Like I said, the shift points in the TCM tune are a goal for where the WOT shifts are supposed to happen. If the truck with 350hp come up at 400rpm per second and the trans learns how to "time" the shifts to get them to happen at 3250, then you tune the truck to 500hp and it comes up at 500rpm per second you just threw off the TCM's "timing" on the shifts. The command for the shift starts at the same time as it was before but since the RPM is coming up faster it gets to a higher RPM before the shift actually occurs. Think of a batter that always plays against guys that throw 80mph fast balls, he gets in front of a guy that throws 100mph and he is gonna swing late. Get it now?
On top of that as Shane said if you ECm tuning was done to fix your speedometer for tire size it can throw off the shifts.
ok that makes perfect sense but one of the main reasons i was confused is even though i made the switch to EFI im still running the same power level as previously with my stacked setup....but i do totally see what you are saying
Also consider that with less defuel the computer keeps fueling through the shift and as a result takes the trans longer to make said shift and will contribute to blowing past shift points , dustins first post is spot on how i make changes as well , on my truck i blow past commanded shifts by 600 rpm before the converter locks then it is pretty spot on , your stock converter isnt helping either .
this also makes perfect sense and another thing i didnt think of. thanks Trent.
however with this tune since Nick is aware that im "going for broke" on the stock trans i would assume that the defueling is stock or very close to stock. but then again im no expert (Yet
) so thats just an assumption haha
In the ECM tune you can disable some rev limiter stuff. I did it once and my shifts were about 200 RPM higher than they usually were, close to 3400.
Doesn't make much sense seeing that the TCM should still shift under the same parameters but it definitely did make a difference. I never looked into it too much because I thought it was garbage. All it did was shift super hard and throw a low rail pressure code along with a P0700. I roll with stock TCM tuning.
This i think is the exact answer to why my shift are different now (along with the other answers as well) becuase you see my Banks/superchip setup had no provision for the rev limiter so therefore it was stock. so no matter what it HAD to shift at 3200 and now that the rev limiter has been raised to 4100 it allowed the the things othrlgrl and trent were talking about to occur.
the only thing that has me slightly baffled is the 4-5 shift which is exactly the same as before....but oh well im sure ill be playing with the TCM tune to correct it soon. i just thought that nick left the 4-5 shift alone becuase the plan as of now if to lock out 5th and try to get down the 1/4 staying in 4th.
but i think im gonna change that so i dont lock 5th out but rather delay that shift as long as possible.
Thanks guys
