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Transmission Case Castings - SR vs KA

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  • Transmission Case Castings - SR vs KA

    Hi guys,

    I haven’t found any good info on this besides general listings for gear ratios for the FS5W71H, and the various videos and how-to’s for swapping an SR bellhousing onto a KA transmission. I am looking for info to identify KA vs SR “tail sections” by their casting numbers if possible.

    Consensus seems to be that KA and SR tail sections are identical, with the exception of 5th gear in some models. However I seem to spot different bearings (sealed vs non sealed), and different castings. Does anybody have good info?

    My baseline is an SR transmission that I’ve owned for ~10 years, and another that I bought today. Castings on the bellhousings match, however castings on the tail sections are slightly different, and upon closer inspection one has sealed bearings in the center plate (term may be incorrect) while the other has open bearings.

    Is it possible that one of these is a KA trans with an SR belhousing? I suppose the other possibility is that one of them had been serviced with different bearings. Both had been opened up in the past before I bought them. Does anybody have any feedback:

    Before / after initial cleanup:






    Matching bellhousing castings:






    Different tail section castings (#2 vs #1):






    Different center bearing types:






    A lot less wear on my “old gears” vs the trans that I bought today:




    Odd wear pattern inside the case + changed out shift fork?



    In Zipties We Trust....

  • #2
    I'm not sure about the casting marks, but I don't think they mean anything important. Sealed vs non-sealed is hard to call. Later model KA trannys had sealed bearings. I don't know if/when SR ever had open bearings.

    Have a look at this thread for more info. http://nissanroadracing.com/forum/ch...6322#post76322
    98 240SX SCCA STUish

    Comment


    • #3
      Thanks, some good info in Post #22 of that thread. Judging by the shift forks and the bearings that he showed in his pics, thinking the 2nd trans that I have is an early model S13 KA with an SR bellhousing. I haven’t disassembled the tail section to look at Reverse / 5th, so just judging based on the front section.

      Cheers,
      In Zipties We Trust....

      Comment


      • #4
        Hrm, judging by the tail section of this trans, I would agree that it has the “more complicated” shift linkage and a reverse gear which isn’t constant mesh. In other words, mine has the “blue” stuff which is visibly absent in the “red” circled bit of the SR trans.












        However, the shift forks in the front half appear to be a modified version that pairs a cast fork with an aluminum fork, with the linkage running completely through both, similar to the SR trans from his pic (circled “green”).

        Has anybody seen seemingly “modified” forks like this before?




        Can anybody confirm that their SR trans has a #2 casting like this one, or that their S13 KA has a #1 casting like this 2nd pic? I know that casting marks often mean nothing, but wondering if there is an off chance that they may correlate?



        ​​​​​​​

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        In Zipties We Trust....

        Comment


        • #5
          I'm think it was 94 Nissan changed to synchronized reverse I believe on all versions of the trans, even in the pickups. I don't see why the SR would be any different for that cutoff year. Meaning all older ones most likely have a reverse idler that engages when in reverse and later models have constant mesh with synchronizers. I do know the 89-90 KA trans is visibly different with far less ribbing in the casting than a 98 one, but I don't know if that translated to SR trans either.
          98 240SX SCCA STUish

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          • #6
            I’’d buy that explanation for synchronized reverse. Here are a few pics from the other side to more clearly show the gearing, rather than the shift linkages. On the casings, (beating a dead horse) I’’m just wondering if “pre-94” was #1 and “post-94” was #2.



            In Zipties We Trust....

            Comment


            • #7
              Just to help you beat it even more, I have 98 tailshaft with a #1 cast into it. I have 2 S13 KA trans one with #1 and one with #2. Don't know years though.
              98 240SX SCCA STUish

              Comment


              • #8
                Assuming the cases have never been swapped out / mix-matched, that kind of kills the theory then
                In Zipties We Trust....

                Comment


                • #9
                  S14 tailshaft housing has a different dust shield for the seal around the driveshaft since they don't have a guibo. Definitely an S14 housing
                  98 240SX SCCA STUish

                  Comment


                  • #10
                    turtl631 has my old S13 SR trans that as far as I know has never been opened (which is likely from the condition of the SR I pulled it from in early '04). Maybe he can chime in if he still has that thing... which honestly I'm shocked it held up to what it saw given the Zilvia reputation of the FS5W strength. 3rd gear would get very slightly grouchy on the occasional downshift on track, but otherwise it was driving like a champ when turtl631 took over ownership.
                    '18 Chevrolet Volt - Electric fun hatch for DD duty!


                    DefSport Koni Sleeve and Spring Perch Buy!!!
                    http://www.nissanroadracing.com/showthread.php?t=5902

                    Comment


                    • #11
                      The casting is #1.
                      ~1992 240SX, SR20/Koni track day car
                      ~2016 M3, daily driver

                      Comment


                      • #12
                        Originally posted by turtl631 View Post
                        The casting is #1.
                        Makes sense if it's a cutoff on early vs. late. The redtop it was from was an early 90's with no "cooling fins" on the front of the head.
                        '18 Chevrolet Volt - Electric fun hatch for DD duty!


                        DefSport Koni Sleeve and Spring Perch Buy!!!
                        http://www.nissanroadracing.com/showthread.php?t=5902

                        Comment

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