Sd Harsh Shift Troubles

[JoeR]

2007.5 Silverado, 5.3L

Sorry for what is probably a noob problem. I've done a bunch of searching, but the learning curve is pretty steep when you're first starting out.
This is my first tuning attempt. I bought my HP Tuner for an LS project I'm building, but then got involved in this truck yesterday.

Background: This truck was purchased at auction. It has been off the road since August. It's been to two dealerships and 2 independent repair shops. It goes into Reduced Power Mode whenever you drive it, but it sets no trouble codes, and never displays Reduced Power on the dash. The throttle just goes dead, with no other symptoms. In attempting to repair it, it has had 2 new PCMs, 2 new throttle bodies, 2 new gas pedals, 2 new Throttle Body Controllers, 1 new wiring harness and 3 new MAFs. (you should see the repair history on this truck!)
Nothing has changed the symptoms. I inherited it yesterday. I noticed that the problem goes away when you unplug the MAF. You can drive it anywhere, but the 1-2 shift is too harsh to drive it like that forever.

As a technician, I've seen that unplugging the MAF and putting a GM into SD Mode makes for high/hard shifts. It's quite normal and to be expected. I've also read here that the same thing happens when you change a vehicle to SD Mode with a tuner. If I apply both TCS patches the harsh shift goes away, but then Reduced Power Mode returns, so those patches aren't going to work for me.
Next I figured I would just slow down the 1-2 shift speed and reduce the 1-2 shift pressure. I've done this for all the shift tables I can find. It has absolutely no effect on the transmission. What am I missing?
I attached the tune. I've also recorded a road test with the harsh shift and attached it, if that helps.
Please take a look at the tune and tell me what I'm goofing up. Any help appreciated.
Joe

[J-CUE]

When this happens, do the doors lock then unlock at the same time the engine reduces power?
If so, it may be a wheel speed sensor that?s bad.

[DGS]

What tires are on it? Do they match front and rear. Built with P265/65R18.

[JoeR]

When this happens, do the doors lock then unlock at the same time the engine reduces power?
If so, it may be a wheel speed sensor that?s bad.

Interesting you say that. Previous shop thought it might be related to traction control and disabled the ABS without any change.
Thanks for the reply!
Joe

[JoeR]

What tires are on it? Do they match front and rear. Built with P265/65R18.

Truck is lifted 8 inches and has 37.5-22 tires on it. Way bigger than stock.

When I looked at my original post I see I really didn't have a clear question. I'd like to fix that!
What trans tables (or other tables) can I modify to soften the 1-2 shift while running in Speed Density Mode? Any adjustment I make doesn't seem to make any difference.


Thanks for the replies so far.

Joe

[DGS]

You might flash stock tune from repository and go from there. Found this one. You can compare them within the software. You only want to change one thing at a time. You want to see the result and not be clouded by too many changes at once. The tires could be an issue unless there is a calibration for that size (not likely). I run into vehicles at work that have wrong size tires and there is no cal to correct for speedo. It causes issues with ABS/Traction control/Shifting/Etc. I'd put stock set of wheels and tires on it and see where it's at in stock set up and see if you have issues. Then you can go from there. Actually I compared the trans areas and you made a lot of changes there. I'd put it back and go with the stock wheels/tires. If you work at a dealer you can borrow from a used vehicle or set of take offs from sales. That could rule out a lot if it has never been run with stock wheels/tires. P265/65R18.

[QTR FMS]

https://forum.hptuners.com/showthrea...-Speed-Density

not sure if it the same issue but check if you have any transmission code and disable it

[JoeR]

You might flash stock tune from repository and go from there. Found this one. You can compare them within the software. You only want to change one thing at a time. You want to see the result and not be clouded by too many changes at once. The tires could be an issue unless there is a calibration for that size (not likely). I run into vehicles at work that have wrong size tires and there is no cal to correct for speedo. It causes issues with ABS/Traction control/Shifting/Etc. I'd put stock set of wheels and tires on it and see where it's at in stock set up and see if you have issues. Then you can go from there. Actually I compared the trans areas and you made a lot of changes there. I'd put it back and go with the stock wheels/tires. If you work at a dealer you can borrow from a used vehicle or set of take offs from sales. That could rule out a lot if it has never been run with stock wheels/tires. P265/65R18.

'

The truck started with the latest cal available on GM's SI. You're right that I made a lot of changes, and none of them made the slightest difference in the 1-2 shift. When you're in SD mode, is there there a way for me to see what Trans Table the TCM is using? I'd like to be sure I'm modifying the correct one.
I'm not at a Dealer, so don't have other wheels to try, but interestingly the speedo is only off by a couple of MPH. I can't tell how they did it though. there's certainly no option for that size in the EBCM, and it does not appear they modified it with a tune.
I'm not a fan of lifted trucks, so I'd just as soon return it to stock and see what happens, but that's not what it's in for.
Has anyone else seen a truck go into Reduced Power Mode without any codes being set, or notification on the dash? This is a first for me.
Thanks again for the help.
Joe

[JoeR]

Thanks!, but no codes anywhere. Any chance you know how to tell what trans map the truck is using when it is in Speed Density Mode? Maybe if I can find the specific table I can make sure I am modifying it, and not molesting the other ones unnecessarily.

By the way, I dumped the original tune back in it last night and am starting over again.

Joe

[Philbar715]

Try playing around with these settings. If you set them all to disabled it should use the normal shift tables for shifting (under transmission diagnostics).

Also if you havent already, use the gear/tire wizard to correct for the larger sized tires.

Capture.PNG

[JoeR]

Thanks to everyone that contributed here. This truck is shifting normal with a Speed Density Tune.
Tune is attached.
Joe