D2801 TCC lock during upshift

[nevinsb]

I have a question about D2801.

The description says "Allow the TCC to lock during upshifts" but I am still a little confused.

If this is set to "No" does it unlock a torque converter during the shift, or does it just not allow it to go from unlocked to locked during a shift?

[Taz]

Hello nevinsb,

If D2801 is set to “No”, it may well mean either (or both) of the situations you described.

Sometimes the base OS parameters (OEM tables that EFILive doesn’t access) will override selections made (like selecting Lean Cruise enabled on non-Holden vehicles - without applying a *.cax file - the base OS overrides the selection, and there is no net change). This phenomenon also applies to TCC function, depending on vehicle platform and OS.

To confirm any / all of the above you will need to log the appropriate transmission parameters during operation - to see what your particular OS does (allows / doesn’t allow)

Is there a particular shift quality or function you had in mind for your vehicle ?

You’ve been doing this for awhile, so you probably already have transmission parameters that work for you.

There is a great transmission tuning tutorial by Joecar available as an additional resource. I also have a rudimentary set of transmission “if this, then that” parameters that I use - and don’t mind sharing to answer specific questions.

Regards,
Taz

[Taz]

As a side comment …

The OEM converter lock up disk (clutch) in the torque converter is definitely a “weak link” in any application making a decent amount of torque - as I’m sure is the case with your turbocharged engine.

Leaving the torque converter unlocked during upshifts also helps to absorb some of the “shock” associated with the shift - promoting longevity in the other driveline components.

There are torque converters in the aftermarket with Carbon Fibre and / or Kevlar clutch disks that are much more durable - and may lend themselves to locked upshifts.

Regards,
Taz

[nevinsb]

I put a 3000 RPM vigilante converter in mine, and after I did, my truck seemed to be hanging during a shift, and it would over-rev and I was having a real hard time trying to isolate it.

As much as I would love to log every single PID, I'm in Korea without my truck, so I'm taking some time to fix a few things in the tuning. I probably wouldn't have noticed this PID if it wasn't off in the 2003 tune and on in the 2002.

[Taz]

Given that you’re overseas … logging transmission PIDs will be hard to do !!

The following is just from my personal experience, others may have different experiences to share …

With a turbocharger you should be making a significantly more torque than stock, and the increased torque will probably begin at a much lower RPM level than a normally aspirated engine with the same gross output.

The 4L60E transmission valvebody and related components are slightly different in a 4.3 L V6 application compared to a V8 application.

The following chart is for 1999 models … but your 2003 will be similar, if not the same.

*** could not get the chart to copy ***

Max line pressure for V6 trans is 192 PSI, for V8 its 223 PSI


At the same PCS value (amps) the transmission line pressure is quite different between V6 and V8 applications. Also, a “loose” converter will make the shifts “feel” a little softer than with a tight converter.

My approach would be to maximize transmission pressure - and holding force on the 2nd – 4th band. I prefer to use a TranGo HD2 kit for the 4L60E – but there are several other good quality options. I find I get the shift feel I like by using a “Corvette” 2nd gear servo, and a billet or “super hold” type 4th gear servo. For the boost valve – 0.500 is the minimum diameter I use.

You get the trend - get the “hard parts” in the trans to bring up the mechanical pressure and band holding force ….

Follow this up by “tuning”.

Base Pressure:
· increase tables D0701 (Base Pressure 1>2 shift), D0702 (Base Pressure 2>3 shift), D0703 (Base Pressure 3>4 shift)

When increasing the Shift Pressure tables the graph of the values should increase from 0 PSI at the left side (low torque), to around 96 PSI at the right side (high torque). The slope of this line is generally “straight curve” from the lower left (0 PSI) to the upper right (96 PSI). I your case you could bring in more pressure earlier - to match the torque curve.

Shift Time:
· reduce tables D1108 (Desired 1>2 Shift Times), D1109 (Desired 2>3 Shift Times), D1110 (Desired 3>4 Shift Times) to around 0.2 seconds
· with a loose converter 0 seconds may be an option to firm up the shift feel

Torque Reduction:
· reduce tables D0801 (Torque Reduction 1>2 Shift), D0802 (Torque Reduction 2>3 Shift), D0803 (Torque Reduction 3>4 Shift)
· continue reducing table values (in conjunction with shift times) until you arrive at the shift quality you want
· the more Torque Reduction is reduced – the greater the stress on the drive train - may lead to component failure
· decreasing Torque Reduction to 0% - shifts will be very harsh

Hopefully this gives something to work with overseas …… and hopefully your 4L60E will hold up under the stress !!

