I noticed my truck seemed to rpm surge some at low speeds (40 mph) in OD w/ TCC locked. Last night I locked a bunch of data to support my claim. Starting at 40 mph, up to 55 mph, the slips speed og the TCC varies upto 200 rpm. (What I originally noticed by my tach needle) After 55, it locks up solid and varies by 2-3 rpm. It always happens around 55 mph, does it under, but not over. All along, the TCC is locked by LS1 Edit standards. What I noticed after looking at the data, is TCCDC (TCC Duty cycle %) changes. It's stable around 75%, no slip speed, as soon as I slow below 55 mph, the TCC DC drops to about half (35%) and the slips speed starts to ocsilate. Is this normal? Anything in LS1 Edit that needs adjustment?

2003 Silverado SS AWD
4L65E tranny w/ Yank TT3000 stall, and TCI shift kit.

TIA
I can send a copy of the EFI Live file if anyone is intrested.

 

Colonel, Kevin Winstead, Kevin Steele, anyone have a clue?

 

Hmmm...I don't know about that one. So if you're cruising below 55 MPH at a steady speed, the converter isn't fully locked despite the programming saying that it should be? But above 55, it is? I've never monitored TCCDC before so I don't know what it should be saying normally.

 

Exactly. It causes the RPM to vary about 200 rpm as the TCC slips. As soon as the TCCDC stikes 75%, ocsillations go away, when it drops to 35%, they start back up. So I'm trying to find out more about this parameter. I happened across TCCDC when I was logging all tranny data available w/ EFI Live, looking to log data to support my claim. When I started analyzing, I noticed that TCCDC seemed to trigger the effects. Hence, what is TCCDC?

I got some answers to what TCCDC is on EFI Live's forum, but still don't now how or what really controls it.

"The DC of TCC apply is controlled by the PCM to smooth the apply and release of the TCC. Under actual driving conditions, the PCM will vary the TCC PWM DC on apply/release to ramp up/down the apply pressure to control the TCC "feel"; it may also vary the TCC PWM DC at lower speeds (possibly depending on load) and this is what appears to be happening in your case; the displayed TCC DC is what the PCM is commanding the TCC PWM solenoid to do; under driving conditions the PCM will sometimes (I said "sometimes", but not always) command the TCC DC to be above 75% (at 75% the TCC is pretty much locked under light to medium load); the PCM has a ramp-up profile to apply the TCC in a controlled (no surging) manner; same with ramp-down; in 3rd and 4th gears under cruising load the TCC DC will generally be at around (or so) 75%, and will vary down from there as the load is changed (increased or decreased); a sudden load increase will cause a full release until the the engine "catches" up (allowing the TC to multiply torque as needed); a less sudden load increase will cause the PCM to reduce the TCC DC (i.e. a partial release) to some extent allowing some slippage preventing the engine from overworking (bogging down), but too much slippage will wear out the TCC lining!"

 

Have you made any transmission tuning changes already, and are you getting any transmission codes?

 

As I noticed before, the RPM moved around 40mph in 4th gear w/ TCC locked. I went out on the highway, started at 40 mph, and slowly sped up using the cruise control untill the TCC slip speed was 0. I noticed this happened around 55 mph. I then spent some more time speeding up and slowing down, centering around 55 mph. I could make it oscillate under 55, and quit ocsillating over 55 mph at will. The spikes in TP in the .efi data is from speeding up and slowing down 1 mph by use of the cruise control. The TCC 4th gear lock up at 25% TP is set to 44mph, thus meaning the TCC should be locked, but this does relate to our prior conversation on how the TCC PWM DC works. I have gotten a shift selenoid error twice in 2500 miles after the install. I doesn't allow the tranny to shift into first, but once cleared, work fine again. I noticed others get this same error after shift kits too.

The main question is, is it normal? Did the stall TC just make it more noticable? Did the TCI shift kit change something here? This is were I seem to be stuck. Any help at all is appreciated.


EFI Live v6 log file of the ocsillating TCC slip.
http://home.mchsi.com/~mallett396/trannyfix.efi

EFI Live v6 log file of a quick blast after I logged the ocsillating data.
http://home.mchsi.com/~mallett396/trannyWOTafterFix.efi

A quick Excel picture of TCCDC vs. TCC Slip.

 

This all seems very like the problems I had with the TCC
slipping after my TCI Streetfighter install w/ B&M fluid.
The TCC just wasn't holding against moderate throttle.
It's better now that I've gone back to Dexron but every
once in a while it still slips before unlocking. I think it
is something like, the PCM has an "idea" of how much
TCC pressure is needed to hold against a set amount of
output torque, but this is based on the stock clutch
material & fluid (plus some margin I reckon). But an
aftermarket converter might have a clutch material that
has lower friction and needs more pressure (PWM duty)
than the PCM "thinks". Dunno if it has any ability to
"learn" about slip & PWM but I'd sure like to get mine
changed to run a little more pressure.

Do you find any Edit tabs for something like TCC PWM
duty vs load? What if any TCC params do you have
available?

I'd like to know this, 'cuz I'd have to ask the Predator
folks to touch up mine the same way in a custom tune.

 

I do have Mobile 1 Syn Fluid in the tranny after the install, I did forget about that. The only tables is LS1 Edit that I have are TCC lock-up TPS vs gear. This tables tells the tranny at what speeds to lock the TCC based on TPS input. Like I said before, this value is set to 44mph at 25% TPS. So, it's TCC is locked at above this level, or al least until for TPS is given to un-lock it. I see that Superior transmissions has a PWM elimination kit, but I want that to be a last resort.

Again, anyone with ideas?

 

"I do have Mobile 1 Syn Fluid in the tranny after the install"

I noticed in another thread that FLP said not to use synthetic in their Level 5 tranny, which includes 4L65 parts. You might try a flush and regular fluid unless your builder told you to use the Mobil 1 as part of the warranty

 

Hey Mallett- I am fighting the EXACT problem with my truck. Don't bother with the Superior PWM kit-I put that in along with a new internal harness/TCC solenoid a few weeks ago to no avail. I have a Midwest 3000 converter that supposedly has the carbon clutches necessary for PWM systems. I have adjusted the TCC settings in edit and that didn't help either, It is VERY annoying when you are just trying to cruise through town and I know it has to be hard on it. As a side note I don't remember it having this problem when I first built the trans and put in the conv. (about 10,xxxmi ago) I have just about decided it is a converter problem. I guess I should call Midwest and see if they can help. I use regular Dexron and add a bottle of Lube Guard. I hope someone can figure this out-it is driving me nuts!!