How to soften part throttle shifts: time or pressure?

[Supercharged111]

My fresh 80E swap is hitting too hard at part throttle, about as hard as WOT. I wonder if I'm to blame here. It has a Superior shift kit with everything set to "towing" as that's the truck's reason for existence. Well, that and to authorize me to be a man card holder. Part throttle shifts are much harsher than they need to be and I'm wondering how I can alter this? I didn't zero out the shift times this time, I set them to .2 across the board. I'm wondering if I should increase that to .4 in the low torque regions? What should datalog? Torque vs. TPS, but showing what? Time or pressure? I like the WOT shifts, kind of slingshots you when it hits.

[EagleMark]

With a shift kit you should go back to all stock settings. Then see if you want to do anything. Shift kit is mechanical change, some times no need for tune change.

I've read some of those threads on tranny tuning I have linked in my thread and I have to disagree with changing Desired Shift times to 0.00 with a shift kit! Will be very harsh as the shift kit already made an adjustment there.

Here's my PID list from recommendations in writ ups. Not sure it is correct for 1998 PCM and 4l80E but will get you going.

[Supercharged111]

Hmm, that's an easy thing to do. I still have the tune Lextech gave me, I'll just put shift times back to stock and see what happens. I didn't monkey around with pressure, I'm deathly afraid of touching that. Now shift speeds on the other hand, ugh, that's based off of feel. I bet I have a half dozen flashes left on that until I'm happy!

[EagleMark]

Shift speeds I have played with a lot and can change how a vehicle drives and feels tremendously! Always do them with both Up-shift and Downshift tables, Downshift must always end up lower then up-shift.

Hot I usually leave alone.

Cruise tables are usually a little higher then Normal tables.

[Supercharged111]

Stock was retarded, they overlapped! Well TCC did, the truck didn't know what it wanted to do at first. I'm using that Excel spreadsheet from the stickies right now to build what I think is a better shift pattern to try tomorrow on the way to work.

[Supercharged111]

I noticed the hysterises (ii?) were larger when in cruise mode than in regular mode on my 4L60E, I kind of liked that because cruise is dumb and doesn't anticipate things.

[EagleMark]

Stock was retarded, they overlapped! Well TCC did, the truck didn't know what it wanted to do at first.
Of course stock is retarded! That's why we fix them... :anitoof:

I meant just the Desired Shift times because of the shift kit, not the whole thing...

I didn't see any overlap though in TCC? Oh well, you'll fix it.


I noticed the hysterises (ii?) were larger when in cruise mode than in regular mode on my 4L60E, I kind of liked that because cruise is dumb and doesn't anticipate things.I agree and set them up the same, give cruise a little more breath room before you end up with a full throttle down shift.

Problem with that on some PCMs I've noticed is the Cruise pattern is in effect with switch on, even if cruise is not engaged.

Comparing trans settings I've noticed the same Normal and Cruise is usually in HD tow option rigs? Higher gears maybe make is easier? Some of the best all over stock trans settings are from the HD trucks. Worst are LD trucks or non performance cars..., they are more like cars one big SLLLUUUSSSHHH... want to see a car totally change it's whole attitude? Do a trans tune on a 1994 to 1997 Buick RoadMaster with an LT1. Wow!

[joecar]

With shift kits, you would typically set the tune as follows:

- set shift times to zero (which typically lets shifts proceed as fast as the shift-kit-modified hydraulics allow); also try 0.3s and compare with zero.

- set shift pressures to stock.

- use shift torque reduction to soften/adjust the shift feel (do not reduce shift pressures, and do not lengthen shift times).


If you still have excessive shift feel (harsh jerk) then you need to take a closer look at the shift kit install, there may be options on line pressure (various springs) or accumulator pressure (various washers/springs).

[Supercharged111]

OK, shift times zeroed and TR returned to stock. I have a feeling I'll be adding TR in the lower torque regions, but how do I systematically determine that the truck shifted harshly at XX NM of torque and know to add TR at that value?

[Wheelz]

You can log torque output to know where it thinks it's at when it shifts

[IJ.]

You can log torque output to know where it thinks it's at when it shifts

Did it this way during the week, worked perfectly thanks for the heads up Wheelz :D

[Supercharged111]

I just logged engine torque and then put it on a guage on my dash display and stared at it while the truck shifted. I made it a lot better than before, but what type of map should I build to do this a bit more scientifically? Are you guys pulling much more than stock? I just want to know when I've gone off the deep end.

[EagleMark]

Seriously, with a shift kit and leaving settings to stock! You should not have any harsh shift issues to deal with.

Now your back to stock TM and removed all shift times and having issues with harsh shift... so your going to take out TM???

