I was getting a fluttering torque converter clutch. So I did some reading, and the bore on the
PWM valve can open up after a lot of use, which allows pressure flow across the valve, which induces slip, which the computer notices, so it increases pressure to the clutch, which causes the flutter. Feels like a misfire, but only when the TCC is demanded on. The TCC is only demanded on when in 4th gear, or when in manual D3 3rd gear.
Anyways - I decided to tear into the transmission valve body and install a transgo SK 4L60E kit, which is supposed to fix this issue along with making shifts firmer and making other changes that should prolong the life of the transmission.
I actually found the instructional video on the transgo site (
http://transgoonline.com/4L60E_HD2Video.html) to be very helpful, so if you're doing this same kit, watch that first. It really does help.
On to the pictures.
Pan dropped:
Filter removed:
Wiring, TCC solenoid, TCC TWM solenoid, and TFP Valve Pos. Switch removed:
Valve body removed:
Separator plate and 1-2 accumulator removed (visible at top right is the 3-4 accumulator):
Swapping springs on the 1-2 accumulator:
The Isolator/Converter valve that was causing all my troubles, and it's one-piece replacement (lower):
Adding internal spring to the actuator feed limiting valve, inside the same bore as the pressure control solenoid:
Wear in the check-ball holes in the separator plate (replaced the plate):
The hardest part of this kit was getting the retaining ring (221 below) back into the hole in the transmission (still on the vehicle) after changing out the pressure regulator spring. You can see the hole at the bottom left of the pictures of the transmission.
Change out the the low overrun valve spring in the forward accumulator, also visible is the new separator plate (plated and heat treated):
Valve body back in, wiring back in place (be aware, if you do this, there are very specific places these bolts go, and how/where you install them is critical):
Drain plug installed on the clean pan:
Note: trailblazer transmissions have a special filter with a beveled edge on the front left... I'll know for next time!
My transmission now allows 0 rpms of slip when the TCC is demanded on. It used to allow ~100 by design. Also no more TCC flutter, and I'm a happy camper. Shifts are a tad sharper, but not much.
Also included in the kit are a few other things that I didn't show or I didn't change out (mainly because overall, I feel my transmission shifts pretty well).
I hope this may help someone down the road.