THM for a Mid-year??? - NCRS Discussion Boards

THM for a Mid-year???

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  • Bill L.
    Expired
    • March 31, 1985
    • 349
    #1

    THM for a Mid-year???

    HI all....

    Hope everyone is doing well.....

    A client asked me about changing out a 1965 Power-Glide equipped automatic to a 68 series THM....

    Does anyone have some specific experience in this regard?? Opinoins welcome as well ...The power glides are fine but.....

    Let me know your thoughts...

    Regards
    Bill
    Tags: 65-pg-to-68-thm
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    • Richard G.
      Extremely Frequent Poster
      • July 31, 1984
      • 1715
      #2
      Re: THM for a Mid-year???

      The 350THM will fit. The 400THM will not.
      I am assuming you meant the 1968-400THM as the first 350 wasn't built till 1969.
      The short story is although GM had made the 400 since 1964 it didn't fit in a C2.
      More room, in the tunnel, for the 400THM was one of the changes incorporated in the 1968 model year.
      If I has going to change the transmission out I would consider the 2004R if it's not behind a lot of power.
      Takes the same driveline length as the PG. And you get an overdrive to boot without computer controls.
      Of course you get a first gear with the 350. (Second in the 350 is close to the PG first) Either transmission is a win in my book.
      Rick
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        • James W.
          Extremely Frequent Poster
          • November 30, 1990
          • 2640
          #3
          Re: THM for a Mid-year???

          The 2004R with the lock-up overdrive would be my choice. Back in the mid 1990's, my '87 Buick Grand National which was factory equipped with this transmission was making over 400 hp at the wheels and would run mid 11 second quarter miles. All I did was install a shift kit, otherwise all stock. If you can find one out of a 1986 or 1987 Monte Carlo SS that will work. Others GM car brands with this transmission should work also. If you could fine one out of a GN that would be ideal, but they are scarce.

          Just my 2 cents.

          James
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            • Richard G.
              Extremely Frequent Poster
              • July 31, 1984
              • 1715
              #4
              Re: THM for a Mid-year???

              The 2004R also has what is know as a corporate case. One out of a Buick will fit the 327. They all fit a SBC.
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                • Mark E.
                  Extremely Frequent Poster
                  • March 31, 1993
                  • 4496
                  #5
                  Re: THM for a Mid-year???

                  I've never done it, but Google can help you find kits for the 2004R that include TV cable & bracket, dipstick, cooling lines, converter, etc. It's not clear if they offer mounts specifically for Corvette and how they handle the shift linkage. You'll have some driveshaft work too. Is the back up light switch on these cars on the tranny?

                  You'll also find GM 4L60E kits that include the electronics, if you want to go that route.
                  Mark Edmondson
                  Dallas, Texas
                  Texas Chapter
                  1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
                  1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top
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                    • Richard G.
                      Extremely Frequent Poster
                      • July 31, 1984
                      • 1715
                      #6
                      Re: THM for a Mid-year???

                      The 200R4 is the same length as a Muncie,PG and the THM350. No drive shaft work required for this group.
                      A change to the 700R4/4L60 will require a drive shaft length change and a some type of adaption work on the mount.
                      With the frame/cross-member on a C2 the change to a 700R4/4L60 will be significantly more work.
                      It's been done but with so many easier options I am not sure I would recommend it.
                      Why we love our Chevys.
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                        • Bill L.
                          Expired
                          • March 31, 1985
                          • 349
                          #7
                          Re: THM for a Mid-year???

                          Rich, Mark & James....

                          Thanks guys... this is some good info.... I am usually a "bone-stock" kinda guy but the client wants this....

                          Thanks Again!!!

                          Regards
                          Bill
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