Need help diagnosing TCC shudder

[Dennis12345]

Hi Ya'll

First time poster been lurking for a while.

I've got an 04 trailblazer 4x4. I picked it up last year with a bad transmission and dropped a junkyard one it it.

Issue is I've got about 25k on the thing now and its starting to have a pretty significant shudder that seems to be torque convertor related, my observations so far are:

-Seems to be worst while under slight acceleration
-Stops if I lightly touch the brake(while keeping my foot on the gas)
-seems to happen most violently between 45-50mph
-seems to smooth out above 70mph
-happens on and off with out reason
-Doesn't happen under 35mph
-Currently has no transmission related codes(just an evaporator leak)

so from what I've seen this appears to be TCC related, now my question is it the torque convertor or is it something else? I read somewhere that a bad valve could cause similar issue, I just want to be confident before I take the time to pull the transmission again.


Thanks in advanced!
-Dennis

[bartonmd]

Standard 1999+ 4L60E issue. They pulse width modulate the TCC solenoid on these to keep 3-4% slip at all times, so the steel piston is always moving back and forth in the aluminum bore in the valve body. The piston wears out the bore in the valve body, where it always goes back and forth, but not at the higher % PWM end of the bore. So, it slips too much, then the TCM tells it to apply harder, then it gets to a non-worn part of the bore and locks up too hard, then it backs it off and it slips too much, and back and forth. There's no hysteresis programmed into it, so it just keeps doing it.

There are 2 fixes. If you've got HPTuners or something like that, just make the minimum pulse width 90% (I pre-preemptively did this on my TB, and picked up like 1mpg from it). Otherwise, you get the kit that fixes that problem, which is a non-PWM TCC regulator valve and a reamer to clean up and enlarge the regulator valve bore in the valve body.
http://www.sonnax.com/parts/2458-tcc-re ... -valve-kit

Mike

[Jrgunn5150]

Yep, I fixed mine with the Sonnax Sure Cure kit.

[bartonmd]

Nice... So, he signs up and asks a question, comes back later that day and likely sees the answer. No "thanks" or anything, and hasn't been back since. Awesome.

Mike

[Jrgunn5150]

As they fall into the 1500 dollar range, or the hand me down from mom and dad range, we'll probably see alot of it

[bartonmd]

Yep. I get a lot of that at my business page, as well.

[Jrgunn5150]

You mean bumpers cost money? I'm out.