Stuck between 4r gears

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Stuck between 4r gears

Unread postby SlowBox » Wed Dec 05, 2018 11:29 am

Trying to locate the issues I'm having. Symptoms are jerking between 1 and 2 at the 1-2 shift under light throttle, and sometimes between 2-3 when I was playing with the tune. I also had issues on the 2-1 where the trans drags the motor down, almost like the TCC is applied a little bit.

Which function overrules the other? 1-2 or 2-1? Can they not overlap or something?

Tune will be posted later and the post edited.
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Re: Stuck between 4r gears

Unread postby decipha » Wed Dec 05, 2018 4:24 pm

no they cant overlap if they do u will get a rapid upshift downshift that will cause issues
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Re: Stuck between 4r gears

Unread postby 034v » Thu Dec 06, 2018 9:57 am

Frpm PRP:

TRANS_SHIFT_SCHEDULE_xy where xy is the shift. These are throttle position relative to closed throttle vs. what speed to shift at. You must make sure that the pair of shift curves does NOT cross. For example, you cannot have the 1-2 and 2-1 shift curves cross. If they do, the trans will most likely just shift back and forth at a fairly high frequency in the range that they cross and this is not good. It is recommended to graph the shift schedules when changing them to ensure they do not cross.

It is also recommended that you keep the existing shift schedule for that vehicle and just modify it. Making a whole new schedule is very difficult and probably won't work right no matter how good you think you are at tuning.

The same applies to the torque converter lock schedule; make sure they don't cross. The names for the shift and lock schedules are TRANS_CONVERTER_LOCK_x and TRANS_CONVERTER_UNLOCK_x, where x is the gear that that function is mapped to. At WOT; a locked up torque converter WILL transmit more torque to the wheels than an open converter, period. So, it is recommended to have the converter locked at WOT in all gears. Some of the older 5.0L Mustangs with AODEs had the torque converter locking at light throttle in 2nd gear to increase fuel economy. It is recommended to eliminate this to improve the drivability of the car. To eliminate this, just raise the MPH points so that they are very high at lower throttle positions and it will no longer lock. You can then step the curve down at heavy throttle positions so that it is allowed to lock up at WOT to improve power to the wheels.

To further improve the drivability of the vehicle, it is recommended to take the 3-4-shift schedule and paste it into the 3rd gear lock function, TRANS_CONVERTER_LOCK_3RD. This prevents the torque converter from locking in 3rd gear before the 3-4 shift and will generally improve the feel of the car when driving it.

At WOT, the trans shifts based of one of two things, whichever one happens first. Either the vehicle speed that is in the shift schedule functions or the WOT engine speed scalars, TRANS_WOT_SHIFT_RPM_xy, where xy is the shift that that scalar controls, like 1-2. What this means, in most cases, is that this is where the shift is COMMANDED and not where it will occur. In some transmissions it can take up to one second to fill the on coming clutch. If the engine is accelerating at 1000 RPM per second (not unusual for 1st gear with a 3.73 axle ratio) that means that from the commanded of the shift to the actual shift point, the RPM will increase by 1000 rpm. So, if you set the TRANS_WOT_SHIFT_RPM_12 to 5000 rpm, the shift will occur around 6000 rpm. This is important to know when setting up WOT shift points.
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