
    94 UrS4 V8 6 spd manual avant

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    • #3
      HAHAHA!!! i can take more explicit pix if you so please. let me know EXACTLY what you want to see. and there is nothing stopping me from further dissection of this one.

      it looks as though a spider gear let go and got pushed out thru the top, to my untrained eyes. the spider gear pin is intact. the side gears are intact. its the two smallest gears that were destroyed.

      and that hole in the diff lock part? that corresponds to the bolt thru the outer case that holds it in place and acts as the upper half of the pivot point for the diff lock collar.

      and i prefer break away, as opposed to cut-away

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      • #4
        when i removed it, the locking side was locked to the input shaft, and the right side of the diff was turning freely as its gear was damaged the worst. that is the one that came thru the case. and even with no spider gears the input flange still turns the locker side of the diff, the left side output.

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        • #5
          Originally posted by speeding-g60 View Post
          HAHAHA!!! i can take more explicit pix if you so please. let me know EXACTLY what you want to see.

          and i prefer break away, as opposed to cut-away
          Yup, "break away" it is, no "cutting" involved.

          As for photos, anything that is nice a clear and crisp that would complement these diagrams (credit to you) from my rear diff lock 101 post (http://forums.quattroworld.com/s4s6/msgs/170940.phtml ) :



          RS2'd 93 UrS4 5 spd sedan
          94 UrS4 V8 6 spd manual avant

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          • #6
            Impressive

            As you have demonstrated the diff lock isn't the strongest design in the world as all the load of the right rear wheel goes though those two spider gears. Do you unlock the diff after launch or keep it locked throughout the 1/4 mile?
            91CQ20v - Gone to a new home
            93UR-S4 - The Magic Carpet
            94S2Bus - The Emerald Express

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            • #7
              100% locked all the time. driving, dyno, racing, parked.

              can kind of see the permanent bracket to keep it locked.

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              • #8
                Time to weld up the diff centre then?

                Spiders won't be getting out then....

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                • #9
                  ^ exactly what i was going to say, weld it solid and ditch the locking mechanism.
                  91CQ20v - Gone to a new home
                  93UR-S4 - The Magic Carpet
                  94S2Bus - The Emerald Express

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                  • #10
                    Wow, that is an impressive cross section.

                    You dont do anything by halves, including breaking stuff
                    Current-2004 Impreza PPP wagon

                    Sold-92 3B coupe-RS2+, 996s, konis, rear torsen, forged rods........
                    Sold ABY-stock

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                    • #11
                      impressive destruction there pal
                      Panthero Coupé quattro 20vt
                      Indigo ABY coupé
                      Imola B6 S4 Avant

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                      • #12
                        So will it be a Ford 9" or a spool for the Audi diff next? I know the new racecar is getting a Ford diff.
                        "Nulla tenaci invia est via"

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                        • #13
                          this is whats in the new car. narrowed Ford 9", all built by me (my first one!). back-strapped, four-linked, Strange double adjustable coilovers, wheelie bar mounts. lightened steel spool, 4.30 Pro-Gears with lightened ring gear. Strange aluminum third member with pinion brace, yoke keeper thing, forged yoke, and 40 spline rifle drilled flange lightened profile milled axles.





                          this is the car that my 3rd member came from, it was not the right gearing for his new setup. he had it as a backup. he did mention last weekend he should have kept it to run at SCSN the other weekend! he did recently win a Wally too, which is pretty cool.




                          and in all reality, it started with me taking this car to the chassis guy to talk about something different in the back and a back-half. but i couldnt find something readily available to use. the Audi 01E turns the output of the trans backwards from almost EVERYTHING else standard. i know an early Skyline R32/33 rear end has the same 4.11 and proper rotation.

                          but, at the time, i didnt want to take a year or more off from the car, like i ended up doing anyways. good thing though i did save a fair bit of money to put INTO the new car not having the costs of racing all year!

                          anyhow, here is some more rear diff stuff.
                          Last edited by speeding-g60; 27 November 2014, 03:01.

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                          • #14
                            Pix inside the lock portion.





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                            • #15
                              aaaaaan FINALLY the videos are done uploading! man the interwebz traffic last night was HORRIBLE!

                              made two vids as YT will probably kill the sound on the first one as the music was playing, i have had it happen before.

                              also keep in mind this is without spider gears present. if they were intact rolling one side would make the other side rotate in the opposite direction, until the lock was engaged then both sides would rotate the same direction.

                              i suppose if i were really bored i could take another one apart and put a good diff in this case to demonstrate that. i have a couple extra, as i now consider this a perishable item and therefore stock up on them when i see them




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