4l60e shift issues after engine and converter swap

[400Horses]

I was suggested to move this post here.

Build: 99 Silverado 5.3,218/227 cam, ported heads, ported throttle body, LT's, 2000 stall, and Stage 1 Performabuilt Trans (installed when trans went out before
engine build).

Problem: Transmission shifts fine under light acceleration, but when rolling into the throttle or trying to accelerate hard it acts like its trying to flash stall between shifts. If I get up to cruising speed and roll into the throttle it downshifts correctly. Then pulls hard until it gets to the upshift again.

The trans shifted fine before I did the motor and converter. Can I make adjustments with HPT that will correct my issues. I'm still working on the motor tune and felt it easier to ask than to search the threads. Thank You for any help you can give.

I am having an issue getting a scan for VE adjustments but I can share the tuning I have done so far if it will help.

[400Horses]

ok. I have an update. The trans shifts fine at low rpm and shifts hard at hard acceleration its part throttle where it is still having the hesitation. attached is a 20 minute drive with LTFT an STFT scans along with my current tune.

[horsepowerguru427]

have you logged TCC lockup or TCC PWM to verify its a torque converter problem? you could lower the force motor current 5-10% to soften shifts. compared to my yukon thats a similar setup your line pressures are a little higher. or you could just use the scanner and unlock your TCC and see if it helps the situation any. My 2500 stall would lock and unlock at certain speeds and cause some problems til i got things where it liked it. increasing TCC PWM helped mine a lot also.

[TheMechanic]

Give this a try.
Trans>Torque Converter>Apply/Release>Speed>Release TPS.
Set all set them all at about 40% and re-drive. If that fixes it set this to a desired TPS that is you desire.
You know you have your full throttle shift speed at 5,200? Kinda low but it will keep a motor together I guess.

[400Horses]

The trans no longer has PWM. It is removed from Performabuilt. Thanks for the input though. I will make the changes that are available and give another update. Keeping the motor together is a top priority. Especially seeing that this truck is being driven by my 16 yrold as his first vehicle. There is a long story that also goes with the motor that is in it now.

[Alvin]

Heads up.. There is a issue keeping some 99-00 trucks locked up. From memory its a issue that can be resolved with a updated flash from GM.

If this is the issue I'm about the TCC will slip flair over and over again climbing a grade or passing without a downshift.. So moderate throttle locked up. Later OS's don't do it. I was able to get another one to stop doing this by reducing trans temps 205F to 165F.

[TheMechanic]

Heads up.. There is a issue keeping some 99-00 trucks locked up. From memory its a issue that can be resolved with a updated flash from GM.

If this is the issue I'm about the TCC will slip flair over and over again climbing a grade or passing without a downshift.. So moderate throttle locked up. Later OS's don't do it. I was able to get another one to stop doing this by reducing trans temps 205F to 165F.

Good call. There is two different updates and one is for growl. I think I remember that being TCC issue.
It has the other trans os in it for 1-2 shift harshness and not the growl concern. All other software is up to date

[400Horses]

Mechanic, I made the adjustments you listed and it didn't exactly fix the issue. The 1-2 shift shortened, 2-3 shift was soft, and like Alvin mentioned there was the slip flair on 3-4. I flashed the previous tune back in. The truck is still driveable, and shifts fine under light load. I'm trying to tune the motor and trans now at the same time so any tips I will continue to try. I will try the trans temp. The reason for the new converter was because the lockup clutch got cooked before the truck got parked. Everytime the cruise was engaged the lockup would slip, disengage, and kick a code spiking the line pressures. When did GM update the software? I had it reflashed in 2016. I appreciate your time. I will try anything to save the trans. The truck already got the motor for my tahoe. I'm not giving up my new transmission too.

[TheMechanic]

That's odd. The adjustment would only address TCC not shift timing, flare, or slips of any kind other than running the engine up to stall and with your 2,000 stall converter that is pretty tight. Not sure what direction to go at this point.

[Alvin]

I meant that the TCC will flair.. not the shifts. It's like there isn't enough pressure to hold them locked up at a cruise.

It feels a lot like the issue 8L and 10L's have trying the slip the TCC a certain amount going down the freeway.

[400Horses]

I work with a guy that use to be in the transmission business. He said that the TPS may need to be adjusted because it signals how much the line pressure needs to be. That being said I did a little work on the throttle body when I ported the heads. I didn't change the blade size just the area in front to smooth the transition up to the throttle blade to help the motor breathe a little better with the cam and head work. Do you think he could be on to something? I checked the fluid level and it is dead center of the crosshatch on the stick. I also haven't done any MAF tuning.

[400Horses]

I did a rewrite from a previous step in my tuning process that I had and it somehow has corrected the shifting issue. It still needs to have some adjustments, but I think it is good for now. The motor is my bigger concern. It just clicked past 500 miles and its time to do the first oil change. I compared my scan from today to another scan from the repository and noticed my TPS is reading 0.4% compared to 21.0%.

[TheMechanic]

I did a rewrite from a previous step in my tuning process that I had and it somehow has corrected the shifting issue. It still needs to have some adjustments, but I think it is good for now. The motor is my bigger concern. It just clicked past 500 miles and its time to do the first oil change. I compared my scan from today to another scan from the repository and noticed my TPS is reading 0.4% compared to 21.0%.

Post up the before and after rewrite so we can see what it is. Can never have to much info especially if it helps another person.

[400Horses]

The tune is the one that I have at the top from my first post. My scan that I did is attached, but I have bigger problems now. I got a call from my boys and they were driving to the gas station and tried to accelerate and it just reved in 3rd and the trans doesn't try to shift to 4th. I limped it home on backroads, but I'm not sure where to start. I still have 1-2 and Reverse. When it acts like it shifts to 3rd I cant feel the shift and it doesn't try to pull. its like the trans is in neutral. I had to slow down and let the truck downshift back to 1st before I could give it throttle.

[TheMechanic]

Hate to say this and hope I am wrong but "4L60e".

[400Horses]

That’s what I always hear. Problem for me is funding since I’m not only tuning this new motor but I’m also putting a new motor and trans in my 03 Tahoe. I would like to do an 80 swap but not sure I can swing it yet.