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T-56 in a 74 Avanti Part 1 - Clutch Hydraulics

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  • Clutch/Torque Converter: T-56 in a 74 Avanti Part 1 - Clutch Hydraulics

    My four speed dream has now grown by two to a six speed T-56 from a 96 Camaro.

    Why a six speed you ask! Well, I needed a clutch, flywheel and pressure plate anyway. I plan to put a lot of miles on the Avanti so I'd like to be able to optimize the rear end for performance and still travel on the open road under 2300 RPM's.

    And actually this trans had been setting on Craigslist locally for a long time with no offers, so I made one. It's brand new and in my pole barn now. It was purchased new from a local Chevy dealer about 10 yrs ago for use in an S-10 drag truck. After the original owner started to install it he decided to go TH400 and it set until lately. Looking inside, the innards show no sign of the gears meshing under power.

    [IMG][/IMG]

    Today was so nice in Michigan (50 deg) that I decided to try to install the clutch hydraulics to replace the old 4-speed mechanism.

    What to use was the first question? Junior (on the forum) had published an great post on using a Wilwood MC and a GM slave to operate his T-5 conversion using the original floor pedal. We exchanged a PM or two and I was ready to go that way, with the hanging pedal in the Avanti, until I started surfing the web and found several sites dealing with LT/LS T-56 conversions in earlier F-body Camaros. There was about every way imaginable to put them in but the over riding consensus seemed to be to use the OEM 94-97 hydraulics as it made matching the MC and slave cylinders easy.

    So I ordered the OEM setup and off we go.

    The hydraulics in the F-bodies use a 2" distance from the clutch pivot to the MC plunger mount so I used that number. The MC plunger travel distance is 15/16" and building that into the Avanti clutch pedal gives a little over 5:1 ratio and a travel of 5" at the pedal.

    I mocked the pedal to travel from 6" off the floor (total travel of the pedal originally is about 6 3/4" from the floor) to 1" off the floor. That should give me room for carpet and insulation and a stop for the pedal so I don't over extend the slave with to much travel from the MC.

    [IMG][/IMG]

    I then mocked up the clutch rod to give an angle that would clear the Brake MC and let the brake and clutch pedals swing clear of each other. I ended up with this configuration that keeps the clutch plunger travel almost in a straight line over 15/16" travel and clears the brake MC.

    [IMG][/IMG]


    That's the minimum clearance, I plan to build a shoulder bolt for the clutch rod attachment and that will give me about 3/8" of clearance between the pedals. The washers will be replaced with a bushing welded to the pedal. The washer stack is 3/4" so that will be the bushing length.

    [IMG][/IMG]

    Clearance below the Brake Booster.

    [IMG][/IMG]

    And without the booster.

    My plan is to build a bracket to support the clutch MC that fits under the brake booster mount and also bolts to the inner fender for more support.

    That will require more time than I have today so consider that a preview of coming attractions.

    One last data point, the 383 stroker needs a special flywheel to connect the two piece rear seal engine to the LT1 T-56. A Centerforce 700173 is on the way.


    One of the reasons for posting this early is to solicit opinions on what's been done and on further mods. After all, T-56 installs into Avanti's don't seem to be very prevalent on the forum nor web.

    Bob
    Last edited by sweetolbob; 12-16-2012, 11:42 AM.

  • #2
    You'll love the 6-speed.

    Wish I could help more with your Avanti install, but my T56 went into my '56 Hawk and used the underfloor master cylinder.

    Is your tranny a slave cylinder or hydraulic throwout bearing?

    jack vines
    PackardV8

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    • #3
      Originally posted by PackardV8 View Post
      You'll love the 6-speed.

      Wish I could help more with your Avanti install, but my T56 went into my '56 Hawk and used the underfloor master cylinder.

      Is your tranny a slave cylinder or hydraulic throwout bearing?

      jack vines
      Thanks Jack, I wish you could too.

      Short answer - Slave cylinder.