I just want to know when I've gone off the deep end.I think we are there! :music_whistling_1:

I was looking to make a Map for GM.TRQENG but it's only one row, no axis so I did not figure it out earlier today...

[Supercharged111]

I'm kind of torn because my intent with the shift kit was to quicken up the shifts to prevent wear when dragging a trailer, not bang bang through the gears on my way to work and back. I can say that adding (not taking away as I'd done previously, I now have more TR than stock in the low torque regions) TR made a very noticeable difference. I believe that putting shift times back to stock would result in lowering line pressures. Now I'm left with the job of being an engineer and deciding which is the smartest way to reel this thing back in, because lowering line pressures seems like undoing the shift kit. We know stock works, but stock sucks, I'd just hate to deviate in a way that'd shorten the life of the trans.

[EagleMark]

The shift kit changes pressures for the better. It can't change time as that is up to PCM...

What is it like with stock TM and stock shift times? This is what the kit is designed for! No tuning necessary...

[Supercharged111]

I have yet to try stock shift times and I've got a few barley pops in me so that'll have to wait for tomorrow. I never drove it with stock shift times, that was the first thing I changed before ever firing the truck. HD2 users complained of shift kits "undoing" themselves, that's why people recommend zeroing the shift times with a kit. For as little as I did, this kit sure has balls though.

[EagleMark]

The Adaptive learn is going to be next topic in my trans thread.

D1107 I believe is the cause of Adaptive Shift learn taking out what shift kit put in.


Determine the limits to which the transmission adapt values can modify the high line pressures.
This applies to all transmission shift patterns (1-2, 2-3 and 3-4).

Or maybe it's taking away in D1101, D1102 and D1103 ?

So instead of going to 0.000 on shift times maybe 0.1000, until we can figure out how to limit Adaptive Learn from taking away what shift kit adds?

[Supercharged111]

I set all mine to .2 initially and it was still good and rough. Again, the shift kit is money at WOT, but the shift intensity doesn't seem to linearly decrease with load.

[Wheelz]

On the LS1B, EFI live says to set shift time to 0.0 to disable adaptive learning (the descriptive text for each shift table). This would allow the pressure table to solely control how quick the shift occurs, which is how I would dial it in, then maybe log shift times when your done and set the adaptive learn to match if you want to re-enable it.

If you don't disable adaptive learning, or figure out how to set your shift times to approx what they are actually at now, adaptive learning will most certainly make your truck shift like stock after several miles.

For torque management, I've had real good success so far building the table so no reduction occurs till (I picked) 200 ft lbs then reduction limits torque output to 200 ft lbs for all following increased torque values. I can post up my tune tomorrow if anyone wants to see it. Id kinda like to compare it to some other people's tunes.

[hog]

There are many a tuner that zeo out shift times when shift kits are installed, simply to disable adaptive shifting strategies.

Torque Management is much more noticeable at part throttle in the GMT400 trucks, than at WOT. Not sure if much is taken away at WOT. Part throttle shifts with stock TM levels make it feel like teh truck is "stopping" during the shift. On wet roads no TM will cause wheel slippage during a 1-2 upshift, with stoock TM levels, its tough to get part throttle wheel slippage in the rain. I, welll versed in such manouevers.

peace'
Hog

[Supercharged111]

That's pretty cool, limiting the torque at 200 ft/lb. I was logging in NM yesterday and it was a bit crashy at times around 120NM and 200NM depending on the gear. I'm going to view in ft/lb to see where my charts are truly at.

A little OT, but I've lost a TON of advance, I was getting 24* tapering to 19* WOT when it's commanding 33. It's across the board and I logged zero knock. This probably explains the pronounced gutlessness of the truck now, I thought it was all transmission but it appears that's not the case.

[Supercharged111]

According to my log I only generated a max of 145 ft/lb torque, don't know what to think of that. Perhaps this spark issue is causing some odd torque readings? I should also mention that I'm SD tuned.

15725

[EagleMark]

On the LS1B, EFI live says to set shift time to 0.0 to disable adaptive learning (the descriptive text for each shift table). This would allow the pressure table to solely control how quick the shift occurs, which is how I would dial it in, then maybe log shift times when your done and set the adaptive learn to match if you want to re-enable it.

If you don't disable adaptive learning, or figure out how to set your shift times to approx what they are actually at now, adaptive learning will most certainly make your truck shift like stock after several miles.

For torque management, I've had real good success so far building the table so no reduction occurs till (I picked) 200 ft lbs then reduction limits torque output to 200 ft lbs for all following increased torque values. I can post up my tune tomorrow if anyone wants to see it. Id kinda like to compare it to some other people's tunes.That explains a lot!

But if Adaptive learn is already done? Is it stored for next time? Can it be cleared?

