rgvsierra

iTrader: (7)

what causes the tc to clatter when locking up, i just got a PI installed about 2 or so months ago, and right now with low speed and very little throttle i get clatter, if i give it gas to lockup a litter higher it wont do it. just makes a funny whirling noise though..

will putting a shiftkit help this go away, how about the pwm, should i try and work on that, or is it to late and the tcc is ruined?

onyx_rock

iTrader: (8)

Quite a few people have this as I do and have researched it a little. Fuddle claims it to be PWM as you stated. He sent me a supposed hardware fix that did not correct it and I had it tuned and upped the line pressure and that didnt really correct it either. Jimmyblue claims to correct it with tuning and has quite a few posts about it. I am not sure if it is a problem though or not. I have a guage and my tranny never runs hotter than 180. Usually aroud 165 is normal. I have just dealt with it for now,

Sport Side

iTrader: (6)

Where can I find some of these posts by Jimmy, on how to fix this problem?

jimmyblue

iTrader: (11)

Think of it like wheel hop; you don't have enough down
force on the rubber to keep it from skipping off the
pavement.

PWM on the TCC apply softens up the clutch pressure so
it can chatter. Just like different tires have different "hop
characteristics" (some smear, some stick & jump), the
different clutch materials out there have different slip
characters. The ones you'd pick for dragstrip, WOT-lock
abuse are tough and "grabby" while the ones that GM likes
for your Aunt Sally's V6, are picked to slide smoothly.
Though even these, using the wrong ATF can make groan
and chatter (read the bottle, "newest anti-chatter specs,
blah blah blah). Some clutch systems hate the friction
modifiers in Type F and will squeal big time, even though
old TH350 organic tranny clutches used to like it for more
grab.

You can make the PWM always 99%, min and max, and
get all of the modulated line put to the TCC. Which is
better, but 100% of not-enough, may still be not enough.
GM didn't want to push line pressure up off the floor at
cruise. But 7% of not-enough, sucks worse.

PWM doesn't make the noise, it just gives the clutch a
light enough pressure to let it bounce/chatter/squeal.
Just like fingernails on the chalkboard need the right,
light pressure or you won't hear anything.

DanZ28

iTrader: (5)

I remember this issue several years ago. I had the same thing with my Yank 3500 TC and it was the lockup clutch slipping and adventually it glazed and continued to get worse. There was alot of speculation about certain mods causing the issue, one was ported MAF ends. I just switched it to another TC from Yank (PY3400E) and never had the problem again. Of course they updgraded their clutch material and started using bigger clutches. I think messing with the PCM is just a bandaid. Also, Yank had some sort of additive that you could pour in the tranny and that fixed the chatter for alot of people. my .02

Dan

Sport Side

iTrader: (6)

It seems that the later you lock the converter up, relative to MPH, the less chance of a clatter or vibration, you'll hear/feel...

I seem to get both with anything below locking it up at 50 MPH. I set the min max to 99 by the way.

Can I do anything? I'd like to lock up the converter much sooner.

jimmyblue

iTrader: (11)

You can raise the low-load line pressure by reducing the
force motor current in the left-hand (low line%) columns.
But this may or may not be in the interests of long term
reliability (if you can say that, and "4L60E" in the same
sentence without laughing).

Sport Side

iTrader: (6)

I'm using a vacuum modulated transmission.

BlackHawk T/A

iTrader: (3)

A revised TCC valve will eliminate PWM mechanically and permanently.

RevGTO

iTrader: (12)

As in Transgo shift kit.

jimmyblue

iTrader: (11)

Maybe you want less "modulation" at high vacuum then;
is there any adjustability there? Vacuum modulators
only reduce line pressure (same as force motor, just
more simply). It might want a smaller bleed-off orifice
or a higher rate spring dealie or whatever (depending
on whether you want to change the floor, which is
what I think you want, or the wall).

FLT

iTrader: (1)

A shift kiit will more than likely fix your lockup chatter. The problem is probably the tcc regulator valve in the valve body. A shift kit with an updated seperator plate might just cure your problem. Good luck, Vince.

rgvsierra

iTrader: (7)

just wanted to post this for anyone else searching for this problem,
but you were right on,
i put in a newly built tranny with lots of parts the local buildier recommended , transgo being one of them and now my lockup clatter is completely gone.
hope no damage was done that might have shorted the converters life

PonchoFan

Lockup chatter is not good. It can lead to the clutch material shredding and destroying the trans.
Yank had so much trouble with kevlar clutch chatter in the ST3500 series that they quit making them. They upgraded to carbon to cure the probllem. I had one that ran great for 2k and started chattering bigtime. Lube Gard friction modifier helped somewhat but never cured it.