M 21 yoke dimension (Joe?) - NCRS Discussion Boards

M 21 yoke dimension (Joe?)

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  • Dennis D.
    Extremely Frequent Poster
    • March 1, 2000
    • 1071

    M 21 yoke dimension (Joe?)

    Joe----

    I hope when you told me a yoke dimension you were checking from a part in your endless inventory.

    I purchased a new yoke that spec'd out in the joint fit and the shaft diameter. The shaft length was a little long, but when I had the trans out I was able to gently tap it until it bottomed out in the trans housing. Now I'm thinking problem solved.

    After putting everything back together, the last item was the driveshaft. I put the new yoke in, and tapped it all the into the trans to give myself plenty of clearance to attach the front of the driveshaft. Put on the rear joint and don't you know, the front still will not match up with the yoke. I even took off the caps off the joint. Still wouldn't go. That's with the yoke flush with the rear of the trans. I think there needs to be 1" or so of the yoke shaft showing. Has me puzzled.

    All connecting parts are in and line up. At the very least at the trans, all the brackets line up to the crossmember and the trans mounting points. The trans and extension are correct. The differential has never been touched and is located correctly.

    That leaves the distance from the trans output to the differential yoke as the only dimension that can be causing the problem. The driveshaft is the correct length, and the joints are also correct. Leaves the yoke as the one piece that I have no idea what the specs are, or even what it should look like.

    I linked a PIC of one from ebay to make it easier to understand my dimension question. I can bottom the shaft so that length doesn't matter. The only one left is the distance from where the shaft ends to the front surface where the "U" bolts install. The ebay piece is standing on the area I refer to. The piece I have measures 1 3/4" If you can verify this dimension I'd greatly appreciate it.
  • Joe L.
    Beyond Control Poster
    • February 1, 1988
    • 43193

    #2
    Re: M 21 yoke dimension (Joe?)

    Dennis-----

    The dimension I provided previously was an empirical (measured) dimension taken from a knowm-original GM #3868728 yoke, the same one originally used for your 1970 Corvette application. The dimension from the terminus of the tube section to the very end of the yoke (surface where u-bolts enter) is, nominally, 1-11/32". The combined dimensions, 3-5/8" + 1-11/32", make up the total length of the yoke (4-31/32", nominally).

    The yoke pictured in the eBay item is configured somewhat differently than the original GM yoke. However, providing that the critical dimensions are pretty much the same, it should work just fine. If the overall length exceeds 4-31/32" by any significant amount, it won't work.
    In Appreciation of John Hinckley

    Comment

    • Dennis D.
      Extremely Frequent Poster
      • March 1, 2000
      • 1071

      #3
      Re: M 21 yoke dimension (Joe?)

      Thanks Joe

      Your 1 11/32" and my 1 3/4" net what I think would be a significant 13/32". Can't seem to find a pic of an original. Your figures at least give me more info. Have a feeling there is more of a "cut out" up front where the joint would pass around. I'll keep looking.

      Comment

      • Dennis D.
        Extremely Frequent Poster
        • March 1, 2000
        • 1071

        #4
        Re: M 21 yoke dimension (Joe?)

        Joe

        Would you say this looks like the yoke I need

        Comment

        • Joe L.
          Beyond Control Poster
          • February 1, 1988
          • 43193

          #5
          Re: M 21 yoke dimension (Joe?)

          Dennis-----

          The configuration looks right. However, the seller says that this unit is for a 1963 with T-10. The 63 T-10 used a different spline configuration than the yoke used for 1963-70 Corvettes with Muncie transmissions. So, if this is, in fact, for a 1963 T-10, it won't work for your 1970 application.
          In Appreciation of John Hinckley

          Comment

          • Dennis D.
            Extremely Frequent Poster
            • March 1, 2000
            • 1071

            #6
            Re: M 21 yoke dimension (Joe?)

            Would the configuration be more than spline count? I was really interested in what this piece looks like from the inner end of the pipe to the bolt mount surface. This looks narrrower than the other ebay piece. Also seems "bowled out" more in the,(for like of a better word), saddle area where the joint sits.

            Trying to get a handle on this piece is like slowly pulling teeth. Fortunately, Your info is quickly getting me to the piece, and I certainly appreciate that.

            Comment

            • Joe L.
              Beyond Control Poster
              • February 1, 1988
              • 43193

              #7
              Re: M 21 yoke dimension (Joe?)

              Dennis-----

              The general configuration of the piece is pretty much identical to the Muncie yoke. As far as I know, the spline configuration is the only difference. I think that the T-10 piece is 10 spline whereas the Muncie is 26 spline.
              In Appreciation of John Hinckley

              Comment

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