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  • automatic transmission questions

    I am considering putting an automatic transmission in my racecar to solve some gearing issues. But I would like to control it manually. I do not know too much about this transmission (RE4R01A) but I understand it is shifted via the ECU which control shift solenoids. So I am wondering how difficult it would be to just use toggle switches to make the shifts? Or am I being overly simplistic? Major part of the problem is that I have no factory electronics left on the car, so it would be a bit of a job to back engineer everything to run the tranny.
    All I really need is neutral and second gear.

  • #2
    What exactly are you trying to do? Auto trans don't have a neutral, that's what the torque coverter does (decouple the engine from the trans input, or I should say allows slip when it's not locked up).
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
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    • #3
      I need to lower my overall gearing by around 12 per cent. Nismo did sell a gearset that would do it but even if I find it I will be looking at a pretty big bill. Whereas I can drop in an automatic with a low stall TC for a lot less money and second gear is right on the mark. Since I mostly race circle track, that gear would do the job for at least three of the tracks I drive at and we don't do a bunch of shifting. But I have stripped all the electronics out of my car and that transmission is fully electronic. Or is there an earlier non electronic version that would bolt up easily?

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      • #4
        Pretty certain you will HAVE to use the ecu to get it to work.

        Why not just run the ecu and wiring ?

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        • #5
          Yep, gotta run the ecu to control the valve body I'd say.

          Have you looked at D21 gearing and the other final drives?

          The auto will also weigh quite a bit more, and probably cost you quite a bit of power vs the manual.
          '18 Chevrolet Volt - Electric fun hatch for DD duty!


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

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          • #6
            After a little research, I have it figured out. You just need to toggle switch the solenoids in the correct order. The rock crawlers have been doing this for a while. I am not too worried about weight because I have to add over 200 pounds of lead to my car to make the weight anyway.

            These guys make a manual shifter for $100.00

            http://radesignsproducts.com/Rail.html

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            • #7
              I still dont see why you arent just using the transmission ecu, putting the shifter in 2nd, and calling it a day.

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              • #8
                Originally posted by Z28ricer View Post
                I still dont see why you arent just using the transmission ecu, putting the shifter in 2nd, and calling it a day.
                Because I am pretty sure that the transmission control unit is not stand alone is it? It would require inputs from the ECU to determine the shift points. Also I road race the car several times a year and it would be nice to manually control all the shifts.

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                • #9
                  I'd think the extra power loss would be more of an issue. What sort of speed range are you looking to get out of one gear?
                  '18 Chevrolet Volt - Electric fun hatch for DD duty!


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

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                  • #10
                    Originally posted by Def View Post
                    I'd think the extra power loss would be more of an issue. What sort of speed range are you looking to get out of one gear?
                    I am going to use a low stall speed torque converter and I don't expect I will see the power loss. One of the advantages to an auto is that even with the standard transmission and correctly geared I run out of revs because the gears are too short. So it works but I start below the torque curve and hit the corner well after the power has flattened out. And there is no time to shift. I think with 4 gears instead of 5 it will be better. At any rate it is a pretty cheap experiment so worth a try.

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                    • #11
                      Math is easy. What speed range are you trying to pull from apex to braking zone? What engine and tires? Fewer gears doesn't give them a greater speed range, just bigger gaps between gears.
                      '18 Chevrolet Volt - Electric fun hatch for DD duty!


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

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                      • #12
                        I have done the math and second gear is going to be perfect.

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                        • #13
                          Just trying to start some discussion. Have fun with the trans.
                          '18 Chevrolet Volt - Electric fun hatch for DD duty!


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

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                          • #14
                            Hey I appreciate all the input. I'll let you know how it turns out.

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                            • #15
                              So wait, right now you've got what a 4.08 stock rear gear, and a transmission with a 1.30 3rd gear.

                              5.3:1 in third

                              You want to go to an auto with a 1.54 2nd, with the same rear gear, for 6.28:1 ?

                              Getting an xterra 4.6 R&P just seems like a much smarter route.

                              As def already pointed out, rotating weight, static weight, and effort are all on the negative side for going with the auto, seems like you're trying awful hard to go the non logical route.

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