4L60E wont shit WOT when commanded

[Lahmer_52]

Im having issues with my 2-3 shift all the sudden. I was at the track last weekend and the car would not go into third until I let off. I checked shift schedule for speed and RPM and all aligned with where I wanted to shift. In the attached tune file that I loaded today I set the 2-3 shift at 6,000 RPM but it did not command 3rd gear until after 6,600 and actually execute it until a few hundred RPM after that. You can see in the log file at about 3.52 where I did the WOT pull. What am I missing with this tune that it doesn't want to shift? Motor is a HCI LS1, trans is a performabuild lvl 2 with yank 3600 stall converter. Ive never had this issue before so curious what got messed up to cause this.

Thanks for the help,
Blake

[IndyPete]

Im having issues with my 2-3 shift all the sudden. I was at the track last weekend and the car would not go into third until I let off. I checked shift schedule for speed and RPM and all aligned with where I wanted to shift. In the attached tune file that I loaded today I set the 2-3 shift at 6,000 RPM but it did not command 3rd gear until after 6,600 and actually execute it until a few hundred RPM after that. You can see in the log file at about 3.52 where I did the WOT pull. What am I missing with this tune that it doesn't want to shift? Motor is a HCI LS1, trans is a performabuild lvl 2 with yank 3600 stall converter. Ive never had this issue before so curious what got messed up to cause this.

Thanks for the help,
Blake

Well, my passengers always shit when I go WOT but as far as tuning the shiftpoints, there is always a delay from the time it commands a shift until it actually completes it. Log current gear and see when the current shift takes effect. Look at the log and see what speed/rpm that is and what the difference is for the full shift to be completed and subtract for the correct final rpm/speed.

Lets say it takes half a sec to complete a shift. If you want it to shift at 6600 rpm you need to go half a sec back in the log and type in the speed/rpm you see there. You may need to start it at 5900 depending on how fast you gain rpms (what gear you're in etc)


Pete

[Lahmer_52]

Today I trialed lowering the Full Throttle shift speed well below where the actual shift takes place. I set the speed to 60 mph even through at 6,000 RPM the shift should take place at around 70 mph. I did a test run and the ECM finally commanded the 2-3 shift at around 6,000 rpm at 74 mph. Could something be messed up with the speedo settings the ECM uses to calculate how fast the car is going? Speedometer is accurate, but having a hard time understanding why I have to falsify that MPH shift speed so much to let it command the shift at the correct RPM.

[IndyPete]

Today I trialed lowering the Full Throttle shift speed well below where the actual shift takes place. I set the speed to 60 mph even through at 6,000 RPM the shift should take place at around 70 mph. I did a test run and the ECM finally commanded the 2-3 shift at around 6,000 rpm at 74 mph. Could something be messed up with the speedo settings the ECM uses to calculate how fast the car is going? Speedometer is accurate, but having a hard time understanding why I have to falsify that MPH shift speed so much to let it command the shift at the correct RPM.

Well. You need to log rpm, speed, and current gear to dial that in. The delays will always be there. Below is an example of my 6th gen Camaro SS and where it commands the gear shift vs the actual gear shift. If I wanted to raise my rpm shiftpoint by 200 rpm for instance Id have to tap the right key, Look at the 5200 RPM (200 higher than the 5000 that it shifts at currently) and look at the corresponding speed, which is 30.70 MPH. This is the method you need to dial in your shifts.

As a general rule, shift scheduling, part throttle shift (100% pedal column) , full throttle shift speed and full throttle shift RPM should match. Look at the data in the two attached examples to help visualize.


shift 1.PNG
shift 2.PNG

Pete

[Lahmer_52]

I did something very similar to the images you have set up and they are a very close mirror image. When the ECM commands the shift there is a 100-200 RPM lag from when the actual shift occurs. That part looks good, im just curious why i have to cheap my full throttle shift speed down so much to get it to command at the correct RPM. Right now the tune has 60 MPH loaded but actual shift is at 74 mph. If i load a value closer to 70 mph it will not command the shift until i let off the gas. Does the ECM use the speedometer or is it making its own calculation on speed based off the VSS sensor? I did not do the original tune on the car so curious if someone messed with that calibration and now the trans is calculating the wrong MPH.

Thanks for all that advice!
Blake

[IndyPete]

I did something very similar to the images you have set up and they are a very close mirror image. When the ECM commands the shift there is a 100-200 RPM lag from when the actual shift occurs. That part looks good, im just curious why i have to cheap my full throttle shift speed down so much to get it to command at the correct RPM. Right now the tune has 60 MPH loaded but actual shift is at 74 mph. If i load a value closer to 70 mph it will not command the shift until i let off the gas. Does the ECM use the speedometer or is it making its own calculation on speed based off the VSS sensor? I did not do the original tune on the car so curious if someone messed with that calibration and now the trans is calculating the wrong MPH.

Thanks for all that advice!
Blake

I'm fuzzy on the logic, I'm guessing its some sort of OR or AND thing logically that has to happen. Good thing though, if you set all 3 tables to match you don't have to worry about the logic behind it :-)

I just got some time to look at your tune and what it shows in the original you posted it commands shift 1-2 at 34 mph, the log shows the corresponding RPM is 5300 and its set at 6700 in the tune. So Id set the RPM at 5300 for that shift to match. On your 2-3 shift it gets a little off. Your part throttle table commands that shift at 70, the WOT at 68 and the RPM at 6000. The 0.7 secs delay (from 6000 rpm) is not all that crazy (It is after all a 4L60E). I'd dial it back 500 rpm and make it 5500 RPM and 65 MPH, and change the part throttle speed 100% to that as well. See where that lands and adjust up accordingly. Your 3-4 shift is out of sync the most, the part throttle tables shows shift at 115 MPH, The WOT shift speed shows 90.66 and your RPM shows 6600. Make all the speeds and rpms match what the log says and then datalog again, then tweak to perfection going up so you wont hit rev limiters. As far as the tranny tune... You could do some stuff to shorten the delays a bit with pressures etc but I don't have enough experience with the 4L60E to help you there. I tend to stay away from tuning them much since they have a tendency to blow up if you look at them the wrong way. If I didn't have strong feelings about the tranny I'd maybe raise the shift pressures 20 - 30 psi or so, play with torque management etc. See how that behaves.

Good luck!

[Russ K]

That tune shows that the calculated tire dia is only 21.99", not 26.4". That's why the shift speeds are 20% higher than your shift speed tables.

So enter 2,849.94 in the trans revs/mile.

Russ Kemp

[Lahmer_52]

Awesome, I think that was the variable I was missing. I think whoever tuned this car before me messed with VSS pulses/mile and Trans revs/mile, is there a calculation to get those corrected and make sure they are both accurate? I've always used the gear/tire wizard but if these were messed up to start with assuming they will stay that way. I found a few olders excel files in the forums but links have since been broken. Thanks for the advice, i'll upload that new value and try it out!

Blake