I'm going to play with this a little today and log some PIDS like Adaptive shift Cell Number GM.ADPTCELL but I'm not sure where to find what/where cells do? Then Adapt Shift Modifier it 's units are CORR so may tell more. GM.ADAPTSHIFT

Still seems D1107 I believe is the cause of Adaptive Shift learn taking out what shift kit put in.


Determine the limits to which the transmission adapt values can modify the high line pressures.
This applies to all transmission shift patterns (1-2, 2-3 and 3-4).

Or maybe it's taking away in D1101, D1102 and D1103 ?

But first have to understand how this is all applied in code, where it starts, what it's looking for and how it makes the adjustments so it can work without going to far?

[Wheelz]

What appears to be happening on my truck is every time I flash it it loses what the adaptive learn values were. So it takes a week or so of driving to get back to where it was because I don't have my pressure tables close enough.

And also, I'm thinking about linearly rolling the torque up from 200 to about 250 to help firm up the shifts at WOT. It feels like a very quick manual shift right now and my exhaust note goes quiet during the shift because of so much reduction. I have a bone stock 4l60 so I don't want to work it too hard though.

Ill get my tune posted up shortly

[joecar]

Also log GM.TFMPRS to see how the PCM is commanding torque signal pressure

(see how torque signal pressure affects line pressure in the 4L60E Reference Material thread).

[joecar]

What shift kit did you install...?

[Wheelz]

This is my most recent tune. I've been playing with when I want my TCC to lockup relative to the shift. This one just happened to be when I wanted to see how it drove if it was always locked in 2,3,4.

15726

[Supercharged111]

What shift kit did you install...?

Superior, it's a really simple kit.

[EagleMark]

Also log GM.TFMPRS to see how the PCM is commanding torque signal pressure

(see how torque signal pressure affects line pressure in the 4L60E Reference Material thread).Went through and read that but did not catch on to the purpose, so not quite sure how I can interput data from it to? Or exactly what GM.TFMPRS is? Obviouisly PRS is pressure, what is TFM?

Here's a screen shot of 100% 1>2 shift and the GM.TFMPRS si going up even before the shift, then spikes at shift, also spikes at 2>3 shift.

15727


Even in logs with just 25%TPS the GM.TFMPRS does spike although less before shifts.

[joecar]

TFM = Torque Force Motor = the old name for Pressure Control Solenoid

any changes you make in the pressure tables and the time tables will show up directly in this pid;

also, any changes you make to the VE and/or MAF tables will indirectly show up here also (if you underscale, causing the torque computation to be low, you will see TFMPRS show low psi).

[EagleMark]

Nice! :anitoof:

This would also explain why you advise to log TPS and or MAP! I can see the correlation now!

And the reason GM.TFMPRS raises during a shift?

[joecar]

...

And the reason GM.TFMPRS raises during a shift?While holding a gear, a clutch or band does not require much pressure to hold;

but, during a shift, [at least] two things must happen:
- the releasing component ramps down (i.e. goes from locked to freewheeling),
- the applying component ramps up (i.e. goes from freewheeling to locked);

the applying component, prior to this shift, may be stationary, spinning slowly, spinning in reverse, or spinning forward at speed... and must now come up to rotating speed or to become stationary (i.e. must undergo a large transition)... a pressure spike is required to achieve this in the most timely manner (see shift time tables).


There are two concepts:
- base pressure (determined by engine load/torque/rpm),
- transition pressure (determined by physical shift requirements).

[Supercharged111]

Wow, I ignored this for 2 weeks. I needed to pull my car to the track, so last week I re-engaged the tune. I had lockups cross modulated with shifts, that's where the harsh part throttle shifts were coming from. Now it shifts normal at part throttle and only makes your eyes go funny at WOT. Speedo was off, I don't know how it wasn't the first time I checked it. Weird. 2nd is locking with moderate to full throttle somewhere around 3000 RPM which gives a retarded 2-3 no matter what the throttle position. Who the hell at GM thought that was a good idea?! Here's my latest and least bad tune.

15852

[Supercharged111]

also, any changes you make to the VE and/or MAF tables will indirectly show up here also (if you underscale, causing the torque computation to be low, you will see TFMPRS show low psi).

So is this the reason the 4L60E got rough once I tuned my VE map? Shifting from park to drive it was very noticeable, I always felt it was excessive, but my truck would run stoich without O2 intervention so. . .

[Supercharged111]

I finally found the problem with the harsh shifts. They were still overly harsh even after I made them less bad. I'd been running SD on the black box and apparently that's not without its consequences. I was talking to a professional tuner who mentioned that there are some 2D MAF based tables for altitude correction, apparently the same can be said for the shifts. After plugging the MAF back in I can't even feel the shifts! They're still really quick though, so now to un-neuter the transmission tune from last year when I was trying to cover up the real problem.