      More discussion -The LT to LS T-56's are kinda trade off's ville. The LT bolts to the older style blocks pre-98 and use the slave where as the LS bolts to the newer blocks and has a hydraulic TO.

      The LT is shorter overall due to a shorter bell housing that leaves no room for a hydraulic TO due to the "pull" disengage. Converting to an LS style that fits an older block requires a bell housing and input shaft change and results in a longer assembly overall.

      The one I have looks like it will put the shift lever in a useable spot which would be more difficult with the LS setup.

      The forums suggest that my LT setup will handle the output of the 383. I'd prefer the hydraulic TO but I like the other advantages of the LT.

      Bob

      Comment


      • #4
        Bob,

        Thanks for these updates. While I am glad you are the one who bought that car, my big regret is that you are geographically inconvenient to me. Probably advantageous for you as I'd be hanging around your place getting in the way but I can be usefull for holding the dumb end of the tape measure and supporting parts during mock up etc. Sometimes I even remember to bring cold beer...

        As I read your updates, I am learning immensely. Please continue to keep us in the loop as someday I will solve the empty spot problem in my garage.

        Merry Christmas and Happy New Years to all!

        Ken

        Comment


        • #5
          Originally posted by spokejr View Post
          Bob,

          Thanks for these updates. While I am glad you are the one who bought that car, my big regret is that you are geographically inconvenient to me. Probably advantageous for you as I'd be hanging around your place getting in the way but I can be usefull for holding the dumb end of the tape measure and supporting parts during mock up etc. Sometimes I even remember to bring cold beer...

          As I read your updates, I am learning immensely. Please continue to keep us in the loop as someday I will solve the empty spot problem in my garage.

          Merry Christmas and Happy New Years to all!

          Ken
          Ken

          Thanks for the kind words. Wish you were too. Nothing wrong with more help or another ear to bounce ideas off of. And if they bring beer, double good.

          Bob

          Comment


          • #6
            Hey Bob, was thinking about this the other day, and realized that the Avanti had hanging pedals...I was wondering if you were going to have room for the setup I came up with with the x-member from the convertible Lark frame...so then I thought...what was Bob thinking, he's got hanging pedals, not through the floor pedals! Anyways, report cards at school sucked up all my time, and I never got back to you, but the method you're doing it is exactly the way I would go too. Looks like you're going with the braided line too, smart move as that is how I discovered the Russell fitting I posted about last year...the Mickey Mouse plastic factory tubing does not like heat in confined spaces. Looking good, you're going to have so much fun with Avanti....just don't forget to get that '54 out for some execise too. Regards, Junior.
            sigpic
            1954 C5 Hamilton car.

            Comment


            • #7
              Junior

              During our discussions I was aware of the differences but needed advice on what was required on size and cylinder displacement as well as availability so your input was valuable. Interestingly, during my investigations, I found that the newer OEM units came with the braided line standard so I made sure that was what I purchased. Another advantage is they come assembled with fluid added so there will be no bleeding issues.

              The T-56 is a large tranny but it is setting on the pole barn floor close to a 700R4 that came out of my 83 Avanti. It's about as wide but slightly shorter so it should not interfere with the X-member. In any case, it'll fit I have a torc----- OOPS!!! A gallon of resin and a large supply of glass cloth and mat.

              While there is little info on these swaps into Studebakers, there is a tremendous amount of data on swapping them into older GM bodies so a lot of fitment issues have some clues available. The hydraulic system really cleans up the clutch setup in the Avanti's. Even if I had kept the 4-speed I would have gone with the hydraulics.

              In any case, your post was invaluable and adds to the knowledge base that the Stude community will need to draw upon as it moves into the future.

              Bob

              Comment


              • #8
                A former Avanti owner had an '82 or '83 Avanti he converted from an automatic to a 6-speed. I know a slave cylinder was installed in the installation. The only major modification I know of is that the console had to be opened up some for the shifter, but that was well covered by an aftermarket shifter boot. After several years he sold the car to someone in Florida.
                Poet...Mystic...Soldier of Fortune. As always...self-absorbed, adversarial, cocky and in general a malcontent.

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