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...

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