2012 Sierra 5.3 Slow 3-4 shift!

[00HardtopSS]

Help a new guy out!

I have a 2012 sierra 5.3, 6 spd auto - new to tuning.

Make a long story short, the lack of throttle response from the vehicle off the lot got me wanting to make some changes. It drove like a turd at part throttle.

I started doing a lot of reading on the forum, I found a tune that sounded like what I was looking for and did some borrowing off of that (in fear that I'd ruin something if I just went at it totally on my own) and have been using that as a base.

Overall, the truck drives so much better. However the problem I'm having is that the 3-4 shift at mid-throttle is awful. It is real slow. Can some knowledgeable people take a look at the log/tune and offer some thoughts?

I know the log is kind of long: the 3-4 shifts can be found at
3:56
4:47
6:05

I don't currently have a wideband hooked up, I hope to get that done in the next few weeks.

[gofish7]

On the top of the shift pressure page, the value of 109 needs to up increased to 175 and that will command more pressure to all the cells you are requesting to have 150+ psi. So, start with that and report back. but your shift adder page looks fine but you might have to do some tweaking in the final shifts or initial sections.

[00HardtopSS]

Good call fish, that did help.

However that 3-4 shift is still "slower" than the rest? When I say slower I don't necessarily mean the changing of years is slow. But what I mean is there is a long lag in the power.

It's like it engages quickly enough, however the truck doesn't resume acceleration for a few seconds from the start of the shift. You can see this in the log I posted, as it appears timing is pulled for a duration of about twice as long as it is on all other shifts throughout the log. Must be a torque management issue?

I'll try to get another log posted tomorrow with the higher max pressure value.

[gofish7]

It could be TM but it's most likely not re-engaging the clutches to finish the shift. If you haven't touched TM, do that first and then report back. If you have, then you need to touch up the final shift and the initial shift just a hair to get what you want.

[c.u]

One thing i would change. The down shift are set higher then the up shifts.

[00HardtopSS]

cu - Wait, it's not supposed to be that way? Ok, now that's fixed lets move on to the next thing.

Fish - The shift torque factor on the 3-4 shift is set to .5000
To see if what you are saying is true - that the re-engage is slow, couldn't I include shift times PID in my scan to verify? I'm not familiar with the tables you mentioned so I don't feel comfortable going in there to modify. I'll have to look into that more.

Thanks for the help and in the mean time - I'm open to any other critiques or suggestions.

[gofish7]

When I say touch up, I mean decrease them to have the desired upshift completion. Your adder is good...now its time to decrease the final shift which will decrease the shift time needed to finish the shift. Word of warning...start in 10% increments (.9)until you get close then go in 2% or (.98). I would start in the lower tables like 1-5 as these are part throttle and WOT usually doesn't have this flare problem.

Enjoy and check back.

[gofish7]

cu - Wait, it's not supposed to be that way? Ok, now that's fixed lets move on to the next thing.

This doesn't matter as rpm has to be met as well before it will upshift at WOT.

[00HardtopSS]

Ok, thanks fish. I'll look into that and get back. I haven't been motivated to do it and drive and get logs mainly because it's been about 4 degrees and the snow has been falling for days.

I'll report back.

[00HardtopSS]

Hey Fish - Came back around to taking another look at this. Not sure if I'm understanding your previous posts correctly..

You're suggesting I decrease the values in columns 1-5? So when I decrease them by 10%, they will be lower than the 6-9 columns

Thanks

[gofish7]

Yeah, you can start with that or you can take the whole table and reduce it by .8 and that will tell you if you are on the right path. Could also need more offset, etc preset volumes but....start with teh final shift as it doesn't look like it is finishing the shift fast enough for your liking.

[00HardtopSS]

Fish, I ended up reducing all columns by 10%. It does seem better.. Most of the time.

I only did this in the "shift final - normal" table, and not the special table.

It seems like under real light throttle it can still be long. So my question is this - how do I know which cells I should further reduce it? Anything short of trial and error? (I know that its the lower numbered cells, but what im asking is there a way to know specifically what cell needs adjusting?) Also, what would the symptom be if I went too short?

[00HardtopSS]

Here's an updated log file.

Yesterday, I loaded the file yesterday with the reduced final shift on the 3-4. Today when I was driving home from work, (as previously stated) the 3-4 felt better at times, but I felt like the 4-5 was long now too.

So I did the same with the 4-5 final shift table (reduced by 10%). Attached is the log I took after.

The 3-4 shifts and the 4-5 shifts are long (0.7 secs) of timing pulled after the shift.. As you can see from back in my original log, the 4-5 shifts there were not a problem then. And I don't think anything in my cal changed since then that would make them longer??

Thoughts? This is kind of worrisome to me

[gofish7]

Post your new tune....also, PM me your email address and I'll see if I can't help you out a bit more.

[00HardtopSS]

Thanks Fish - appreciate the mentoring