No Full Throttle 1-2 Shift

[sy34010]

On the street and even sometimes on the track I hit the rev limiter (7400) before I make the 1-2 shift which is set at 6700, once that happens the shift won't happen until a back off on the throttle. This also happens when I kick down from 2-1 anywhere below 45 MPH. Should I try a lower shift point, the wheels always spin with street tires on and it seems like the engine revs so fast that the trans doesn’t have time to react hence no shift. Or do I just need to resign myself to the fact that I need to keep my foot out of it below 45 MPH unless I’m at the track with the slicks on?



94 Impala SS SS, F1 Procharged 409 (408.6) LQ9 15.5 PSI 670 to the wheels

[NOS500]

Try lowering the shift speed not rpm at WOT in the 1-2 shift

[JasonB]

post the tune.

[sy34010]

Here it is but you may not be able to open it I'm using the latest beta

[JasonB]

can't open it.

[Cantalope Kid]

Lower your trans. shift time to .100 across the board, and yes lower the shift RPM. You'll be surprised at what it actually will shift at despite you lowering it. I have a friends at 6350 and we kept hitting the rev limit at 6500rpm. We lowered to 6250 and the damn thing will actually hold to 6425rpm before finally completing shift. Lower yours in increments until you get it where it should be...

[sy34010]

Thanks for the ideas, I'll work on it tomorrow and weather permitting at the track on Saturday.

[Bill@HPTuners]

Try logging trans output shaft rpm so you can calculate the trans mph which is used by the pcm to calculate the wot shift points.

(60*Trans output shaft rpm)/trans output revs/mile(which is found in your editor file) is the calculation.

For instance if your 2-3 wot shift mph is set for say 50mph and your transmission is getting a calculated mph of 48mph whereas the vehicle mph is 65mph the vehicle will not even attempt to shift until it reaches the transmissions calculated mph. I've seen it happen a few times and the easiest way to check things out are by double checking via a spreadsheet to make sure things are calculating correctly on both ends so you can at least rule that out as a factor.

[sy34010]

I think we'll call this tune good, I lowered the 1-2 shift MPH to 20 and the RPM to 6200 and found the sweet spot, at least on slicks. Ran 10.80 @ 130 while spinning out of the hole and wiggling just before the 2-3 shift.