Regards,
Taz

[nevinsb]

I already know i won't hold up to the new torque since the sun shell explodes without the turbo.

Thanks for the advice, I definitely got some new ideas to play with.

[InTruckDesign]

I would just like to say that Taz's quick little tutorial is spot on. I have the 4L60e in my tahoe with all associated "hard" parts plus a full performance/tow rebuild and my shift pressures are basically stock and I have been playing with shift times and torque reduction for a couple months now. I have found that the 1>2 upshift is the one to focus on, my 2>3, 3>4 have shift times at 0 and torque reduction at 0. My current 1>2 is set in a bell curve from .15 up to .25 and back down to 2.0 with torque reduction slowly added in to a max of 10%, as of now my shifts are very quick and firm, nowhere near harsh. Oh and I have a 2600-2800 converter.

[ScarabEpic22]

Id agree with Taz too, I cant speak too much for V8 applications but it is good to know the V8 4L60Es are slightly beefed over the V6 (and I assume I6) 4L60Es. For a V/I6 you are fine with a .470 boost valve and a Vette 1-2 servo, billet OD servo is even better. I have tuned a bunch of I6s and just the Vette servo makes a HUGE difference in shift quality (much better) but a boost valve makes them shift really positively. But not neck snapping, unless I really ramp the pressure up. Heck on my 02 TrailBlazer I6 with a Vette servo and boost valve I have to run LESS than stock line pressures on the 1-2 shift otherwise its brutal. With 0 TM and 0 shift times, held up to about 50k without a glitch.

[InTruckDesign]

As of now I am running less than stock line pressure on the 1>2 shift, finally getting closer to being happy with the trans. tuning.

[joecar]

I would just like to say that Taz's quick little tutorial is spot on. I have the 4L60e in my tahoe with all associated "hard" parts plus a full performance/tow rebuild and my shift pressures are basically stock and I have been playing with shift times and torque reduction for a couple months now. I have found that the 1>2 upshift is the one to focus on, my 2>3, 3>4 have shift times at 0 and torque reduction at 0. My current 1>2 is set in a bell curve from .15 up to .25 and back down to 2.0 with torque reduction slowly added in to a max of 10%, as of now my shifts are very quick and firm, nowhere near harsh. Oh and I have a 2600-2800 converter.Do you also have a shift kit (which one)...?

[InTruckDesign]

yes. I have the Transgo HD2.

I have been pondering the following...seeing how most of us know that adding torgue reduction helps soften the shift, does it also have any effect on the shift time and if so does anyone know what that would equate to. Basically for fine tuning shift feel/speed, so maybe add alittle torque reduction instead of upping the shift time by a small amount.

[joecar]

My understanding is that the PCM tries to meet the commanded shift time by the controlling the rate at which it ramps pressure to/from the commanded shift pressure, and that torque reduction is performed on top of that...

i.e. torque reduction does not appear to effect shift time from the logs I've seen [where the shift times were under 1 second].

[InTruckDesign]

Thanks joecar, that has been my understanding, just happen to notice that as I increase torque reduction the shift perceives to be slower. I am guessing what I feel is the motor just starting to laydown due to torque reduction on the anticipated shift. Hmmm...I am going to do some more logs, any special pid's I should look at other than the obvious ones?

[joecar]

There might be an EST_xxx_DMA pid also.

Maybe larger amounts of TR might just overwhelm the shift time.

I looked thru some of my old logs, and I see that my understanding is limited to shift times under 0.4 seconds on F-car and Y-car only. :doh2:

[slow67]

I do know that on F-cars, it pulls timing out ~.25 seconds before and after the shift, so the shift may be perceived to be slower.

[InTruckDesign]

slow67, thank you for that info. I will have to check my logs and see if the same is true with the truck/suv segments.

[slow67]

slow67, thank you for that info. I will have to check my logs and see if the same is true with the truck/suv segments.


It may not be exact, but thats the seat of the pants feel.