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Thread: Jeep 42RLE question...

  1. #1
    Tuner in Training
    Join Date
    Sep 2019
    Posts
    14

    Jeep 42RLE question...

    Can someone please explain to me why does raising the RPM on the 4-3 downshift initiate the shift sooner with a lower throttle position? It seems that logically you would lower the RPM but that's not the case. What am I not understanding here? 😁

  2. #2
    Advanced Tuner
    Join Date
    Jan 2018
    Posts
    703
    It?s the threshold at which downshift occurs. If you raise the rpms at which downshift occurs the sooner it will hit that threshold to command downshift. The rpm doesn?t go to zero when you coast and count upwards towards the rpm target, it goes down from whatever it is at when you let off the throttle towards the threshold. Or, if you raise rpm to a point where you give it more throttle and your actual rpm is below the threshold of the new throttle position it will command a downshift. And of course rpms is output shaft speed.

  3. #3
    Tuner in Training
    Join Date
    Sep 2019
    Posts
    14
    Got it now, thanks. I made an Excel spreadsheet that converts the output shaft RPMs to engine RPMs for each transmission gear ratio. Now I can better visualize what the changes will do before I make them.