Shift point WAY OFF after shift kit+converter

[lance_mn]

The Car:
95 LT1 Z28, 4L60e
I've adjusted my shift points multiple times and it has always worked very well. The actual shift comes ~200RPM later than what I program, but that delay is expected and consistent: setting to 5800 brings a shift right around 6000, setting to 6300 brings a shift right around 6500, etc etc.

The New Parts:
I just installed the following in the tranny:



2400 stalled torque converter
Servo from a Corvette
Shift Kit (RatioTek)


The Problem:
The car now shifts at 7k rpm.



Was there something I was supposed to change in the ECU after installing a shift kit to keep it shifting properly?
Is there such thing as a shift kit which not only hardens shifts, but actually delays the shift point them as well?

[lance_mn]

To be clear, I put this under "tunerpro talk" because I'm wondering specifically if there is something I'm supposed to do in tunerpro to correct for the mechanical changes.

[lionelhutz]

That's an odd one. A shift kit should "speed up" the shift. But then, the new higher stall converter will likely "slow down" the shift. I use quotes because I'm referring to commanded vs actual shift rpm. At any rate, you probably do have to adjust the PCM since you did change the combination you're running and that causes it to both drive differently and react to shift commands differently.

Have you tried dropping the shift rpm and mph a bunch to see when it does shift or if it will shift? Test something like 4000 rpm and 0 mph. The mph could be biting you now because the new converter might be causing a lower mph at your shift rpm. First thing you've got to do is ensure you can control the shift points. The builder screwed something up that he needs to fix if you can't.

You shouldn't be hitting the stall wall - basically at launch you get a code and then it hits rev limiter and shifts 1-3. That should only happen on a 3000+ rpm stall. No codes, right?

[lance_mn]

FIRST AND FOREMOST THANK YOU for taking the time to help, man! Seriously.

I should point out that the 7k shift was happening in the 1->2 shift only, and 2->3 was happening around 6.5k.

I eventually decided to just try again... after only 1 more hard pull, it started shifting at 6.5k in 1->2 as well, without any tuning. It's as if the ECU needed to learn something about the new transmission parts....


So anyhow, then I had it shifting at 6.5k constantly in all gears.



Have you tried dropping the shift rpm and mph a bunch to see when it does shift or if it will shift?


Just now I set all shift points to 5000 RPM (MPH are all so low that they're not relevant at all).


RESULT:
- 1->2 happens at ~6k exactly
- 2->3 happens at 6.5k. completely unaffected by my tuning change.


To be clear, the 2->3 shift is programmed for 5k and doesn't happen until 6.5k :yikes: Is this typical? Do you guys mod your trannies and then have a 1k+ disparity between your shift point setting and ACTUAL shift?


I have only come up with one idea. Check out my "Shift Time vs TPS vs Shift":

14284



My theory: The 0.75 setting allows the tranny to apply more pressure and get the 1->2 shift to happen when it takes too long. Meanwhile, the 6.38 second setting for 2->3 means the tranny waits too long to start applying extra pressure.

However, I don't feel confident enough in my own knowledge to change these fields, and furthermore if this was it, then there should be a much bigger difference between 1->2 and 2->3.


The mph could be biting you now because the new converter might be causing a lower mph at your shift rpm That's a good point. I lowered the MPH even more than they were to ensure they are well and truly out of the way.


First thing you've got to do is ensure you can control the shift points. The builder screwed something up that he needs to fix if you can't.
This is my worst fear. If he did screw something up, I have no way of proving it, and have absolutely no interest in taking this tranny out again ughh.



You shouldn't be hitting the stall wall - basically at launch you get a code and then it hits rev limiter and shifts 1-3. That should only happen on a 3000+ rpm stall. No codes, right?

No codes and it's definitely not going 1->3. thanks for checking though man, I had no idea about that.

[LeMarky Dissod]

I have only come up with one idea. Check out my "Shift Time vs TPS vs Shift":
14284
My theory: The 0.75 setting allows the tranny to apply more pressure and get the 1->2 shift to happen when it takes too long. Meanwhile, the 6.38 second setting for 2->3 means the tranny waits too long to start applying extra pressure.

However, I don't feel confident enough in my own knowledge to change these fields, and furthermore if this was it, then there should be a much bigger difference between 1->2 and 2->3.Your idea is correct. In the 'Shift Time Vs %TPS Vs Shift, Norm, Low Alt' & 'Shift Time Vs %TPS Vs Shift, Norm, High Alt' tables, NONE of the shift times need ever exceed 0.8 secs (800msec).

(Note that the 'Performance Mode' versions of those tables have shift times of 0.000 specified.)


I lowered the MPH even more than they were to ensure they are well and truly out of the way.Shifting by engine RpM is far more accurate and safe. Still, the shift MpH[s] should not be too far under the RpM.

As an example:
my WOT 1up2 MpH is set @ 36MpH [which corresponds to 4875RpM]
my WOT 1up2 RpM is set @ 5250RpM [which corresponds to 39MpH].

In other words, just far enough apart that I can tell if something goes wrong between the Opti- & the pcm, but not so far off that it feels like a valet mode / parent mode.

Anyway, if that doesn't help make things more consistent, you need to check the rest of the line pressures.

[lionelhutz]

Definitely lower those times and see what happens.

Basically, the PCM adjusts the line pressure so the shift takes the time in that table. It's called adaptive line pressure or something like that. The idea is to keep the transmission shifting the same throughout it's life as it wears.