2012 GT mustang tire bark then slip when shifting 1st to 2nd lost traction

[elerico]

2012 GT mustang tire bark then slip when shifting 1st to 2nd and i lost traction and rpm drop

2nd to 3rd is perfect.

car shift around 7200, and bang, the rear slip when shift occur and i lost a lot of time during the shift because the rpm drop so bad

Torque Reduction / Master enabled switch is disabled
Torque Reduction / Shift enabled switch is disabled

should i reanable one or both switch and max out the other table and leave alone the 1-2 shift table ?

i log 574lbs in scheduled torque when the shift happen

thanks !

[murfie]

Just to be clear your goal is to make the 1-2 shift softer but not slower?

Can you post a log that has at least the throttle position(voltage), desired brake torque, engine brake torque, engine RPM, transmission temperature, input shaft speed, output shaft speed, all element pressures, TCC pressure, TCC slip, and TCC desired slip?

The 1-2 shift above 4MPH(1A-2M) is a challenge to not shock the tires as the TCC is open, no boost pressure is applied to an off going element, and you only have an oncoming element(C) ramp rate to work with. (Easier to notice in the 2015+ autos) As gear shifts get higher you see torque transfer times increase and overall slip decreases. This is because the TCC starts to apply minimizing input slip for fuel efficiency, but torque needs to be applied slower for smoother shifts. The 1-2 shift at WOT the TCC is not applied, but applying the same method to the 1-2 shift should minimize wheel shock by slowing applied torque while keeping the shift quick by decreasing slip. Initial slip would be how quickly the clutch pedal is depressed,overall slip would be how quickly you changed gears, and torque transfer would be like how fast you release your clutch in a manual. Telling it to slip longer than to transfer torque is a rougher shift just as shifting slower than releasing the clutch is in a manual, minus the chance of grinding a gear, just slipping one badly.

If your 1-2 table is stock and has 5000ms I would try starting with 700ms and seeing if that helps the tire shock. 5000ms means its pressure dependent which can engage the element transferring the torque fast even at a 5 psi/s ramp rate.

[dbb2797]

Kind of inline with the OP's question, but maybe a little different. Murfie, what would you recommend to get the quickest possible shift in terms of not having a drastic RPM drop during the shift? I don't care about firm shifts. They can have no firmness and I'm good with that. But what I was noticing today during my testing of a new gear ratio (went from 4.10 to 3.25) was that I'm getting a significant RPM drop during my shift. 1-2 I dropped 1900 RPMs and 2-3 I dropped 2400 RPM's.

I'd like to get as little RPM drop as possible with the as quick as possible of a shift.

[murfie]

With a rear gear change like that, larger RPM drops are to be expected. To minimize RPM drop I would start at working toward unlocking the TCC and having it ramp on slower. if that doesnt help enough you would need to play with lowering the oncoming pressures in the input shaft RPM range you are seeing to see if you can introduce some slip in the transmission gear clutch's. There's only so much you can do before you cause excessive wear and changing the rear gear back would be more beneficial.

[dbb2797]

Thanks Murfie. The reason I went to a 3.25 gear is because I have the cobra jet manifold and this gear allows me to stay in the 6000 - 7600 RPM range longer. And on the 1/4 mile, I can stay in third gear and don't need an additional shift. Since I bracket race the car, I can accept a larger RPM drop as long as it's consistent. Currently I have the converter locking up a little bit after shifting to 2nd gear. I think I'm going to just keep it open though. The car is consistent once it gets shifted into 2nd gear and the converter has finished locking. I notice a small RPM dip too when the converter locks. So I'm going to experiment with just keeping it open and lowering the oncoming pressures.

[elerico]

Just to be clear your goal is to make the 1-2 shift softer but not slower?

C.

YES !
but its only occur on street tire
NEVER on drag radial

so maybe the trouble is in my head