tcc lockup and unlock during normal driving

[4.8t]

i've search and now my eyes hurt lol. at about 40mph light driving my tcc locks up. it does make a grrrrrrrrrr noise but just figured it was the torque converter. anyway when i'm in traffic and i'm cruise right at the 40 mark and i'm behind a car and i have to let out of the peddle for a minute and then get back in it, it unlocks and locks and unlock and locks and it kinda drives me up the wall. is it suppose to unlock when you release the throttle? i'm guessing so from what i have found just want to make sure its not gonna screw anything up.

now about the grrrrrrrrrr. its just a rattlely grindy but not really grindy noise its hard to explain. is this normal with a yank or are they normally really quiet or what?

[jimmyblue]

Raise your minimum TCC PWM duty cycle to 98% and
see if this goes away. Allowing a small converter to be
fed half-assed pressure will let it slip / chatter too much.

Hard lock/unlock is more likely misfires (probably false,
but still) and you will need to raise the misfire threshold
values until it settles down (or jump straight to the
punch line and kill 'em all, but shaving on it is better
philosophically).

Be sure to leave enough "deadband" between lock and
unlock MPH, to accommodate a little pedal / throttle
flutter. On drive-by-wire setups the throttle can move
around on its own, right? For shifts I like to have 2MPH
in 2nd, 3MPH in 3rd and 4MPH in 4th; keep a 5MPH gap
or so, in the TCC table lines.

[4.8t]

it holds fine just when you let off the gas it unlocks and when you roll back into it it locks back up is this normal? and its not a small converter by any means. it same size as stock. and when i did my shift kit it came with a piece that said it will be able to lock up any after market high stall torque converter. i'll ask yank about the noise again. oh and i guess its more of a buzz than anything.

[98A4LS1]

Increasing the misfire threshold values helped in my case. Changing to a 98% minimum TCC duty cycle did not work in my '98 with no other changes to the tune. Not sure if its a 1998 thing or not but the trans did not like it. Stock minimum TCC duty cycle settings in a 1998 Z28 are 10 across the board.

[4.8t]

yeah i don't think that this is my problem. the noise i hear i think is a low speed high load vibe from the drive train. i listened to it again today and in my extcab truck i hear the noise more in the back seat than anywhere.

[dlclarkiiRegal]

I have the same grrrrrrr sound with my 3750 stall, I'm searching right now to see if I can fix it with the new TCC duty cycle feature in the new v.12.

[LittleSlow1]

I have the same noise too, its the torque converter. mine is bran new has less than 500 miles on it now.

[4.8t]

i think mine is more in the drivetrain than the tc. still does it. it real loud when towing.

[02sierraz71_5.3]

I have the same problem with mine locking/unlocking at 40mph Ive even tried extending shifts to get around it. Im gonna try disabling the misfire completely Ive already tweaked those tables for the cam but who knows.
It takes very little tps change at speeds near shift points for the damn tcc to unlock also its very annoying.
Whenever I command the tcc lockup clutch it locks and holds at 40mph no problem, even if I let my foot off the throttle?

[LittleSlow1]

I set up my TCC to engage at 43 mph and disengage at 38 mph. It seems to be a little nicer to it at slow speeds.

[02sierraz71_5.3]

It takes very little tps change at speeds near shift points for the damn tcc to unlock also its very annoying.
Whenever I command the tcc lockup clutch it locks and holds at 40mph no problem, even if I let my foot off the throttle?

I maxed the misfire tables and it helped with this some

[MNR-0]

That grinding noise is th econverter clutch slipping. Its locking up too early and/or has too little apply pressure. I woudl suggest raising the LU points by 5mph and see what happens at the TPS position.

[1badc10]

That grinding noise is th econverter clutch slipping. Its locking up too early and/or has too little apply pressure. I woudl suggest raising the LU points by 5mph and see what happens at the TPS position.

That sounds like my issue. TCC doesn't apply at all w/o using the VCM Controls. Most times, that doesn't work. Vibration is evident @ 90+ mph.

[MNR-0]

Yanks usually have decent LU clutches. If you are getting slip at 90+mph you must be at WOT? Without supporting tranny mods, even Yanks will struggle to fully engage at WOT. I dont lock mine up at all at any WOT.

As Jimmy said, increase your PWM apply to 100 and offset to 98. Other than that, all you can do is raise the LU points. If it still grinds, check your tranny fluid or add some viscosity modifier. If that fails, I would lean to the converter LU plate being glazed or too far gone to be of use. In that case, send it back for a new clutch.

[S2H]

also if you are having locklup troubles you can log TCC stuff ans you will see unlocked/Locked..or -3- which is misfire related...
you can then as a test go to yoru engine diagnostics tab and hit the misfire tables..take them all to the highest value possible and retry your lockup again...
if it still wont lock then the thing either cant get enough line pressure in ther to hold or the LU clutch is toast...
you can always comand a lower force motor current in the VCM controls for a short term test...(lower voltage is more pressure)
if the combination of those two doesnt help..then you know your LU clutch is hosed